CN101000949B - Method for raising color purity of organic electroluminescence device wing photon crystal multi-layer film - Google Patents

Abstract

The method by using photonic crystal multi-layer to raise color purity of OLED is to use self-assembly technology to prepare a SiO2 nanosphere photonic crystal multi-layer in ITO layer of output roadfor OLED, and change photonic band position of the layer by choosing different diameter sizes of silica nanosphere, thus change the optical frequency range prohibited and allowed. Prohibiting shootingthe photons in the needless frequency range can improve the color purity of OLED. Comparing with the existing method of adding filters, using micro-cavity structure and preparing distributed Bragg reflector to improve the color purity, it is has simple process, lower cost, and reduces the waste of light energy for optical absorption and planar waveguide effect.

Description

Utilize photon crystal multi-layer film to improve the method for organic electroluminescence device color color purity

Technical field

The present invention relates to a kind of method that improves organic electroluminescence device color color purity, it will be applied to: 1) organic electroluminescence device.2) inorganic electroluminescence device of emission spectrum broad.

Background technology

In organic electroluminescence device, the emission spectrum broad of organic material commonly used, half-peak breadth is generally 50-100nm.Owing to the minimizing along with the half range value of luminescent spectrum of the visual sense efficient of human eye increases, the colorimetric purity that therefore improves organic electroluminescence device is very meaningful.In order to improve the colorimetric purity of display device, generally be to adopt the method for adding filter, unwanted light absorption is fallen, this has caused certain luminous energy waste; Another technology is to utilize micro-cavity structure, strengthens certain wavelengths by optimizing light emitting layer thickness, and this needs the accurately thickness of control luminescent layer, and also requires the thickness of red-green-blue luminescent layer to have nothing in common with each other in full-color display spare; Another technology is that the output at light prepares distributed Bragg reflector to select ejected wave long, and this needs expensive vacuum coating equipment, complex process, and cost is higher.

Summary of the invention

The technical problem to be solved in the present invention is to overcome luminous energy waste and the cost problem of higher that exists in the prior art, a method that improves organic electroluminescence device color color purity has been proposed, a photon crystal multi-layer film district is set in the ITO floor on output light path, with the emergent light reflected back luminescent layer in the certain frequency scope, and the light in the permission particular frequency range passes through, and has avoided the luminous energy waste that utilizes filter to bring like this when improving the emergent light colorimetric purity.Owing to the introducing of this thin layer, destroyed the Planar Optical Waveguide Structures of luminescent device simultaneously, reduced emergent light effectively because the luminous energy waste that the planar optical waveguide effect is brought.

Technical scheme of the present invention:

Utilize photon crystal multi-layer film to improve the step of the method for organic electroluminescence device color color purity:

Step 1 is utilized

The single SiO that disperses of method preparation ₂Nano microsphere requires relative standard deviation σ＜5% of microsphere diameter size; Following principle is followed in the selection of microsphere diameter size:

If requiring the centre wavelength of the certain frequency scope emergent light that no thoroughfare is λ ₀, then

$0.816D=\frac{{\mathrm{\λ}}_0}{2n_{\mathrm{eff}}}$

Wherein D is required SiO ₂Diameter of micro ball, effective refractive index n _Eff=1.347.

Above-mentioned

Method derives from document W, Fink A, Bohn E, J.Colloid interface Sci.26 (1968) 62. disclosed methods.

Step 2, the preparation of electroluminescent device anode: the glass that cleans up is dry in baking oven, prepare 8～50 layers SiO then at application self-assembling technique on glass ₂The microballoon photon crystal multi-layer film; The ITO layer of applying electronic beam evaporation or magnetron sputtering technique continued growth 50～200nm on photon crystal multi-layer film again;

Preparation SiO ₂In the time of the microballoon photon crystal multi-layer film, the number of plies is less than 8 layers can not provide tangible forbidden photon band, and the number of plies then can increase the preparation of devices difficulty more than 50 layers.

Above-mentioned self-assembling technique derives from document P.Jiang, J.F.Bertone, K.S.Hwang, V.L.Colvin, Chem.Mater, 11 (1999) 2132. disclosed methods

Step 3, the preparation of electroluminescent device luminescent layer and cathode electrode: application vacuum evaporation method or spin coating method prepare luminescent layer on the ITO layer, luminescent layer is an individual layer, or comprise the multilayer of luminescent layer, hole transmission layer and electron transfer layer, or comprise the only multilayer of one of luminescent layer, hole transmission layer and electron transfer layer; Evaporating Al electrode then.

The technique effect that the present invention compares with prior art:

In the prior art, the technology of improving organic electroluminescence device color color purity mainly contains: add colour filter, utilize micro-cavity structure or prepare distributed Bragg reflector at the output of light.The present invention compares with above-mentioned these technology, and cost is lower, and technology is simple relatively, has avoided the luminous energy that light absorption brought waste.Simultaneously, the introducing of photon crystal multi-layer film has destroyed the Planar Optical Waveguide Structures of luminescent device, reduces emergent light effectively because the optical energy loss that the planar optical waveguide effect is brought.

Principle of the present invention and foundation:

In photonic crystal, refractive index is periodically variable, and its cycle size is in the optical wavelength magnitude.When light is propagated in photonic crystal, owing to be subjected to the influence of periodically scattering, forbidden photon band can appear, frequency drops on photon in the forbidden photon band and will be reflected by photonic crystal and can not pass through.Utilize the SiO of self-assembling technique preparation ₂The Nano microsphere photon crystal multi-layer film can be regulated the position of forbidden photon band by the microballoon of selecting the different-diameter size, forbids and allows to pass through the light frequency scope thereby change.By forbidding that those are in the colorimetric purity that photon outgoing in the unwanted frequency scope just can improve organic electroluminescence device.

Description of drawings

Fig. 1 contains the organic electroluminescence device structural representation of photon crystal multi-layer film

1 is glass substrate among Fig. 1; 2 is the ITO layer; 3 is photon crystal multi-layer film; 4 is luminescent layer; 5 is metal electrode.

Fig. 2 luminescent material is ALq ₃The emission spectrum of simple organic electroluminescence device

Fig. 3 works as SiO ₂Photon crystal multi-layer film was＜111 when microsphere diameter was 285nm〉optical transmission property on the direction

Fig. 4 preparation has that luminescent material is ALq behind the photon crystal multi-layer film ₃The emission spectrum of organic electroluminescence device

Embodiment

Utilize photon crystal multi-layer film to improve the method for organic electroluminescence device color color purity:

ALq ₃Be a kind of green light material commonly used, but its emission spectrum is longer in the hangover of long wave direction, has influenced the colorimetric purity of luminescent device.

Step 1 is utilized Method prepares single SiO of dispersion of diameter D=285nm ₂Nano microsphere, the relative standard deviation σ of microsphere diameter size＜5%;

Step 2, the preparation of electroluminescent device anode: the glass that cleans up is dry in baking oven, then at the photon crystal multi-layer film of 16 layers of application self-assembling technique growths on glass; Use the ITO layer of magnetron sputtering technique continued growth 150nm on photon crystal multi-layer film again; Fig. 3 is that the photon crystal multi-layer film that calculates is＜111〉optical transmission property on the direction, with λ ₀=627nm is a centre wavelength, and the transmitance of the light in the width Delta λ ≈ 50nm scope is all less than 50%.

Step 3, the preparation of electroluminescent device luminescent layer and negative electrode: on the ITO layer, use vacuum evaporation method and prepare ALq ₃Luminescent layer, evaporating Al electrode then.To simple ALq ₃Emission spectrum of organic electroluminescence device (Fig. 2) and preparation have the ALq of photon crystal multi-layer film ₃The result of calculation of organic electroluminescence device emission spectrum (Fig. 4) shows, because with λ ₀=627nm is a centre wavelength, and the transmitance of the light in the width Delta λ ≈ 50nm scope is less than 50%, and the colorimetric purity of luminescent device has been brought up to 57.9%. from 54.8%

Claims (1)

1. utilize photon crystal multi-layer film to improve the method for organic electroluminescence device color color purity, it is characterized in that: use the anode that following step prepares organic electroluminescence device:

Step 1 is utilized

Method prepares dispersed nano SiO ₂Microballoon requires relative standard deviation σ＜5% of microsphere diameter size; Following principle is followed in the selection of microsphere diameter size:

If the centre wavelength of the emergent light of the certain frequency scope that no thoroughfare of requirement is λ ₀, then

$0.816D=\frac{{\mathrm{\λ}}_0}{2n_{\mathrm{eff}}}$

Wherein D is required SiO ₂Diameter of micro ball, effective refractive index n _Eff=1.347;

Step 2, the preparation of electroluminescent device anode: the glass that cleans up is dry in baking oven, then at the SiO of 8～50 layers of application self-assembling technique growths on glass ₂The microballoon photon crystal multi-layer film; The ITO layer of applying electronic beam evaporation or magnetron sputtering technique continued growth 50～200nm on photon crystal multi-layer film again.

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