A method for preparing a three-dimensional mixed halogen blue perovskite light-emitting diode device

Abstract

The present invention discloses a method for preparing a three-dimensional mixed halogen blue perovskite light emitting diode device, wherein cesium trifluoroacetate, lead bromide, lead chloride and cesium bromide are dissolved in dimethyl sulfoxide to prepare a mixed solution, and the solution is heated and stirred at not less than 60°C for at least 4 hours to obtain a three-dimensional mixed halogen perovskite precursor solution with a molar concentration of not less than 0.2M, and the solution is filtered and stored in a nitrogen environment for use; then, from bottom to top, a substrate is first used, and an ITO anode is arranged on the substrate; a hole transport layer, an interface modification layer, a perovskite light emitting layer, an electron transport layer, an electron injection layer and an electrode modification layer, and a cathode are sequentially arranged on the top of the ITO anode to obtain a three-dimensional mixed halogen blue perovskite light emitting diode device. The present invention introduces cesium trifluoroacetate, TFA, into the three-dimensional mixed halogen perovskite precursor solution. ‑ The C=O in the 2+ Combined with the inhibition of ion migration, the device has excellent spectral stability and good device performance.

Description

Technical Field

[0001] The present invention relates to the preparation of a blue light perovskite light emitting diode device, in particular to a preparation method of a mixed halogen blue light perovskite light emitting diode device with stable spectrum, and is applied to the technical field of new display device manufacturing. Background Art

[0002] Metal halide perovskite (MHP) has excellent optical and electrical properties such as high luminescence color purity, easy bandgap tuning, and high carrier mobility, and is an ideal luminescent layer material for light emitting diodes (LEDs).

[0003] In recent years, the development of perovskite light emitting diodes (PeLEDs) has been very rapid, and the stability and external quantum efficiency (EQE) of green and red PeLEDs have been greatly improved; the longest device lifetime can reach 115 min (@7200 cd m -2 ), the EQE has exceeded 20%, and the device performance can already be comparable to that of traditional OLEDs. However, the stability and EQE of blue light PeLEDs still lag far behind. The device lifetime is less than one percent of that of green and red PeLEDs, and the EQE is only about 10%, which severely limits the application of PeLEDs in the fields of full-color display and white light illumination.

[0004] The general structural formula of perovskite is ABX3 (X is a halogen anion Cl - , Br - , I - , A is a monovalent cation FA + , MA + , Cs + etc., B is a divalent cation Pb 2+ etc.), and by adjusting the mixing ratio of halogen ions (ABBr x Cl 3-x , 0 < x < 3), the spectrum can be adjusted from the green light band to the blue light band (410 - 490 nm), thereby realizing blue light emission. However, mixed halogen perovskite is prone to migration and aggregation of halogen ions under an external electric field, resulting in internal structural phase separation of perovskite, broadening and red-shifting of the spectrum, and deterioration of device performance, seriously affecting the spectral stability of the device. Therefore, designing and developing a method that can stabilize the emission spectrum of mixed halogen blue light PeLEDs is of great significance for improving the application prospects of PeLEDs. Summary of the Invention

[0005] In order to solve the problems of the prior art, the purpose of the present invention is to overcome the shortcomings of the existing technology and provide a method for preparing a three-dimensional mixed halogen blue light perovskite light-emitting diode device, which is a strategy for preparing a spectrally stable three-dimensional mixed halogen blue light perovskite light-emitting diode device, by introducing cesium trifluoroacetate (Cesium trifluoroacetate, CsTFA) into a three-dimensional mixed halogen perovskite precursor solution, TFA - The C=O in the 2+ Combined with the inhibition of ion migration, the device has excellent spectral stability and good device performance.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] A method for preparing a three-dimensional mixed halogen blue perovskite light-emitting diode device comprises the following steps:

[0008] a. Preparation of three-dimensional mixed-halogen perovskite precursors:

[0009] Dissolving cesium trifluoroacetate, lead bromide, lead chloride and cesium bromide in dimethyl sulfoxide to prepare a mixed solution, heating and stirring at not less than 60° C. for at least 4 hours to obtain a three-dimensional mixed halogen perovskite precursor solution with a molar concentration of not less than 0.2 M, filtering and storing in a nitrogen environment for use;

[0010] b. Preparation of three-dimensional mixed halogen perovskite light-emitting diode devices:

[0011] From bottom to top, the first step is to use a substrate, on which an ITO anode is arranged; a hole transport layer, an interface modification layer, a perovskite light-emitting layer, an electron transport layer, an electron injection layer, an electrode modification layer, and a cathode are arranged in sequence on the top of the ITO anode; a light-emitting unit is composed of the hole transport layer, the interface modification layer, the perovskite light-emitting layer, the electron transport layer, the electron injection layer, and the electrode modification layer; a three-dimensional mixed halogen blue perovskite light-emitting diode device is obtained.

[0012] Preferably, in the step a, a mixed solution is prepared according to a mixing ratio of dissolving 36.5 mg of cesium trifluoroacetate, 38.9 mg of lead bromide, 29.5 mg of lead chloride and 45.1 mg of cesium bromide in at least 1.5 mL of dimethyl sulfoxide.

[0013] Preferably, in the step b, the ITO film thickness of the ITO anode is 100-150 nm, and the sheet resistance is 15Ω / sq.

[0014] Preferably, in step b, the hole transport layer is nickel oxide (NiO x ) thin film, NiO x The film thickness is 35 to 40 nm.

[0015] Preferably, in step b, the interface modification layer is made of a sodium dodecyl sulfate film, and the thickness of the sodium dodecyl sulfate film is 3 to 5 nm.

[0016] Preferably, in step b, the perovskite light-emitting layer is made of a three-dimensional mixed halogen blue light perovskite CsPbClBr2 film, and the thickness of the CsPbClBr2 film is 35 to 40 nm.

[0017] Preferably, in the step b, the fluorescence quantum yield of the perovskite light-emitting layer is 15.3%, the emission wavelength is 482-484 nm, and the full width at half maximum (FWHM) is 22-24 nm.

[0018] Preferably, in the step b, the electron transport layer is made of a 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene thin film, and the thickness of the thin film is 30 to 35 nm.

[0019] Preferably, in step b, the electron injection layer / electrode modification layer is a lithium fluoride film, and the thickness of the lithium fluoride film is 1 nm.

[0020] Preferably, in step b, the cathode is an Al electrode, and the thickness of the cathode is not less than 100 nm.

[0021] Compared with the prior art, the present invention has the following obvious outstanding substantive features and significant advantages:

[0022] 1. The NiOx film in contact with the perovskite light-emitting layer contains a large number of defects such as oxygen vacancies, which will cause fluorescence quenching of the perovskite film, reduce the crystallinity of the perovskite crystal and the stability of the perovskite film; the interface modification layer SDS introduced in the present invention not only passivates the NiO x Surface defects inhibit the fluorescence quenching of the light-emitting layer and reduce the hole injection barrier, which is conducive to the effective injection of holes into the perovskite light-emitting layer, making the injection of holes and electrons more balanced, improving the external quantum efficiency of the three-dimensional mixed halogen blue light perovskite device, and improving the stability of the device;

[0023] 2. The present invention introduces CsTFA and TFA into the CsPbClBr2 perovskite precursor solution. - The C=O functional groups can effectively passivate the uncoordinated lead defects on the surface and grain boundaries of perovskite grains, eliminating the pathway for ion migration, thereby inhibiting ion migration under the action of an electric field and achieving stable EL emission (peak at 484nm) of blue PeLEDs at up to 10V.

[0024] 3. TFA of the present invention -The introduction of effectively improves the perovskite film morphology, reduces the grain size, and improves the crystallinity of the grains, which helps to inhibit the formation of defects and increase the probability of radiative recombination. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of a three-dimensional mixed halogen blue perovskite light-emitting diode device, where: 1-substrate, 2-ITO anode, 3-hole transport layer, 4-interface modification layer, 5-perovskite light-emitting layer, 6-electron transport layer, 7-electron injection layer / electrode modification layer, 8-cathode Al.

[0026] Figure 2 The electroluminescence spectra of three-dimensional mixed halogen blue perovskite light-emitting devices under different voltages.

[0027] Figure 3 This is the brightness-external quantum efficiency diagram of the three-dimensional mixed halogen blue light perovskite light-emitting device.

[0028] Figure 4 This is the voltage-brightness diagram of the three-dimensional mixed halogen blue light perovskite light-emitting device. DETAILED DESCRIPTION

[0029] The above scheme is further described below in conjunction with specific implementation examples. It should be noted that these embodiments are only used to illustrate the present invention and do not limit the scope of the present invention. After reading the content of the present invention, any modifications and substitutions made by those skilled in the art to the present invention fall within the scope defined by the claims attached to this application. The preferred embodiments of the present invention are described in detail as follows:

[0030] Example 1

[0031] In this embodiment, a method for preparing a three-dimensional mixed halogen blue perovskite light-emitting diode device comprises the following steps:

[0032] a. Preparation of three-dimensional mixed-halogen perovskite precursors:

[0033] A mixed solution was prepared by dissolving 36.5 mg of cesium trifluoroacetate, 38.9 mg of lead bromide, 29.5 mg of lead chloride and 45.1 mg of cesium bromide in 1.5 mL of dimethyl sulfoxide, and heated and stirred at 60° C. for 4 h to obtain a 0.2 M molar concentration three-dimensional mixed halogen perovskite precursor solution, which was filtered and stored in a nitrogen environment for use;

[0034] b. Preparation of three-dimensional mixed halogen perovskite light-emitting diode devices:

[0035] From bottom to top, a substrate 1 is first used, on which an ITO anode 2 is arranged; a hole transport layer 3, an interface modification layer 4, a perovskite light-emitting layer 5, an electron transport layer 6, an electron injection layer and an electrode modification layer 7, and a cathode 8 are arranged in sequence on the top of the ITO anode 2, and a light-emitting unit is formed by the hole transport layer 3, the interface modification layer 4, the perovskite light-emitting layer 5, the electron transport layer 6, the electron injection layer and the electrode modification layer 7; a three-dimensional mixed halogen blue perovskite light-emitting diode device is obtained, see Figure 1 , the steps for preparing a three-dimensional mixed halogen blue perovskite light-emitting device are as follows:

[0036] (1) Cleaning of the glass substrate containing the ITO transparent electrode, i.e., the anode: first, the ITO glass substrate was wiped with a dust-free cloth soaked in detergent, and then, it was continuously ultrasonically cleaned with deionized water, acetone, and isopropanol for 15 minutes each, and then the glass substrate was dried and its surface was treated with oxygen plasma gas for 15 minutes;

[0037] (2) Preparation of hole transport layer: Spin-coat 12 mg / ml NiO on ITO glass x Ethanol solution, the rotation speed is 8000r.pm, the spin coating time is 40s, and after the spin coating is completed, annealing is performed at 300℃ for 40min;

[0038] (3) Preparation of interface modification layer: On NiO x The film was spin-coated with a SDS solution dissolved in ethanol at a concentration of 5 mg / ml, a rotation speed of 4000 rpm, and a spin-coating time of 40 s. After the spin-coating was completed, the film was treated with oxygen plasma gas for 5 min.

[0039] (4) Preparation of perovskite light-emitting layer: After oxygen plasma treatment, a blue light perovskite solution is spin-coated, wherein the blue light perovskite is a three-dimensional mixed halogen CsPbClBr2 structure dissolved in dimethyl sulfoxide (DMSO) at a concentration of 0.2 mol / L, the rotation speed is 4000 rpm, the spin coating time is 40 s, and after the spin coating is completed, annealing is performed at 150°C for 2 min;

[0040] (5) Preparation of electron transport layer: The spin-coated device was transferred to a vacuum evaporation chamber and the vacuum degree was reduced to 10 -4 After Pa, TPBi was evaporated at a speed of 30-35nm thick;

[0041] (6) Preparation of electron injection layer / electrode modification layer: After the electron transport layer TPBi is evaporated, LiF was evaporated at a speed of 1 nm thick;

[0042] (7) Anode: Finally The Al electrode was evaporated at a speed of 100 nm in thickness.

[0043] Experimental test analysis

[0044] The electroluminescence spectrum of the three-dimensional blue light PeLEDs of Example 1 was characterized, and the electroluminescence spectrum of the three-dimensional blue light PeLEDs was obtained. Figure 2 As shown, the peak of its luminescence is located at 484nm, and the half-maximum width (FWHM) is 24nm, which is sky blue light. The narrower FWHM means higher color purity, and under the continuous action of bias voltage (5-10V), the spectrum does not shift, indicating that the introduction of CsTFA greatly inhibits the separation of halogens, thereby stabilizing the spectrum, which illustrates the role of CsTFA in stabilizing the spectrum in three-dimensional blue light PeLEDs.

[0045] The device performance test of the three-dimensional blue light PeLEDs of Example 1 was carried out, and the external quantum efficiency and brightness diagram of the three-dimensional blue light PeLEDs were obtained, as shown in FIG. Figure 3 and Figure 4 As shown. Due to the introduction of TFA - C=O in the ion is not conducive to the uncoordinated Pb in the perovskite 2+ This greatly suppresses non-radiative recombination, resulting in an EQE of 2.8% and a brightness of 3953 cdm -2 This shows that the three-dimensional blue light PeLEDs prepared based on this method have good device performance.

[0046] The invention technical solution of the three-dimensional mixed halogen PeLEDs modified by CsTFA in the above embodiment of the present invention introduces the interface modification layer SDS which not only passivates NiO x The surface defects inhibit the fluorescence quenching of the light-emitting layer and reduce the hole injection barrier, which is conducive to the effective injection of holes into the perovskite light-emitting layer, making the injection of holes and electrons more balanced, improving the external quantum efficiency of the three-dimensional mixed halogen blue light perovskite device, and improving the stability of the device. By introducing CsTFA, TFA into the CsPbClBr2 perovskite precursor solution - The C=O functional groups of the perovskite can effectively passivate the uncoordinated lead defects on the surface and grain boundaries of the perovskite grains, eliminating the pathway for ion migration, thereby inhibiting ion migration under the action of the electric field and achieving stable EL emission (peak at 484nm) of blue light PeLEDs at up to 10V. - The introduction of cesium trifluoroacetate (CsTFA) effectively improves the morphology of the perovskite film, reduces the grain size, and increases the crystallinity of the grains, which helps to inhibit the formation of defects and increase the probability of radiative recombination. -The C=O in the 2+ Combined with the inhibition of ion migration, the device has excellent spectral stability and good device performance.

[0047] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention of the present invention. Any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principle of the technical solution of the present invention should be equivalent replacement methods. As long as they meet the purpose of the invention of the present invention and do not deviate from the technical principles and inventive concepts of the present invention, they belong to the protection scope of the present invention.

Claims

1. A method for preparing a three-dimensional mixed halogen blue perovskite light-emitting diode device, characterized in that: The steps include: a. Preparation of three-dimensional mixed-halogen perovskite precursors: Dissolve cesium trifluoroacetate, lead bromide, lead chloride and cesium bromide in dimethyl sulfoxide to prepare a mixed solution, heat and stir at not less than 60°C for at least 4 hours to obtain a three-dimensional mixed halogen perovskite precursor solution with a molar concentration of not less than 0.2 M, filter and store in a nitrogen environment for use; b. Preparation of three-dimensional mixed halogen perovskite light-emitting diode devices: From bottom to top, a substrate (1) is first used, on which an ITO anode (2) is provided; a hole transport layer (3), an interface modification layer (4), a perovskite light-emitting layer (5), an electron transport layer (6), an electron injection layer and an electrode modification layer (7), and a cathode (8) are sequentially provided on the top of the ITO anode (2); a light-emitting unit is composed of the hole transport layer (3), the interface modification layer (4), the perovskite light-emitting layer (5), the electron transport layer (6), the electron injection layer and the electrode modification layer (7); and a three-dimensional mixed halogen blue perovskite light-emitting diode device is obtained.

2. The method for preparing the three-dimensional mixed halogen blue perovskite light-emitting diode device according to claim 1, characterized in that: In the step a, a mixed solution is prepared according to a mixing ratio of 36.5 mg of cesium trifluoroacetate, 38.9 mg of lead bromide, 29.5 mg of lead chloride and 45.1 mg of cesium bromide dissolved in at least 1.5 mL of dimethyl sulfoxide.

3. The method for preparing the three-dimensional mixed halogen blue perovskite light-emitting diode device according to claim 1, characterized in that: In the step b, the ITO film thickness of the ITO anode (2) is 100-150 nm, and the square resistance is 15 Ω / sq.

4. The method for preparing the three-dimensional mixed halogen blue perovskite light-emitting diode device according to claim 1, characterized in that: In step b, the hole transport layer (3) is nickel oxide (NiO x ) thin film, NiO x The film thickness is 35~40 nm.

5. The method for preparing the three-dimensional mixed halogen blue perovskite light-emitting diode device according to claim 1, characterized in that: In the step b, the interface modification layer (4) is made of a sodium dodecyl sulfate film, and the thickness of the sodium dodecyl sulfate film is 3-5 nm.

6. The method for preparing the three-dimensional mixed halogen blue perovskite light-emitting diode device according to claim 1, characterized in that: In the step b, the perovskite light-emitting layer (5) is made of a three-dimensional mixed halogen blue light perovskite CsPbClBr2 film, and the thickness of the CsPbClBr2 film is 35-40 nm.

7. The method for preparing the three-dimensional mixed halogen blue perovskite light-emitting diode device according to claim 1, characterized in that: In the step b, the fluorescence quantum yield of the perovskite light-emitting layer (5) is 15.3%, the emission wavelength is 482-484 nm, and the full width at half maximum (FWHM) is 22-24 nm.

8. The method for preparing the three-dimensional mixed halogen blue perovskite light-emitting diode device according to claim 1, characterized in that: In the step b, the electron transport layer (6) is made of a 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene thin film, and the thickness of the thin film is 30-35 nm.

9. The method for preparing the three-dimensional mixed halogen blue perovskite light-emitting diode device according to claim 1, characterized in that: In the step b, the electron injection layer / electrode modification layer (7) is a lithium fluoride film, and the thickness of the lithium fluoride film is 1 nm.

10. The method for preparing the three-dimensional mixed halogen blue perovskite light-emitting diode device according to claim 1, characterized in that: In the step b, the cathode (8) is an Al electrode, and the thickness of the cathode (8) is not less than 100 nm.

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