CN101521249B

CN101521249B - Manufacturing apparatus and method for large-scale production of thin-film solar cells

Info

Publication number: CN101521249B
Application number: CN2009101264330A
Authority: CN
Inventors: D·R·霍拉斯
Original assignee: Miasole
Current assignee: Fujian Miya New Material Co ltd; Miasole Equipment Integration Fujian Co Ltd
Priority date: 2002-09-30
Filing date: 2003-09-24
Publication date: 2012-05-23
Anticipated expiration: 2023-09-24
Also published as: CN101521249A; CN1703782A; CN100530701C

Abstract

A method of manufacturing improved thin-film solar cells entirely by sputtering includes a high efficiency back contact/reflecting multi-layer containing at least one barrier layer consisting of a transition metal nitride. A copper indium gallium diselenide (Cu(InxGa1-x)Se2) absorber layer (X ranging from 1 to approximately 0.1) is co-sputtered from specially prepared electrically conductive targets using dual cylindrical rotary magnetron technology. The band gap of the absorber layer can be graded by varying the gallium content, and by replacing the gallium partially or totally with aluminum.Alternately the absorber layer is reactively sputtered from metal alloy targets in the presence of hydrogen selenide gas. RF sputtering is used to deposit a non-cadmium containing window layer of ZnS . The top transparent electrode is reactively sputtered aluminum doped ZnO. A unique modular vacuum roll-to-roll sputtering machine is described. The machine is adapted to incorporate dual cylindricalrotary magnetron technology to manufacture the improved solar cell material in a single pass.

Description

The manufacturing installation of thin-film solar cells large-scale production and method

The application is that application number is 03825443.3, the applying date is on September 24th, 2003, denomination of invention is divided an application for the application of " manufacturing installation of thin-film solar cells large-scale production and method ".

The application requires the rights and interests of U.S. Provisional Application 60/415009 that proposed on September 30th, 2002 and the U.S. Provisional Application 60/435814 that proposed on December 19th, 2002.

Technical field

The photoelectric field that the present invention relates generally to disclosed herein, relate more specifically to based on comprise copper, indium, gallium, aluminium and selenium and have the polycrystalline yellow copper structure absorbed layer, be used for unique high transmission rate roll-to-roll vacuum deposition system and method that thin-film solar cells is made.

Background technology

In recent years, in interest development has been arranged to film photoelectric.This mainly is because the raising of the battery conversion efficiency of making in laboratory scale, and with early and more expensive crystalline solid and polysilicon compared with techniques, can reduce manufacturing cost effectively.Term " film " is used to distinguish such solar cell and the more common battery based on silicon, and common silica-based battery uses thick relatively silicon wafer.Though monocrystalline silicon battery is still keeping surpassing the record of 20% conversion efficiency, the performance of the hull cell of having produced approaches this level.Therefore, the performance of hull cell no longer is to limit the subject matter of their commercial application.Now, advancing the business-like most important factor of thin-film solar cells is cost.Current, do not exist to reach the low-cost technical scheme of accepting extensively of making yardstick.

Done and attempted and repaired now problem, but made slow progress.Though to the building window market, there is huge basis in the sputter coating of glass,, because of several reasons, this technology is not easy to be fit to the production of solar cell.The first, the glass of plated film is thick relatively with comparing of in solar module, using in large-scale machines.In addition, must cause huge production loss owing to broken with fracture with glass heats to far above the temperature that needs in the window industry.Aspect floor space and equipment, it is expensive handling structural glass, and the extra layer of solar cell need have the other huge coating chamber of suitable gas barrier between the chamber.At last, the most important thing is perhaps that also do not make effective sputtering target for absorbed layer is deposited as, this is to make the most challenging aspect of thin-film solar cells in many aspects.

In the United States Patent (USP) of publishing March 9 nineteen eighty-two 4318938 (' 938), propose to improve the early stage trial that solar cell is made with the roll-to-roll technology by Paul Barnett people such as (Barnett).The roll-to-roll machine that they describe is made up of a succession of independent batch processing chamber basically, and each batch processing chamber is suitable for the formation of different layers.Through the independent chamber of that string of reception needs layer, supply with the thin foil substrate continuously from spool with the linear strip mode.Form several layers through evaporation in desired material in vacuum chambers.From the atmosphere to the vacuum, return the continuous several times moving metal paper tinsel of atmosphere.This invention is not described this and how to be accomplished, except buying the statement of such technology.In recent years manyly changed.In that ' it is unsettled on the spot that the copper sulfide absorber layers that proposes in 938 has been presented at, and some other layers do not re-use.In more detail, on the coating of up-to-date formation, do not expect to have the pinch roller operation.Yet the inventor estimates that their connecting technique can reduce manufacturing cost and surpass the similar twice to traditional batch processing of silicon.Though today, twice was still very big, more competitive if solar energy will become than the source of conventional energy generation, must realize that bigger cost reduces.

In the United States Patent (USP) of publishing on November 5th, 1,996 5571749 (' 749), Ma Tesuda people such as (Matsuda) instruction is based on the roll-to-roll coat system of plasma chemical hydatogenesis (CVD) technology.Their system is the single linear vacuum chamber that is useful on a string six valves of process isolation.Be similar to ' 938 method, through machine, still whole process reel keeps in a vacuum web substrate with ribbon-like manner.The absorbed layer of solar cell is processed by the amorphous silicon that silane gas decomposes the back deposition.Introduce the different p-n joints that thing needs with generation that mixes along banded path.(Troy, Uni-Solar Michigan) use similar techniques to make various non-crystal silicon solar cells at Michigan's Troy.The conversion efficiency of amorphous silicon battery is inferior to other hull cells, and through the Stabler-Wronski effect mechanism that is widely known by the people, during being exposed to the first few weeks of solar radiation, they are subjected to loss in efficiency.Because this, the efficient of polysilicon keeps being lower than fully other thin-film materials, but also nobody finds the method that alleviates this effect.

In the United States Patent (USP) of publishing on April 16th, 2,002 6372538 (' 538), Wen Te people such as (Wendt) discloses the roll-to-roll system, and its instruction is based on the method that is used for the deposit film solar cell of two copper indium diselenide/gallium (CIGS) absorber layers.This system is described to, and is made up of the individual processing chamber of nine separation, can use the roll-to-roll process in each chamber.Therefore the system of describing in, whole system is similar to ' 938, but there is not to pass through simultaneously the continuous band-shaped transportation of the substrate of being had family.Equally, not as ' constantly supplying with the reel (being polyimides in this case) of thin material in 749 through single vacuum system.The conventional planar magnetron sputtering of Wen Te people such as (Wendt) instruction is used for the deposition of molybdenum base contact layer on polyimide film.Argon pressure is done adjusting, and when the time for CIGS deposition heating polyimides, introduce some oxygen with the stress of regulating film to adapt to the expansion of polyimides.Oxygen is attached in the molybdenum layer resistivity that increases it, needs thicker layer that the conductibility of suitable electricity is provided.Use the hot vaporizer array that respectively deposits a kind of component, in the chamber of separating, on the order layer, deposit the CIGS material.The use of polyimide substrate material proposes two problems at least in processing.The first, it comprises the moisture of quite a large amount of absorption, in vacuum chamber, discharges the moisture of absorption and has passive influence during the course.The second, it is not able to take to be the used higher temperature of the deposition of high-quality CIGS material.The stainless steel thin foil will not have these problems.The first-selected width of polyimide web is 33cm, and under the typical linear velocity of per minute 30cm, moves.As for the present invention, do not think that this speed of production (one square feet of about per minute) is extensive; On the contrary, make solar energy recently competitive from the energy of traditional energy, the reduction of 5 to 10 times of faster speed and incidental post is essential.

Two copper indium diselenide (CuInSe ₂Or CIS) and its more high band gap variant two copper indium gallium selenide (Cu (In/Ga) Se ₂Or CIGS), two copper indium diselenide aluminium (Cu (In/Al) Se ₂) and substitute any of these compound of some selenium, a batch of material of the desired performance that representative is used as absorber layers with sulphur in thin-film solar cells.Once in document, generally used acronym CIS and CIGS.So far the variant that contains aluminium does not also have acronym, so on expanded sense, represent by the gross the alloy based on CIS with CIGS here.Play the effect of solar absorber layer, these materials must be p shape semiconductors.When keeping the chalcopyrite crystal structure, this realizes through the slight deficiency of arranging copper.Gallium replace usually normal indium content 20% to 30% to improve band gap; Yet, great and useful variation are arranged outside this scope.If replace gallium with aluminium, obtaining identical band gap needs the aluminium of less amount.

On substrate (for example glass, stainless steel foil or other function backing materials),, produce the CIGS thin-film solar cells usually through at first depositing molybdenum base electric contacting layer.Through one in two widely used technology, then on molybdenum layer sedimentary facies to thick cigs layer.In pioneer's technology, with physical evaporation deposition (PVD) method (just evaporation or sputter), chemical bath or electro-plating method plated metal (Cu/In/Ga) at first on substrate.Subsequently, earthquake is to about 600 ℃ temperature, and the gas and the metal level that in diffusion furnace, carry selenium react to form final CIGS synthetic.The most frequently used gas that carries selenium is hydrogen selenide, is extremely poisonous to people's hydrogen selenide, and in its use, needs extreme care.Pass through all CIGS components of co-evaporated from the thermal evaporation sources of separating toward hot substrate, second technology avoided the use of hydrogen selenide gas.When the deposition velocity of thermal evaporation is considerably high, the restive stoichiometry that had both obtained to need in source also obtain substrate to go up thickness on a large scale even.To effective large-scale production, these technological neither ones that are used to form cigs layer are marketable easily.

Partly because the CIGS deposition needs high temperature, molybdenum is as the pedestal touch layer.Under the depositing temperature that improves, other metals in CIGS (silver, aluminium, copper etc.) trend towards being diffused into and/or react with selenium, between contact layer and cigs layer, produce unwanted mixing up or the interface.Molybdenum has very high fusing point (2610 ℃), and this helps avoid this problem, although at high temperature it will react with selenium.Yet even make reaction interface minimum, molybdenum and cigs layer still have quite weak reflection on the interface and since initial not through CIGS effectively the reflected back light that penetrates absorber cause the efficient reduction for absorbed second time of chance.Therefore, replace molybdenum can allow to reduce the thickness of absorbed layer, also near p-n junction improved battery performance is provided through moving absorption events with better reflector.

The most often using the n type material of thin to form " window " or " buffering " layer with the CIGS absorber layers is that sulfuration is at a distance from (CdS).It is thinner and be applicable to chemical bath deposition (CBD) usually than cigs layer.Separated is poisonous, and the chemical bath refuse causes environmental disposal problem, the cost of increase manufacturing battery.CBD zinc sulphide (ZnS) successfully has been used as the substitute of CdS, and the battery of production comparable quality.The CBD method that is used for ZnS is equally poisonous unlike CdS; But, keep relatively costly and time consuming treatment step, if possible this should be avoided.On small-scale, demonstrated radio frequency (RF) sputtering sedimentation of CdS and ZnS.Yet control RF sputtering sedimentation is difficult on large tracts of land, because in the conventional method that realizes the RF sputter, the geometry of chamber influences plasma to heavens.The improved method that needs RF sputter ZnS to be to reduce the complexity of handling, and also from handle, removes poisonous separated.

At last, cover window or resilient coating with thick relatively transparent conductivity oxide, the conductivity oxide still is the n N-type semiconductor N.In the past, zinc oxide (ZnO) is as the alternative of traditional but also more expensive tin indium oxide (ITO).Recently, the ZnO of adulterated al has demonstrated and has showed as ITO, and in industry, has become alternative materials.Through the deposition of transparent top conductive layer, before accomplishing battery, usually on resilient coating top " inherence " (meaning is a high resistance) ZnO layer of deposition of thin to cover any plating flaw of CdS (therefore " buffering " layer).In order further to optimize the performance of battery, can apply ARC as final step.Because refractive index is different, this step is more important to silion cell comparison CIGS battery, and wherein certain antireflection level is provided by encapsulating material when battery is made into module.Under the situation of CIGS, apply the anti-reflective film coating can for the outer surface of glass.

In the deposition of relevant absorber layers of CIGS and resilient coating intrinsic difficulty has hindered with economy and the low cost improved and has promptly made these thin-film solar cells on a large scale.In the elimination of back reflection body and cadmium and the common progress on its waste disposal problem, can also reduce the cost of every watt of the solar energy of generation.

Shown in Figure 1 is the CIGS solar battery structure of traditional prior art.Because the huge range on the thickness of different layers is diagrammatically described them.Also pointed out the material that each layer is the most frequently used in the drawings.The arrow on figure top is presented at the direction of solar illumination on the battery.Element 1 is a substrate, and to compare it with the thin layer that on it, deposits be thick and heavy.In solar cell research, glass is general substrate; Yet more possible is will use some substrate types as paper tinsel to large-scale production.Layer 2 is that the back of the body of battery electrically contacts.Traditionally, it is the molybdenum of about 0.5 to 1.0 micron thick.Though molybdenum and CIGS chemistry and CIGS sedimentary facies have shown it is compatible to high temperature, it has some shortcomings.Compare with other better conductor metals (for example aluminium or copper), molybdenum is more expensive, and it is not good reflector in the spectral region of the sun output of maximum.Therefore, first through in the CIGS absorber, not producing the light of electron-hole pair, can not through absorber effectively reflected back cause the chance second time of photoelectric effect incident with supply.The light that comprises the molybdenum absorption of the solar spectrum part that drops on outside the CIGS absorption band only has contribution to the heating of battery, and this reduces its total conversion efficiency.Better the back electrode material is desirable in extensive manufacturing system.

Layer 3 is CIGS p-type semiconductor absorber layer.It is about 2 to 3 micron thick usually, still, if improved the reflection of dorsum electrode layer (2), can approach a bit and obtain identical or improved efficient a little.Through this layer of magnetron sputtering production is very desirable.Because can large scale easily make magnetron, and the control of thickness and composition is fabulous, this makes extensive manufacture process become possibility.The main device of this invention will prove how this can make of the CIGS material.Layer 4 is to have accomplished the n type semiconductor layer that p-n junction forms.Compare with absorbed layer (about 0.05 micron) that it is thinner, and it should be very transparent to solar radiation.Traditionally, because it lets light pass through down to absorber layers, it is called as Window layer.Because as if damage that the deposition that it helps the protection p-n junction to avoid following one deck causes, it also is called as resilient coating.Up to now, the use of CdS has caused the battery to the peak efficiency of CIGS type absorbent material.But CdS is that environment ground is poisonous, no matter is that uniform deposition is difficult on large scale through the chemical bath method or through traditional RF magnetron sputtering.In addition, CdS is not very transparent to the green and blue area of solar spectrum, and this makes it and more band gap absorber layers is not too compatible.

In the 26th IEEE photoelectricity specialists meeting October in 1977, You Laer (Ullal), Wei Beier (Zweibel) and Fan Luodemu (von Roedem) have proposed can be used as 15 kinds of no cadmium inventories that comprise the n type material of CdS layer substitute.In argon and oxygen atmosphere, the common response magnetron sputtering through metal deposits these materials SnO easily ₂, ZnO, ZrO ₂With the ZnO that mixes.Reactive sputtering like the use bicylindrical shape rotating magnetron of instruction in United States Patent (USP) 6365010 (' 010) is particularly useful to depositing these oxide layers.Yet if done equipment improvement to handle the transmission to the reactive deposition district of a small amount of hydrogen sulfide and hydrogen selenide gas, bicylindrical shape rotary magnetron Manifold technology can easily expand to the reactive sputtering of sulfide and selenides.Use this technology, in reactive mode, can deposit two kinds in the other materials, i.e. ZnS and ZnSe on the above-mentioned inventory easily with bicylindrical shape rotary magnetron guard system.In reaching the laboratory demonstration battery of 18% conversion efficiency, used the ZnS replaced C dS of additive method deposition.In addition, ZnS and ZnSe have bigger band gap than CdS, so they are more effective window materials.For depositing the thin layer that can not easily form any retained material that conducts target, the less-than-ideal method of traditional RF sputter will work limpingly.

Layer 5 is top transparent electrode, and it accomplishes function battery (functioning cell).This layer had both needed highly to conduct also need be transparent as far as possible to solar radiation.ZnO is the traditional material that uses with CIGS, but the ZnO of tin indium oxide (ITO), doped with Al and a little other materials can manage it.Layer 6 is antireflection (AR) coatings, and it can allow a considerable amount of additional light to get into battery.According to the desired use of battery, on (as diagram) on the upper conductor or the cover glass that separating or on both, can directly deposit it.To the power supply based on the space, the cover glass of eliminating the throw-weight that increases a great deal of costliness is desirable.Ideally, at the overall optical spectral limit that photoelectric absorption takes place, the AR coating reduces to very approaching zero with the reflection of battery, and increases reflection simultaneously to reduce heating in other spectral regions.Simple AR coating can not cover the wide relatively spectral absorption region of solar cell fully, so must be with more expensive multilayer design more effectively to work.Can carry out the AR function can also increase the coating of the reflection of unnecessary radiation, even more multilayer becomes exquisiter with effective coat system.In the United States Patent (USP) of publishing on August 22nd, 2,000 6107564, people such as Aguilera have looked back previous technology up hill and dale, and some improved AR coated designs are provided for solar cell cover.

Like above-mentioned molybdenum back contact is not good reflector, yet it has become the standard of thin film solar cell.The discovery meeting withstands the better reflecting material of processing conditions differently, can improve battery performance.This task is remarkable.Backing layer should be simultaneously good conductor, can stand high processing temperature, and it should be good reflector.Many metals in the periodic table satisfy these at least one in requiring, and can do any metal to such an extent that enough thickly play the effect that the back of the body electrically contacts so that enough conductivity to be provided.The consideration to low-melting-point metal has been eliminated in the requirement of high processing temperature.Metal as tin, lead, indium, zinc, bismuth, and other the material that is used for CIGS or most of other solar absorbers have just melted in the temperature that is lower than processing temperature.Reduce the motivation of battery cost and got rid of the metal as gold, platinum, palladium, rhodium, ruthenium, iridium and osmium, they have good conductibility and reasonable reflection characteristic in other respects.Except the highly active magnesium, the half of every other metal in a left side is weak relatively reflector in the periodic table of elements, comprises molybdenum.Remaining candidate comprises aluminium, copper, silver and nickel, and has only nickel (with the molybdenum of less degree) opposing to form insulation and weak reflection selenium compound at the CIGS interface.Yet, if allow to diffuse into the CIGS material, the nickel CIGS material of will seriously degenerating.

In order to reduce the cost of thin-film solar cells, and make them more competitive, improve the large scale manufacturability of thin-film solar cells and make us desireing than the conventional source that power supply produces.The use of term large scale means in context of the present invention, the coating of discrete substrate or continuous reel have an appointment one meter or bigger width.The present invention is provided for the apparatus and method of all layers of sputtering sedimentation in solar cell, particularly cigs layer, and it increases depositional area widely, on depositional area, can obtain the also performance of the needs of control material.It also provides the improvement in back of the body contact/reflector, and eliminates cadmium from processing procedure.

Summary of the invention

People such as Iwasaki has introduced the way to solve the problem about traditional C IGS solar cell in United States Patent (USP) 5986204 (' 204).The identical list of the candidate metals of just having discussed above they consider; Yet they advise carrying on the back conductor and use silver-aluminium and copper-aluminium alloy.Use the limitation of these alloys to be, they must be used down in low relatively treatment temperature (being lower than about 120 ℃), and it is barely suitable in the amorphous silicon absorber layers, and is still, inoperative under its normal operation temperature to CIGS.In addition, this invention is taught between alloy and the absorber layers with transparent conductive oxide (ZnO) as the barrier layer, also on distortion Base Metal layer, places alloy to increase angle of scattering.The ZnO layer provides conductibility and suppresses and moves, but all useful transparent conductive oxides of picture, and it is the n N-type semiconductor N.When p type absorber layers is against placed it, form weak p-n junction, the effect of its generation is to apply unwanted little reverse electrical bias to battery.So p-n junction originally must overcome this reverse biasing and flow to cause useful electric current, thereby net efficiency reduces.

People such as Iwasaki are on correct track, but their performance of reflector is had two obstacles.The first, ZnO) barrier layer should not be the n N-type semiconductor N; The second, comparing alloy with simple metal has more weak conductibility and reflectivity usually.In the nitride of transition metal, boride, silicide and the carbide, several have a high electrical conductivity; In addition, they have high fusion temperature and are inactive relatively.Some have desirable optical property.Most optimum materials is the nitride of some transition metal, the titanium nitride (TiN) of saying so in more detail, zirconium nitride (ZrN) and chromium nitride (HfN).Compare with their base metal, these nitride have high fusing point (to about 3000 ℃ of ZrN) and higher electrical conductivity, and their roles are unlike semiconductor.In addition, they have good optical property; Particularly, be similar to the low refractive index of noble metal.In order to form improved back of the body contact/reflector, these character make them very useful in solar cell.All above mentioned nitride roles are fine, but zirconium nitride has a little better optics and electrical properties, and it is discussed at this as the representative of whole type of metal nitride.

Fig. 2 shows from 400 to 1200nm, the reflectivity that molybdenum, niobium, nickel, copper, silver, aluminium and zirconium nitride 0.5 micron thick (opaque) film calculate in air.This spectral region covers the main region of solar radiation output, and it is on the photon energy of about 1 electronvolt (ev).For peak efficiency, be best to the band gap of unijunction solar cell 1.4 to 1.5ev, and the reflection inferior to the reflection of any other metal arranged at this regional niobium and molybdenum.Relatively show its metal person's character with molybdenum, niobium and nickel through the high relatively reflectivity of zirconium nitride.The reflectivity of metal depends on the optical index of air and metal in air, and it changes with wavelength certainly.Simple formula in air/metal interface reflection is:

R = \frac{{(n_{m} - n_{0})}^{2} + k_{m}^{2}}{{(n_{m} + n_{0})}^{2} + k_{m}^{}}

N wherein _oBe the refractive index (～1) of air, and n _mAnd k _mIt is the extinction coefficient of refractive index and metal.Much smaller than one, and extinction coefficient ratio one is big for the metal refractive index of picture silver, so k _m ²Item is arranged, and thick film is reflected near 100%.In the situation of molybdenum, niobium and nickel, n and k are greater than one, so because (n in the visible region _mThe n of-/+ _o) ²The reflection that item calculates them is fully little

Also have an appointment 3 refractive index of most by chance semiconductors, this is especially genuine for two main competitor CIGS of thin-film solar cells absorber and CdTe.The reflection formula shows that back reflection layer should not have and approaches 3 n and k value.As if, in more detail about molybdenum, even if in the industry cycle almost nobody note or this potential problem be discussed.Fig. 3 is presented between cigs layer and metal backing conduction and the reflector, and it is this layer actual acting mode in solar cell, the reflection of the calculating of these metals at the interface.Note, show, greatly reduced its reflection through the factor from the aerial value of molybdenum greater than 2 at the critical spectral regions of majority as above-mentioned.The reflection of niobium and nickel is clearly better a little, but has reduced effectively.It is so not many that the reflection of other metals reduces, because their refractive index is more different from 3.Nickel is than the better reflector of molybdenum, and it is with more economical; Yet the tendency of its diffusion is potential problem, and because it is magnetic, it more is difficult to sputter than nonmagnetic metal.Than molybdenum, niobium or nickel the zirconium nitride of better reflection being arranged will be fabulous solution.Yet, the identical total electrical conductivity like 0.5 micron molybdenum is provided, with the zirconium nitride of about 1.5 micron thick of needs.It is possible utilizing a kind of so thick quite economic film of reactive sputtering manufacturing; Yet, better solution is arranged.

When Fig. 4 shows the thick barrier layer of the 15nm when placement zirconium nitride between cigs layer (or CdTe layer) and metal level, the reflection of the metal in preceding two figure.Though slightly reduced the reflection of other metals, effectively improved the reflection of molybdenum, niobium and nickel.When the thickness of further increase zirconium nitride layer, all metals are in the reflectivity at the interface reflectivity near thick zirconium nitride, (surpassing 70%) as shown in Figure 7.In fact, calculate to estimate the zirconium nitride thickness at about 100nm (or 0.10 micron), the metal level below zirconium nitride is not seldom so that influence that the reflection of light rate that reverses through cigs layer-it becomes fully and is arranged by the character of zirconium nitride.

As an example, Fig. 5 shows when the thickness of zirconium nitride changes from 0 to 200nm, in absorber/reflector interface for molybdenum and the reflection of silver in the wavelength of 800nm.When the thickness of zirconium nitride increased, reflection increased at first sharp for molybdenum, and still, it begins to tilt (roll off) at about 30nm thickness, and changed very slow after about 60nm thickness.Further variation in the reflection of 100nm thickness is imperceptible.Reflection results to niobium and nickel (not having to show) shows with the mode that is similar to molybdenum.Compare with molybdenum and to be reflected in higher level starting, but their are soon near identical limit.

For silver, be reflected in high reflection beginning (about 95%), and cross identical approximately thickness range like the situation of molybdenum, drop to the reflection of thick zirconium nitride.Usually, weak reflector metal needs thicker zirconium nitride, and very good reflector metal should have thin barrier layer, has just just enough done the work of protection absorber/reflector interface.So the ZrN thin layer produces the effect as metal, and prevent the formation of reverse p-n junction.It improves the reflection of weak optically metal, and the protection cigs layer does not receive the diffusion of high-reflectivity metal.Because optical property need be separated with the conductibility of back contact, the confession parent metal layer more selection of wide region is possible.

Therefore, the present invention relates to be used to produce the roll-to-roll precipitation equipment and the method for full sputtered film CIGS solar cell, wherein utilize direct current (DC) sputter to form the CIGS absorber layers through codeposition from rotating magnetron a pair of rectangle plane or cylindrical.Conventional planar magnetron RF sputter ZnS resilient coating from ensconce special chamber is so replace poisonous CdS with more optimum material.Utilize DC and exchange (AC) sputter to form the rest layers the battery through deposition from dual magnetron.So, through no wet processes or do not comprise the big module vacuum deposition machine of high-temperature gas diffusion process, make battery with one-stroke.Through increasing the material that before in solar cell, does not have use, improve back of the body contact/reflector.In the preferred embodiment of this invention; From bicylindrical shape rotating magnetron deposition cigs layer; In the structure that United States Patent (USP) 6365010 (through with reference to it is combined in this) is described, used bicylindrical shape rotating magnetron; A target comprises copper and selenium therein, and second target comprises indium, gallium and selenium or indium, aluminium and selenium.

Main purpose of the present invention provides the large scale manufacturing system that is used for film CIGS solar cell economical production.

The other purpose of this invention provides the manufacturing agreement that is used for solar cell, from operation, has removed high temperature toxic gas and poisonous wet-chemical therein and has bathed.

Another purpose of this invention provides the manufacturing process that is used for the CIGS solar cell, and it has reduced the cost of CIGS solar cell effectively, clearly through in the improvement of the back of the body on the contact/reflector and the eliminating of cadmium and its toxic waste processing.

This is invented further purpose and provides device and the manufacturing process that is used for the CIGS solar cell; It has increased the size of the substrate of ability usefulness effectively; Be included in enhanced capacity and efficient dedicated custom with modular roll-to-roll coating machine on, the fundamentally continuous reel of the material of deposition.

The present invention is a method of making solar cell; It comprises provides substrate; On the surface of substrate the deposit conductive film, wherein conductive membranes comprises the discontinuity layer of a plurality of conductive materials, on conductive membranes the deposition at least one p type semiconductor absorber layer, wherein the p type semiconductor absorber layer comprises two copper indium diselenide (CIS) based on alloy material; Deposition n type semiconductor layer to be forming p-n junction on the p type semiconductor absorber layer, and on the n type semiconductor layer conductivity top contact layer of deposit transparent.

In another aspect of this invention; The method of making solar cell comprises provides substrate; Surface deposition conductive membranes at substrate; On conductive membranes the deposition at least one p type semiconductor absorber layer, wherein the p type semiconductor absorber layer comprises two copper indium diselenide (CIS) based on alloy material; And wherein the deposition of p type semiconductor absorber layer comprises from a pair of conductive targets cosputtering CIS material, on the p type semiconductor absorber layer deposition n type semiconductor layer forming p-n junction, and on the n type semiconductor layer conductivity top contact layer of deposit transparent.

Still in another aspect of this invention; The method of making solar cell comprises provides substrate; Deposit conductive film on the surface of substrate; On conductive membranes the deposition at least one p type semiconductor absorber layer, wherein the p type semiconductor absorber layer comprises two copper indium diselenide (CIS) based on alloy material; And wherein the deposition of p type semiconductor absorber layer comprises coming leisure to comprise the active A C sputter material of a pair of identical conductive targets in the sputtering atmosphere of argon gas and hydrogen selenide gas, on the p type semiconductor absorber layer deposition n type semiconductor layer forming p-n junction, and on the n type semiconductor layer conductivity top contact layer of deposit transparent.

Also one of the present invention more aspect; Solar cell comprises provides substrate; The conductive membranes that on the surface of substrate, deposits, wherein conductive membranes comprises the discontinuity layer of a plurality of conductive materials; On conductive membranes, arrange at least one p type semiconductor absorber layer, wherein the p type semiconductor absorber layer comprises two copper indium diselenide (CIS) based on alloy material; Arrange on the p type semiconductor absorber layer n type semiconductor layer, wherein on the p type semiconductor absorber layer and the n type semiconductor layer form p-n junction, and the transparent conductivity top contact layer on the n type semiconductor layer.

Still one of the present invention more aspect, the vacuum sputtering device comprises the input module that is used for decontroling from a volume backing material backing material, is used for receiving from input module at least one processing module of backing material, and output module.Processing module comprises rotatable coating drum, rouses extensible substrate around rotatable coating; The heater arrays that is used for heating coating drum, and one or more sputter magnetron, each sputter magnetron have magnetron cavity and the numerous conduction sputtering targets and each sputter magnetron that are arranged in the magnetron cavity are used for sputter material on backing material towards the coating drum.Output module receives backing material from processing module.

Through the review of specification, claims and accompanying drawing, other purposes of the present invention are closed characteristic will become obvious.

Description of drawings

Fig. 1 is the sketch map of the prior art structure of basic CIGS solar cell.

Fig. 2 demonstration it has been generally acknowledged that the reflection that the useful metal as the solar cell back contact calculates in air.What comprise is the new classification material by the zirconium nitride representative.

Fig. 3 is presented at the internal reflection that calculate at the interface between CIGS absorber layers and metal and the zirconium nitride shown in Figure 2.

Fig. 4 is presented at the internal reflection of calculating on the interface between CIGS absorber layers and the metal shown in Figure 2, and on the interface, is placed with the thick zirconium nitride layer of 15nm.

Fig. 5 shows as the function of zirconium nitride thickness, in solar cell on the absorber/reflector interface in the reflection of 800nm.

Fig. 6 shows the structure of basic solar cell of the present invention, wherein leads at cigs layer and back pass/insert zirconium nitride between the reflective metal layer.

Fig. 7 shows the structure that supplies solar cell of the present invention to select, and has wherein improved back pass with copper and silver layer and has led/reflector.

Fig. 8 schematically shows the cosputtering from the CIGS material of traditional two rectangular planar magnetrons.

Fig. 9 schematically explains the preferred embodiment from the DC cosputtering of the CIGS material of bicylindrical shape rotating magnetron.

Figure 10 schematically shows the method for using AC power supplies cosputtering CIGS material chosen property.

Figure 11 schematically shows the active sputtering method of selectivity AC with the CIGS of metal alloy targets formation likewise material, use bicylindrical shape rotating magnetron.

Figure 12 schematically explains with three cover dual magnetrons to increase deposition and grade, its band gap of composition change of cigs layer.

Figure 13 shows the preferred embodiment structure of the full sputtered version of improvement of basic solar cell of the present invention.

Figure 14 shows the sketch map of high simplified of the end view of the roll-to-roll module sputter machine be used to make the solar cell that Figure 13 describes.

Figure 15 shows that coating rouses and the more detailed sketch map of the processing module sectional view of the CONSTRUCTED SPECIFICATION of magnetron.

Embodiment

Now, will describe the present invention, and do comparison with the structure of the CIGS solar cell of traditional prior art.With new battery structure and manufacturing process that the modularization package sputtering depositing system of realizing about the best that is designed to provide operation particularly is detailed.

Should note; As used herein; Term " ... on (over) " and " ... on (on) " both comprise inherently " directly exist ... on " (not having intermediate materials, unit or spatial placement betwixt), and " exist indirectly ... on " (intermediate materials, unit or spatial placement are betwixt).For example, " on substrate " forms the unit, can be included in directly to form the unit on the substrate, do not have intermediate materials/unit therebetween, is also included within and forms the unit on the substrate indirectly, and one or more intermediate materials/unit are arranged therebetween.

Fig. 6 explanation is according to one of basic solar cell of the present invention simple embodiment, and it comprises zirconium nitride.Except the zirconium nitride 2a that between cigs layer 3 and electric contacting layer 2, increases, this figure is similar to traditional solar cell shown in Figure 1.Like above-mentioned suggestion, now electric contacting layer 2 possibly be any metal discussed above or metal with economy of suitable conductivity.Because zirconium nitride will stop diffusion when keeping good reflectivity, by people such as Iwasaki in that ' alloy of advocating in 204 will work.Fine silver will give best performance; Yet it will be relatively costly solution.Aluminium is the most cheap good reflector, but with other its fusing point of compared with metal low relatively (660 ℃), and it absorbs oxygen from the steam of background in vacuum system, this reduces its conductibility.

The alternative embodiment of solar cell of the present invention is as shown in Figure 7, is made by copper rather than molybdenum at that electric contacting layer 2.Copper is relatively cheap and is good conductor.About 0.2 micron thickness, copper provide the conductivity like 0.5 micron molybdenum.Layer 2a is the zirconium nitride thin barrier layer, has the thickness of about scope of 10 to 20nm.At this point, the structure of layer and can be used it with this form as the structure of in Fig. 6, being discussed, because the band gap of its appropriateness, especially with CIGS.Yet through at the thin layer 2b (40 to 50nm) of the silver of the deposited on top of zirconium nitride layer and the additional barrier layer 2c of the zirconium nitride between silver and cigs layer, the (see figure 4) that can remedy about 600nm is in the lower reflection of short wavelength.Use this structure, the reflectivity curve that internal reflection and Fig. 4 acceptance of the bid at silver/ZrN/CIGS interface is marked with " silver " almost is undistinguishable, has avoided a large amount of uses of expensive silver.If the processing temperature of CIGS can reduce from current about 550 ℃ value effectively, can remove the intermediate barrier layers 2a between copper and silver so because temperature be lower than 550 ℃ of copper with silver with rapid counterdiffusion mutually.In addition, to enough low processing temperature, aluminium can replace copper and silver.Certainly, if substrate is metal forming rather than glass, under the situation of the reflectivity that keeps necessity, the Base Metal layer can be done thinlyyer, because metal forming will provide most conductibility.

Following one deck of describing is the absorber layers of CIGS.In the present invention; Preferred deposition process to the CIGS material is a dc magnetron sputtering;, exchanging the reactive magnetron sputter also is feasible alternative method, only reduces this technology use owing to having increased the needs of handling a small amount of poisonous hydrogen selenide gas.As optimal method, two kinds of methods are all utilized the magnetron technology of ' 010 instruction; Although for traditional planar magnetron, in fact this invention possibly not be very effective.It is the semiconductor property because of it that dc magnetron sputtering does not also utilize a reason of CIGS material, and the conductibility of electricity is too low.Direct current sputtering need be as the conductibility of the electricity of metal, and the conductibility of the heat that also need get well is to allow to be used for the high power of high deposition rate.Conceptive, an important viewpoint of this invention is with CIGS material separated into two parts, and each several part all has the character of the manufacturing of allowing the conduction sputtering target.For most semiconductors of the real candidate that in solar cell, is used as absorber layers, this is impossible, and it works still nearest experimental result proof for CIGS.After the trial of the failure of various combination, if find that promise materials processing is suitable, copper and selenium can be combined into conducting base (matrix) several times.If cold pressing and in temperature (217 ℃) annealing a shade below the fusing point of selenium, the very high conductivity of homogeneous mixture maintenance of the powder of forming by about two parts of selenium and a copper.Small sample 208 to 210 ℃ of making has good physical strength, and resistance is less than 1 ohm.When annealing temperature rises to about 400 ℃ when spending, as from CuSe ₂Formation desired, increase in resistance is above 1,000,000 times.It is consistent that but the conductibility of lower temperature material is difficult to the Cu-Se binary system phase diagram.If the chemical reaction between low temperature thermal oxidation Cu and Se does not take place, can to take on bonding be one with the copper matrix that keeps high conduction to Se so.Because this is the sort of situation, will have to spread rapidly at low temperature thermal oxidation Cu, this is unlikely.Cu ₂Se is the Cu/Se phase of unique known conduction mutually, then it possibly form, although it seems inconsistent with the phasor of this synthetic and temperature.Yet as if because annealing back material changes its profile, it supports the reaction that taken place.Do not produce the matrix of high conductance with the similar experiment of the alternative Cu of In.In fact, even at low temperature thermal oxidation, resistance increases with the content of In.Because In and Se have low fusing point, can expect the result that observes, and different with copper, it is consistent with the In-Se phasor.

No matter with the inconsistency of phasor, Cu/Se has been made into consistent with the essential attributes of high speed DC magnetron sputtering.For the target of all the other materials, must comprise In and Ga that needs are accomplished the CIGS structure.In and Ga fuse into one easily forming solder, and it can be poured into a mould or be casted in the mould of backing (backing) or conducting tube to form target.In order to prevent the formation of segregation and low temperature eutectic, need good mixing and quenching rapidly.Better method is to form target through pressed metal powder, in more detail, comprises that Ga is as gallium selenide (Ga ₂Se ₃).Target keeps conduction and has avoided low temperature eutectic.The In that in addition, also can add Se and react and insulate to form with In ₂Se ₃Phase, still, as long as the enough free In of residue conduct matrix to form, target is with sputter fully.Because per two In or Ga atom are needed three Se atoms, and only about half of In/Ga target can be Se, and keep enough conductibility with sputter.Can improve eutectic melting point in fact with the aluminium substituted by gallium, and can not cause any further technical difficulty.Except the selenium from the copper target, the selenium that in In/Ga or In/Al target, comprises provides the overvoltage of selenium during very desirable deposition process.

Another advantage that this target structure technology provides is, with many different methods of removing dopant material with potential useful means.For example, for a long time, well-known sodium (Na) very in a small amount joins the performance that can improve it among the CIGS.At first, noticing at the battery of making on the soda-lime glass has higher efficient than the battery of on other substrates, making, especially stainless steel.Found afterwards that the Na of the trace in deposition process in the glass had diffused into CIGS.Yet the verified method that the non-glass substrate is easily added the sodium of a small amount of but controlled quantity is difficult.With target formation method of the present invention, the NaSe2 with trace (for example about 0.1%) introduces Cu/Se or In/Ga/Se easily, to obtain conceivable doping in absorber layers.

Do the explanation of following sputter CIGS material about a pair of sputtering target: be made up of Cu and Se for one, another is In, Ga and Se.Cu is 1: 2 to the ratio of Se approximately, but can change variation and the needs to adapt to operation.Change In to the ratio of Ga changing band gap, and it can change from independent In (band gap of 1ev) to about 30%Ga (band gap of 1.3ev).Should be noted that the variation, and the same of the ratio of material in each target with the additives of the little level of the doping (aforesaid sodium) of other elements, be considered to invent basically consistent.

Traditional DC rectangular planar magnetrons cosputtering of CIGS material is schematically illustrated among Fig. 8.View is the cross section with the axis of magnetron.The main body of the magnetron that unit 7 expression is traditional, it holds the magnetic module (less than illustrating) of the device of " racetrack " that form sputter and cooled target 8 and 9.Directed magnetron is so that crossing at substrate 10 perpendicular to the line of each target, and its about 10cm is far away.Give each magnetron power supply by DC power supply 11, it is grounding to chamber wall/shield 12 as system anode.As selection, common technically, can provide and the allo anode that separates of each magnetron (not diagram).Between magnetron, place baffle plate 13, react to help restriction to be deposited on from the material of a source sputter on the material in another source or with it.The material that reaction has taken place insulate to a great extent, and is undesirable therefore, and it was blocked in the zone of the flat target of not sputter owing to the past along with the time.Baffle plate should be so not far away to the substrate protrusion, significantly reduces to such an extent as to arrive the flux of substrate.If ground connection, like what indicate, it can play the effect of anode or segment anode to each magnetron.All sputter procedure are used the working gas that almost is commonly argon gas because it is an inertia, can drawing-in system Anywhere.In Fig. 8 to 12, do not show the argon gas injection phase clearly; Yet, at the rear portion of magnetron or sidepiece to inject be conventional with suitable.

Still with reference to 8, one targets of figure, for example 8, comprise conductive material Cu/Se, and target 9 comprises the In/Ga/Se material of conduction.Temperature between 10 to 400～600 ℃ of the heated substrate, and as arrow indicated at the uniform velocity to transmit magnetron.Under the pressure of about 1 to 2 millitorr, introduce argon gas as working gas, and apply DC power supply with sputter material.Regulate a power supply (11) to obtain one acceptable sputtering raste in two targets.Then, regulate another power supply, the not enough synthetic of suitable copper is arranged up to the coating that on the substrate of heating, reacts.If several kinds of compositions in each target have identical sputter profile pattern (although two target patterns can be different each other), through the independent adjusting of power supply, just can obtain suitable synthetic so.Generally speaking, situation partly has different sputter patterns because of single unit not exclusively like this.Therefore, can preferentially collect a composition on the nigh screen, from the transfer coated slightly component of coating ingredients from the expectation of the component of initial target.Adjusting in the synthetic of each target through having only a few percent is with correcting action; But synthetic relies on many factors accurately; The geometry, sputtering pressure and the sputtering power that comprise machine are so must calculate appropriate synthetic to each unique machine construction.In case confirmed synthetic, they just keep constant has had change up to operation or system geometries.The little variation of the synthetic of the target of this adaptive system geometry is considered to fall within the scope of the present invention.

Like the situation of extensive manufacturing operation, when long-time section sputtering target, progressively show with rectangular planar magnetrons embodiment working-procedure problem.Along with the carrying out of deposition process, splatter groove 14 (dotted line) forms the profile of delineating out " racetrack " gradually on each target.Well-known cosine distribution, it describes local flux emission pattern, is orientated vertical with emitting surface.Therefore, along with target receives corrosion and groove formation, little by little change in the substrate Flux Distribution.If the patterns of change of two magnetrons is asynchronous each other, the CIGS material composition that on substrate, deposits will change in time, needs almost to confirm continuously to regulate and be applied in the operation.

Second problem is during long-term running time, and baffle plate 13 can not stop the flux between the target mixed fully.This means that the product of final a large amount of SI semi-insulation will be stopped up the edge of (for example " racetrack ") in the zone of the target of sputter not.This can cause arcization and defective in the CIGS film.At last, from about range of 25% to 40%, and must often change them, so just improve manufacturing cost the utilance of flat target target material.

If in Fig. 8, with columniform rotating magnetron replacement planar magnetron, structure becomes as shown in Figure 9, and wherein common comes mark with similar unit with same numeral.If biconditional operation planar magnetron structure is equally operated them, just can eliminate the problem of getting in touch to a great extent with the magnetron on plane.Because their rotations just will never form the sputter groove.Because it is fixing that the emission mode of flux keeps, so along with the consumption coating composition of target material keeps constant.Also because rotation and the continuous target cleaning in back do not belong to like ' the obstruction of the material that reacts of the long-term increase of the reactive sputtering that specifies in 010 because same reason does not have on target.Because this reason, baffle plate 13 (shown in the dotted line) is not as so important in rotating magnetron embodiment.If the target diameter of rotation equals the width of flat target, and target material has identical thickness, and rotary target has and surpasses three times the initial inventory like the material of flat target so.And because utilance surpasses the twice of flat target utilance, before the needs target changes, rotary target will move the time that surpasses six times of flat targets.This is effective cost savings factor to extensive manufacturing.

Plane or rotating magnetron all can move in the AC pattern.To rotating magnetron, this explains in like Figure 10, but this structure is applicable to planar magnetron too.Replace two DC power supplys 11 with single AC power supplies 15.In order to change deposition between the target, must in a branch road of AC power supplies, insert variable impedance load 16 to keep the not enough film component of copper.Because the anode that the AC of dual magnetron operation need not separate, locular wall/screen 12 no longer needs ground connection, and baffle plate 13 does not need ground connection yet.When conductive targets is supported the DC operation, use this rotating magnetron that optionally is configured to of AC power supplies that advantage is provided hardly, but because the magnetron on plane self-cleaning not, it can provide some protections to prevent arcization in the sort of structure.

As mentioned above, if making, equipment disposition handles hydrogen selenide gas in a small amount or other potential available gas, sputter is a feasible selection to the AC reactive sputtering of CIGS material for DC.Figure 11 shows this structure to a pair of rotating magnetron.It is different from structure shown in Figure 10 in many aspects.At first,

target

8 and 9 is identical now, by the alloy composition through metallic copper, indium and the gallium (or aluminium) selected, to supply with copper not enough a little synthetic and conceivable band gap.Basically, copper adds the atom of gallium or aluminium to indium ratio should be slightly less than 1, and indium is confirmed band gap to the ratio of gallium or aluminium.Use traditional melting and foundry engieering to make metallic target.Because target is identical on composition now, also can remove baffle plate 13.Except using argon gas as traditional sputter gas, for example send into hydrogen selenide gas through near the system of nozzle 17 substrate, in continuous operation with sputter metal atoms generation chemical reaction and form the CIGS material.

So far, the best candidate material of thin-film solar cells absorber comprises the material that must make with labyrinth efficiently, or forms or use the poisonous compound and the material of gas.At present, have one type of material to demonstrate some prospect that changes this situation, these materials are nitride of IIIA family element aluminum, gallium and indium.The nitride of the different mixing of In/Ga and In/Al demonstrates the bandgap range of crossing over the solar spectrum scope.Up to the present, the semiconductor technology that is used for being made into the p type to them is imperfection also.For the production with ' 010 rotating magnetron, such absorber system is desirable.Except replace the poisonous reacting gas hydrogen selenide that kind shown in the structure image pattern 11 with harmless nitrogen.Accurately form transition metal nitride layer previously discussed (ZrN just) by this way.

Because cigs layer (or other absorber layers) is thick relatively, through using two or the many production capacity that can improve the sputter machine to the magnetron that is used for sedimentary deposit.Because comparing the cost of magnetron with the complete cost of vacuum system is appropriate, the productivity ratio of increase surpasses the compensation that the appropriateness on the original capital cost is increased.In-line machine (in-line machine) for applying discontinuous substrate also can improve production capacity through all placing magnetron source in the both sides of machine, and one time applies two substrates.Use many magnetron to be demonstrated another chance with the needs of the deposition rate that increases cigs layer, this develops in the present invention.Use representational example this to be done discussion below.

Figure 12 schematically explains the CIGS deposition region in the sputter machine of (the not having diagram) magnetron that is equipped with three pairs of rotations (illustrating) or plane.It can represent the zone from a row formula machine, if perhaps arrange with arc, then expression carries the zone of the package coater that is installed in the web substrate on the drum.About the direction of motion of substrate 10 (by the arrow indication), first pair of magnetron is 18, the second pairs 19 and the 3rd pair 20.Each to magnetron in, in the target one is the Cu/Se that the synthetic of the suitable adjusting of as above discussing is arranged.Yet, second target in each group can be for example just In/Se to 18, In/Se that 15%Ga arranged to 19, In/Se that 30%Ga is arranged is to 20.By this way, progressively classification of the content of the Ga of cigs layer does not from bottom to top almost have or does not have Ga at bottom section, and at upper area the Ga of certain maximum is arranged.This will be from about 1ev of bottom to the about 1.3ev graded bandgap near the top of layer.Put upside down target sequence or will change bandgap graded in the other direction to apply.Through magnetron being put together enough closely to allow on their depositional model some overlapping, certain of border that can obtain classification is level and smooth.Yet, in any case the interface of the thermal diffusion of material between the zone will cause certain classification.

Through using many group targets, the advantage that can easily regulate the C1GS synthetic is, band gap that can designs C IGS is to optimize battery efficiency.Traditional knowledge possibly advised, as employed in the multi-link battery, forms the highest bandgap region with same order in layer on top, and forms minimum bandgap region in the bottom.Yet through widening the voltage gradient of passing absorber, this structure of in fact in single connection battery, reversing causes the raising of efficient usually.Band gap is not 1 electron-volt (ev) approximately when in CIGS, having Ga (or Al), and for solar spectrum optimum be about 1.4 to 1.5ev.Adopt 30%Ga to replace In to improve band gap to about 1.2ev.Further add Ga and begin to reduce battery efficiency.If Ga all replaces In, band-gap energy surpasses 1.6ev.It is faster than Ga that aluminium improves band gap, is no more than 30% and allows 1.45 band gap.Substitute some selenium with sulphur and can also improve band gap, but than Ga weak effect.Many combinations are possible, and when such as here description ground when making, for the material of the interpolation of wide region, keep enough conductibility with cosputtering through DC method target.If can improve the nitride of p type, can use the ratio of different In/Ga and In/Al to make magnetron target, obtaining the band gap of similar classification,, can realize it through standard reaction AC sputter with nitrogen as ' 010 described.

Since toxicity relevant and waste disposal problem with cadmium, plating CdS n type window or resilient coating that need not be traditional.As what before mentioned, zinc sulphide (ZnS) is acting substitution material about the same.The AC reactive sputtering of the target through the element zinc from the structure that Figure 11 describes, used can be made this material in the present invention easily.In this case, the reacting gas that injects from nozzle 17 is hydrogen sulfide rather than hydrogen selenide.Because hydrogen sulfide also is a kind of gas of danger, it is not the method that is used for the selection of sedimentary deposit.Because layer is very thin, can the RF sputter and can not bring any negative effect to manufacturing speed.Yet, as what mentioned in the past because the non-uniformity that interrelates with the geometry of different machines, big in scale traditional RF sputter demonstrate challenge.The RF sputtering method that describes below will overcome the shortcoming that variable-geometry demonstrates.Use the same RF sputtering technology can RF sputter ZnSe, though two kinds of materials all have the band gap bigger than CdS, because the band gap of ZnSe is less, ZnSe be desirable not as ZnS.

Since most of transparent conductive oxides are n N-type semiconductor Ns, can't be as semi-conductive traditional zinc oxide (ZnO) of n type as Window layer to make PN junction, this is a little a mystery.All previous tests of doing this have all been failed and have been failed to produce high efficiency battery, only if between absorber and ZnO, place CdS " buffering " layer that electroplates.Though also can form indium oxide and selenium oxide, some researchs have been pointed out in the formation of the interface oxidation gallium part at least as problem.At initial ZnO coverlay growth phase,, can cause oxidative damage to the interface through the high energy negative oxygen ion from sputter plasma bombardment CIGS surface.Likewise, energetic ion can cause physical damnification to the interface.

Before applying transparent conduction coverlay, use the thin sacrifice layer of ten minutes that is placed on the simple metal on the cigs layer, can minimize or remove interface damage to PN junction.As everyone knows, the doping of zinc, cadmium and mercury will change CIGS from p to the n type, but having only zinc to be actually does not have toxicity and treatment of wastes produced problem.If use the thin layer of zinc, it can play double action.At first, it can diffuse into the cigs layer doping, and its becomes n type, therefore PN junction is removed from the interface, forms homojunction.The second, in operation, the impact of its ability " acceptance " anion bombardment is transformed into ZnO or ZnS, perhaps removes the damage to the CIGS interface thereby reduce.Injury to the interface is not necessarily limited to energetic oxygen ions.With the pattern similar with oxygen, sulphur and selenium both form energetic ion in sputter plasma.Except the zinc metal all possibly use; Yet they can form the PN heterojunction.For example, the thin layer of some transition metal will protect CIGS to avoid oxidation, but can not move PN junction through diffusing into CIGS.In more detail, zirconium will change into zirconia, and it also is a N type semiconductor, and is one of alternative material of being mentioned by Ullal, Zweibel and vonRoedern.

As the use of the sacrifice layer of just having described can help to protect PN junction, and keeps passing the high voltage of depletion region.Because the ZnO of high conduction will not support the stability in hole, the N type boundary material of low conduction too, so it is useful.Because of this reason, be to use and to be called " inherent " ZnO or i-ZnO initial thin coverlay, with what become convention to help to remain on the loss region that chemical bath is electroplated the zone of CdS pettiness as CdS.Through the more oxygen of adding in the operation of making littler conductibility and material transparent form more, make the ZnO of this form.Certainly because of energetic oxygen ions, the use of independent i-ZnO can damage the interface.Therefore, as long as the oxide of producing is the n-N-type semiconductor N, expendable metal layer just can be replaced traditional plating CdS.

Suitably form with after producing PN junction the electrode layer of deposition top transparent at n type layer.Transparent and the conductive form of ZnO has been the traditional material as this layer, compares with the material of widely used picture tin indium oxide (ITO) in display industry, mainly is because its low cost.ZnO is lower than conductibility and the thermal stability of ITO; Yet when keeping the many cost advantage of ZnO, the ZnO of adulterated al has the similar characteristic of ITO.The level that obtains the needs that this result's aluminium mixes is about 2% o'clock.Other alloys of analog quantity have shown almost also work (consulting " new n type transparent conductive oxide " that T.Minami mentioned in the MRS report in August, 2000).At present, in display industry, main through using the plane ceramic target to accomplish the extensive sputter of ITO, the plane ceramic target has conductibility but makes very expensive.Almost not success of the control of large-scale reaction process when using metallic target.There is similar problem in extensive control to the reaction process of deposition of aluminum doping ZnO.Like what do, can address this problem through using ceramic target, but the extra cost of the manufacturing of target can be offset the many advantages that obtain from more cheap material in principle with ITO.As in that ' rotating magnetron in this invention described in 010 allows the use of cheap metallic target, and the necessary control to the reaction process of large-scale implementation is provided.Reactive sputtering structure is identical with Figure 11 description, and it hits 8 and 9 is metallic zinc targets of suitable adulterated al.Except common argon sputter gas, to crystallizing field oxygen is provided through nozzle 17.

Figure 13 shows the preferred full sputter CIGS solar battery structure of the present invention.Layer 1 (substrate) is high-temperature metal or polymer foil.To the production of energy on land, stainless steel, copper and aluminium are preferred metal formings, and to the space energy source use, very thin titanium and polyimides are preferred metal formings.Describe like Fig. 7 of front, electrically-conductive layer 2,2a, 2b and 2c are respectively Cu, ZrN, Ag and ZrN.As shown in Figure 12 and description, through the variation on the synthetic of continuous target, the CIGS of layer 3 has the band gap of classification.The method of deposition can be the DC cosputtering film shown in Figure 9 or the sputtered film of the described reaction of Figure 11.Semiconductor layer 4 is CdS that the ZnS (or ZnSe) of RF sputter replaces conventional batteries.As another characteristics, layer 4a possibly comprise that as expendable metal layer it becomes N type semiconductor according to later reaction in the deposition process of following one deck (just with oxygen, sulphur or selenium).Layer 5 is transparent top electrodes, is made up of the ZnO of the adulterated al of reactive deposition, to utilize the improvement of traditional ZnO on performance.As explained before, the extremely thin part of ZnO of adulterated al possibly have more high resistivity at the interface of layer 4, connects voltage to improve.Layer 6 is optional antireflection (AR) films, and is actually multilayer heap (not having diagram) is designed to optimize light in battery absorption.Such AR heap will use in the space energy source use, and the there is not a problem from the degeneration of the environment of weather.Use for land, in the module of sealing, (do not illustrate) basic battery of lamination (layer 1 is to layer 5) to the cover glass cover plate, and if use, to the exterior applications AR layer of glass cover-plate, rather than directly give battery applications.Sputtering current collecting net ruling in addition on the conductive oxide at top, and if substrate be metal forming, possibly go up the sputter wet layer of thin welding (a for example tin) overleaf.

Figure 14 explanation be to be used to make the simplified, schematic, side elevation view of package module sputter machine of the improved solar cell of Figure 13.In direction, according to the sized machine, to be supported in the substrate between about two and four feet wide perpendicular to plan.This width is not a basic device-restrictive; On the contrary, recognize the practical difficulty of qualified backing material of the volume of the bigger width of acquisition.Machine is equipped with output or unloading, the module 21b of input or loading, module 21a and symmetry.Between the input and output module, be process module 22a, 22b and 22c.Can change the needs of the quantity of process module with the coating of coupling production.Each module has pump unit flowing with working gas during essential vacuum being provided and handling coating operation.Bottom in each module schematically indicates vacuum pump through unit 23.Real module has many pumps that are placed on the position of other selections, with the suction of working gas that optimization is provided.To the application's turbomolecular pump of high productive capacity preferably.24 places link together module in slit valve, and slit valve 24 comprises very narrow low conductibility insulation seam, prevents that working gas from mixing between module.Further increase insulating properties if desired, can aspirate these seams discretely.As selection, can so that module region to be provided effectively,, to increase module in the time after a while so and become difficult more in the single big chamber of internal insulation if still the operation evolution needs.

Each process module all is equipped with the spin coating drum 25 of supporting drum substrate 26 above that.Array around each coating drum is one group of bicylindrical shape rotary magnetron tube chamber 27.Bicylindrical shape rotating magnetron substitutes traditional planar magnetron; Yet, can lower efficiency, and through the operation operation also can be unstable for a long time.The coating drum can be a bit bigger or a little bit smaller than five of explanation among the figure, to adapt to the magnetron of different quantity.Through the web substrate 26 in the cylinder 28 control entire machine.In real machine, can use more guide pulley.Here those that show are that minimum demand is to present the related description of operation.In actual machine, some cylinder deflection to be launching reel, and some move so that operating the rudder of reel to be provided, and some provide the tension feedback of reel to servo controller, and other only is idle pulley with at desirable position running reel.On entire machine, through feedback signal active drive and control I/O bobbin and coating drum, to keep reel at constant tension force.In addition, the input and output module respectively comprises reel bonding land 29, there, can cut off or connect reel head or tail part, to make things convenient for the loading and unloading volume.Need according to operation, provide the place of reel heating to settle heater arrays 30 at needs.These heaters are quartz lamp matrixes of high temperature, are designed to cross the width layout of coating drum (perhaps reel).Infrared sensor provides feedback signal with servo lamp power and the even heating of passing above-mentioned drum is provided.In addition, coating drum 25 is equipped with inner controlled current or other liquid, so that web temperature regulation to be provided.

Input module adapts to web substrate on big bobbin 31, and it is suitable to metal forming (stainless steel, copper etc.), to prevent material deformation between the storage life.Output module comprises that similar bobbin is to take up reel.The substrate reel of cleaning at first arranges 30 through the heater among the module 21a in advance, and this provides enough heat to remove the water of surface adsorption at least.Subsequently, reel is crossed bobbin 32, and it can be special bobbin, is configured to cylindrical rotating magnetron.When its passed through the roller/magnetron that centers on, this allowed the surface through DC, AC or RF sputter continuous wash conductivity (metal) reel.On screen 33, catch the sputter cylinder material, it periodically changes.If desired, can increase the back side of another roller/magnetron (not having diagram) with cleaning web.The direct sputter clean of conductive web will cause the identical electrical bias on the reel that appears at entire machine, possibly be undesirable according to these other parts at machine of special operation that relate to.Through using linear ion rifle rather than magnetron sputtering to clean, perhaps the big roll coater of packing into (roll coater) separating before than small machine in accomplish and clean, can avoid this biasing.Likewise, corona glow discharge processing can be carried out in this position and electrical bias can be do not caused.If reel is a polyimides, the electrical bias of material can down not transmit through system.Yet polyimides contains too much water.For purpose that adheres to and the desorption that limits water, increase the thin layer of metal (particularly chromium or titanium) routinely.The similar problem that this makes conduction surfaces have on metal foil substrate, to run into.

Below, reel passes valve 24 and gets into the first process module 22a with low conduction insulation seam.The coating drum maintains suitable process temperature by heater arrays 30.Along with the rotation direction (arrow) of drum, two magnetrons that the overall stack in reflector begins at first deposit basic copper layer (like 2 among Figure 13).Next magnetron provides thin ZrN layer, and then is thin silver layer and last thin ZrN layer.To the CIGS absorber layers, band gap is sufficiently low, makes thin silver layer and last thin ZrN layer almost not obtain whatever.Can only form at this situation reflector by a basic copper layer and a ZrN layer.More high band gap materials can benefit from extra silver and ZrN layer in the future.

Be the deposition of the cigs layer of p type classification, reel gets into next process module 22b then.Heater arrays 30 is kept drum and reel in the process temperature of needs.When following three magnetrons were cut down the layer that the amount of galliums (or aluminium) increases, first magnetron deposited two copper indium diselenide layers, thereby increases as previously mentioned or graded bandgap.Through arranging same set of magnetron again, classification can be reversed.Last magnetron in the module passes through from planar magnetron or expendable metal layer RF sputtering sedimentation n type ZnS (perhaps ZnSe) thin layer, and expendable metal layer becomes the part of top n type layer and limits PN junction.

Then reel shifts into last process module 22c, and heater arrays 30 is kept suitable process temperature once more there.The thin layer of first magnetron deposition of aluminum doping ZnO, it has higher resistance to coordinate with the layer that forms and keep PN junction and front.Four remaining magnetron sedimentary facies are to thick, aluminium doping ZnO layer high conductance and transparent, and it accomplishes top electrodes.Can increase extra magnetron station (not diagram), be used to use endless belt mask sputter gridline around the magnetron rotation.If the AR layer is placed at the top at battery, machine will have other process module, will deposit suitable layer heap therein.Extra module can also be equipped with mobile, metal grate and the bus of template to be provided for top electrodes is electrically contacted that scrolling is compatible, shielding.Extra module and shielding device have greatly increased the production battery cost, and perhaps only the value added applications as the space energy resource system are proved proper.

At last, reel gets into output module 21b, here it be wrapped in take up bobbin on.Yet, can carry out other operation here, this is useful in the operation of the battery of after a while entering module.Bicylindrical shape rotating magnetron 34 becomes with the prewet unit at the back side of substrate foil of scolder.Metallic tin perhaps has the best character of the available solder materials of using with the stainless steel metal paper tinsel, still, has many also with acting solder formulations.If keep its cleaning, perhaps Copper Foil is prewetted is necessary.With similar, in output module, before solder spatter, can also do the ion gun sputter precleaning at the back side of paper tinsel at input module.In addition, barrel temperature must be lower than the fusing point (tin is 232 ℃ approximately) of the scolder of prewetting.

Figure 15 shows typical process module, and the amplifier section of the details that shows coating drum 25 and magnetron cavity 27 is arranged.The coating drum is built into and has the double-walled that limits gap 35, and refrigerating gas or liquid can pass the double-walled circulation to regulate the temperature of drum and reel 26.Keep reel and the outer surface close contact of rousing.Magnetron cavity 27 is made up of the rectangular chamber 36 of part, and chamber 36 comprises rotating magnetron 37 and 38 and the mounting hardware that is associated (not diagram).Whole chamber can be positioned at apart from the surperficial variable of coating drum and reel but unified distance is represented by gap 39.This variable gap allows the control of the sputter gas stream of the big process module 22a of 36 entering from the chamber, and it is aspirated fiercely.Thereby, keep big pressure differential between background pressure in rectangular chamber 36 and the process module (22a), and isolate each magnetron and adjacent magnetron effectively.Through one group of evenly spaced pipe 40 of the length along it, in chamber 36, supply with the argon sputter gas, indicate by arrow.To reactive sputtering, organize along the equally spaced two groups of pipes 41 of its length supply response gas in chamber 36 (for example oxygen, nitrogen, hydrogen sulfide, hydrogen selenide etc.) through each.Interior panelling 42 generation passageways, passageway also prevent to change along with time coating flow the conducting path of gas with the reacting gas substrate that leads, and guarantee the operation of stable state.Disclosed alike closely in the United States Patent (USP) 4298444 that this structure and on November 3rd, 1981 publish by Chahroudi.In big vacuum chamber, rectangular chamber 36 is also referred to as " little " chamber.Main improvement is the single rectangle magnetron that bicylindrical shape rotating magnetron replaces prior art, and has improved the method that sputter gas injects.

Rectangle " little " chamber 36 is provided for the answer of use of RF sputter of the deposition of ZnS (or ZnSe) resilient coating from single planar magnetron, and is opposite with the rotating magnetron of explanation.This chamber forms the geometry homogeneous texture of isolating, and it provides uniform electrical environment for the RF sputter again.This permission is carried out the RF sputter equably along the length of magnetron.In addition, the protection chamber does not receive the pollution of other adjacent sputtering sources, so that only be made up of the ZnS material from the less back of the body sputter of locular wall.Thereby mix in the outside that protection ZnS n type layer is not caused by the pollutant by the outside.

Should be understood that the present invention is not limited to above-mentioned and in this illustrated example, but comprise any He all variations that fall into appended claim.For example, as obviously described in claim and specification, the accurate order execution that not every method step is all wanted following the instructions or required, but to allow to form any order of solar cell of the present invention.

Claims

1. method of making solar cell comprises:

Through carrying out sputter from first conductive targets and second conductive targets; Deposition p type semiconductor absorber layer; Wherein said p type semiconductor absorber layer comprises the alloy material based on two copper indium diselenide (CIS), makes that the p type semiconductor absorber layer of said deposition is that copper is not enough; Wherein

First target comprises the mixture of copper and selenium, or the mixture one of at least of copper, indium and aluminium plus gallium; And

Second target comprises the mixture one of at least of indium, selenium and aluminium plus gallium, or the mixture one of at least of copper, indium and aluminium plus gallium.

2. the method for claim 1, wherein:

First target comprises the mixture of copper and selenium; And

Second target comprises the mixture one of at least of indium, selenium and aluminium plus gallium.

3. method as claimed in claim 2, the mixture of wherein said copper and selenium comprise the copper of 30 atomic percents and the selenium of 70 atomic percents.

4. method as claimed in claim 2, the mixture one of at least of wherein said indium, selenium and aluminium plus gallium comprises the selenium that is less than 60 atomic percents.

5. method as claimed in claim 2 also comprises:

Between first target and second target, regulate power ratio, so that the p type semiconductor absorber layer that is deposited is the copper deficiency.

6. method as claimed in claim 2 is wherein depositing first conductive targets and deposition second conductive targets on second plane or cylindrical rotating magnetron on first plane or the cylindrical rotating magnetron.

7. method as claimed in claim 2, at least one in wherein said first conductive targets and said second conductive targets also comprises sodium.

8. the method for claim 1, wherein

First target comprises the mixture one of at least of copper, indium and aluminium plus gallium so that copper to the atomic ratio one of at least of indium and aluminium plus gallium less than one; And

Second target comprises the mixture one of at least of copper, indium and aluminium plus gallium so that copper to the atomic ratio one of at least of indium and aluminium plus gallium less than one.

9. method as claimed in claim 8, wherein

Alloy material based on CIS comprises two copper indium diselenide aluminum alloy materials, wherein copper to the atomic ratio of indium and aluminium less than one;

First target comprises the mixture of copper, indium and aluminium so that copper to the atomic ratio of indium and aluminium less than one; And

Second target comprises the mixture of copper, indium and aluminium so that copper to the atomic ratio of indium and aluminium less than one.

10. method as claimed in claim 8, wherein

Alloy material based on CIS comprises two copper indium gallium selenide (CIGS) alloy material, wherein copper to the atomic ratio of indium and gallium less than one;

First target comprises the mixture of copper, indium and gallium so that copper to the atomic ratio of indium and gallium less than one; And

Second target comprises the mixture of copper, indium and gallium so that copper to the atomic ratio of indium and gallium less than one.

11. method as claimed in claim 8 is wherein depositing first conductive targets and deposition second conductive targets on second plane or cylindrical rotating magnetron on first plane or the cylindrical rotating magnetron.

12. being included in, method as claimed in claim 11, the step that wherein deposits the p type semiconductor absorber layer contain in the selenium atmosphere reactively from first conductive targets and the second conductive targets sputter alloy material based on CIS.

13. method as claimed in claim 12, wherein sputter reactively comprises the alloy material of AC sputter based on CIS based on the step of the alloy material of CIS.

14. method as claimed in claim 12 wherein contains selenium atmosphere and comprises hydrogen selenide gas.

15. method as claimed in claim 8, at least one of wherein said first conductive targets and said second conductive targets also comprises sodium.

16. the method for claim 1 also comprises:

Through processing module a plurality of independent insulation, that connect web substrate is sent to output module from input module simultaneously, makes when transmitting, web substrate to be extended to output module from input module continuously through processing module a plurality of independent insulation, that connect;

Surface sputtering conductive membranes at substrate;

In the surface sputtering p of conductive membranes type semiconductor absorber layer;

In the surface sputtering n of p type semiconductor absorber layer type semiconductor layer to form p-n junction; With

The transparent conductivity of sputter top contact layer on the n type semiconductor layer;

Wherein each of conductive membranes, p type semiconductor absorber layer, n type semiconductor layer, transparent conductivity top contact layer is deposited on each the web substrate of processing module a plurality of independent insulation, that connect simultaneously.

17. a conduction sputtering target, it comprises the mixture one of at least of copper, indium and aluminium plus gallium so that copper to the atomic ratio one of at least of indium and aluminium plus gallium less than one.

18. method as claimed in claim 17, its mixture that hits by copper, indium and aluminium constitutes so that copper to the atomic ratio of indium and aluminium less than one.

19. method as claimed in claim 17, its mixture that hits by copper, indium and gallium constitutes so that copper to the atomic ratio of indium and gallium less than one.

20. method as claimed in claim 17, the wherein said target of deposition on plane or cylindrical rotating magnetron.

21. method as claimed in claim 17, wherein said target also comprises sodium.

22. method of making the conduction sputtering target; Said target comprises the mixture one of at least of copper, indium and aluminium plus gallium; This method comprises through pressed metal powder or casting and forms said target so that the copper in the said target to the atomic ratio one of at least of indium and aluminium plus gallium less than one.

23. method as claimed in claim 22, its mixture that hits by copper, indium and aluminium constitutes so that copper to the atomic ratio of indium and aluminium less than one.

24. method as claimed in claim 22, its mixture that hits by copper, indium and gallium constitutes so that copper to the atomic ratio of indium and gallium less than one.

25. method as claimed in claim 22 also is included in the said target of deposition on plane or the cylindrical rotating magnetron.

26. method as claimed in claim 22 wherein forms said target through pressed metal powder.

27. method as claimed in claim 22 wherein forms said target through casting.