CN116471859A - A kind of blue perovskite light-emitting diode and its preparation method - Google Patents

Abstract

The invention discloses a blue perovskite light-emitting diode and a preparation method thereof; the blue perovskite light-emitting diode includes a light-emitting layer, and the light-emitting layer is a perovskite light-emitting layer spin-coated with an organic solution of tetrabutylammonium chloride. The invention obtains the light-emitting layer by spin-coating the organic solution of tetrabutylammonium chloride on the perovskite light-emitting layer. The perovskite light-emitting layer after spin-coating tetrabutylammonium chloride in the invention can well realize blue light emission, and solves the problem that inorganic chlorine is insoluble in precursors in halogen engineering. At the same time, the dynamic spin-coating material used is tetrabutylammonium chloride, which is an ionic compound. It dissolves in chlorobenzene and ionizes chloride ions without excessive hydrolysis reaction, and efficiently realizes the spectral transition from green to blue near 50nm. In addition, the addition of tetrabutylammonium chloride can passivate defects, which is beneficial to obtain a high-quality perovskite light-emitting layer.

Description

A kind of blue perovskite light-emitting diode and its preparation method

technical field

The invention belongs to the technical field of photoelectric devices, and in particular relates to a blue perovskite light-emitting diode and a preparation method thereof.

Background technique

Metal halide perovskite materials have become strong candidates for the preparation of high-efficiency optoelectronic devices due to their excellent properties such as low-temperature solution processing, high carrier mobility, tunable optical bandgap, large carrier diffusion length, and high color purity. Its development is also very rapid. In a short period of time, its efficiency has been greatly improved. At present, the efficiency of green and red PeLEDs has exceeded 20%. However, the development of blue perovskite light-emitting diodes is relatively lagging behind, especially in deep blue PeLEDs. At present, there are two main ways to achieve deep blue light emission, namely space engineering and halogen engineering. Among them, space engineering uses the quantum confinement effect to adjust the band gap of perovskite and achieve blue shift by doping with organic ligands. However, realizing deep blue light requires more organic ligands, which will lead to serious non-radiative recombination and aggravate the problem of charge injection. In halogen engineering, it is necessary to add chloride ions to the precursor to adjust the band gap to blue shift, but the low solubility of inorganic chloride salts in DMSO/DMF limits the possibility of component regulation, and chloride ions will lead to higher defect state density (Nenon DP, Pressler K, KangJ, et al. Design principles for trap-free CsPbX3 nanocrystals: enumerating and eliminating surface hal ide vacancies with softer Lewis bases [J]. Journal of the American Chemical Society, 2018, 140(50): 17760-17772.). Therefore, in order to synchronize the overall development of tricolor PeLEDs, it is urgent to solve the problems of blue PeLEDs preparation and efficiency improvement.

Contents of the invention

In order to solve the above problems, the object of the present invention is to provide a blue perovskite light-emitting diode and a preparation method thereof. In this method, chlorine-containing quaternary ammonium salt is dynamically spin-coated and post-treated, and chlorine ions are efficiently and quickly incorporated to realize ion exchange without redundant hydrolysis reaction, and the light color transition from green light to blue light near 50nm is realized; at the same time, the luminous efficiency is improved.

Above-mentioned purpose of the present invention is realized through following technical scheme:

A blue perovskite light-emitting diode, comprising a light-emitting layer, the light-emitting layer is a perovskite light-emitting layer spin-coated with an organic solution of tetrabutylammonium chloride.

Preferably, the perovskite light-emitting layer is composed of phenethylammonium bromide, cesium bromide and lead bromide in a molar ratio of 0.2-0.6:1.0-1.2:1; the thickness of the perovskite light-emitting layer is 10-20 nm.

Further preferably, the perovskite light-emitting layer is composed of phenethylammonium bromide, cesium bromide and lead bromide with a molar ratio of 0.4:1:1;

Preferably, the perovskite light-emitting layer is formed by spin-coating a perovskite precursor solution; wherein the perovskite precursor solution is prepared from PEABr, CsBr and _PbBr2 , the spin-coating speed is 3000-6000rpm/min, the spin-coating time is 30-60s, and annealed at 60-90°C for 1-10min under a protective atmosphere after spin-coating.

Preferably, the organic solvent in the organic solution of tetrabutylammonium chloride is chlorobenzene;

Preferably, the concentration of the organic solution of tetrabutylammonium chloride is 1-4 mg/mL.

Preferably, the spin coating is dynamic spin coating; the speed of the spin coating is 4000-7000rpm/min; the time of the spin coating is 30-60s; the thickness of the spin coating is 1-3nm.

Preferably, the blue perovskite light emitting diode is formed by stacking an anode, a hole injection layer, a light emitting layer, an electron transport layer, an electron injection layer and a cathode from bottom to top.

Further preferably, the anode is at least one of metal, metal oxide, graphene and its derivatives; the processing method of the anode includes sputtering, chemical vapor deposition, and spray pyrolysis.

More preferably, the metal oxide includes indium tin oxide conductive film, doped tin dioxide zinc oxide, indium gallium zinc oxide.

Further preferably, the hole injection layer is PEDOT:PSS:Arg;

Further preferably, the hole injection layer is formed by a solution spin-coating process; wherein, the spin-coating speed is 2000-4000rpm/min, the spin-coating time is 20-40s, and annealed at 150-180°C for 5-15min in an atmospheric environment after spin-coating.

Further preferably, the electron transport layer is TPBi, and the electron injection layer is LiF;

Further preferably, the cathode is metal, metal alloy or metal oxide; the processing method of the cathode includes electrode evaporation, solution processing, and inkjet printing.

In the above preparation method of the blue perovskite light-emitting diode, an organic solution of tetrabutylammonium chloride is spin-coated on the perovskite light-emitting layer to obtain the light-emitting layer.

Compared with the prior art, the beneficial effects of the present invention are:

In the present invention, the tetrabutylammonium chloride solution is dynamically spin-coated on the perovskite light-emitting layer, and chloride ions are mixed into the green light perovskite light-emitting layer through an interface ion exchange method to adjust the band gap and achieve the blue shift of light color, thereby realizing the blue perovskite light-emitting diode. The optimized perovskite light-emitting layer can achieve blue light emission well, which solves the problem that inorganic chlorine is insoluble in the precursor in halogen engineering. At the same time, the dynamic spin-coating material used is tetrabutylammonium chloride, which is an ionic compound, which dissolves in chlorobenzene and ionizes chloride ions without excessive hydrolysis reactions, and efficiently realizes the spectral transition from green to blue near 50nm. In addition, the addition of tetrabutylammonium chloride can passivate defects, which is conducive to obtaining a high-quality perovskite light-emitting layer and improving luminous efficiency. In a word, the process method provided by the present invention is simple, has good repeatability, is easy to operate, has a wide source of materials and is cheap, and provides a feasible idea for the future production of blue perovskite light-emitting diodes.

Description of drawings

Fig. 1 is process schematic diagram of the present invention;

Fig. 2 is a schematic view of the device structure of the present invention;

Fig. 3 is the perovskite light-emitting diode J-V-L curve prepared by embodiment 1-3 and comparative example;

Fig. 4 is the perovskite light-emitting diode J-EQE curve prepared by embodiment 1-3 and comparative example;

Fig. 5 is a normalized PL spectrum diagram of perovskite light-emitting diodes prepared in Examples 1-3 and Comparative Examples.

Detailed ways

The embodiments of the present invention will be described in detail below. Based on the technical solution of the present invention, this embodiment provides detailed implementation and specific operation process. The protection scope of the present invention includes but not limited to the following examples.

A method for preparing blue perovskite light-emitting diodes by dynamic spin coating of tetrabutylammonium chloride provided by the invention comprises the following steps:

(1) cleaning the anode base;

(2) preparing a hole injection layer;

Dropping the hole injection solution on the upper anode substrate, annealing after spin coating;

(3) Preparation of perovskite light-emitting layer

Dropping the perovskite solution on the hole injection layer film, annealing after spin-coating; treating the solution on the perovskite light-emitting layer after dynamic spin-coating;

(4) Preparation of electron transport layer

Under high vacuum, evaporate TPBi above the perovskite light-emitting layer to obtain an electron transport layer;

(5) Preparation of electron injection layer

Under high vacuum, the electron injection layer is deposited by thermal evaporation on the electron transport layer;

(6) Preparation of cathode

A cathode with a certain thickness is evaporated on the electron injection layer.

Further, the anode substrate in the step (1) is one of ITO substrate, IZO substrate or FTO substrate. Preferably, the anode substrate is sequentially washed in tetrahydrofuran, isopropanol, lotion, and deionized water, and then ultrasonically cleaned in isopropanol. The ultrasonic time is 10-20 minutes each time; after the ultrasonic wave is completed, the substrate is dried in an oven for more than 2 hours, and then the substrate is treated with UV or O ₂ -Plasma for 10-15 minutes.

Further, the preparation method of the hole injection layer in the step (2) is: adding 2-6 mg/ml arginine (Arg) aqueous solution into the hole injection layer polymer solution PEDOT:PSS, filtering the doped solution through a 0.22 μm water-based filter head and adding it dropwise on the anode substrate to form a hole injection layer film by spin coating. The spin coating speed is 2000-4000 rpm/min, and the spin coating time is 20-40 seconds. Anneal at -180°C for 5-15 minutes. Preferably, the spin coating speed is 3000 rpm/min, the dosage is 100 ul, the spin coating time is 30 s, the annealing is at 160° C. for 10 min, and the Arg solution concentration is 4 mg/ml.

Further, the perovskite solution in the step (3) is prepared from PEABr, CsBr and _PbBr , wherein the _molar ratio of PEABr:CsBr:PbBr is (0.2～0.6):(1～1.2):1, preferably the molar ratio is 0.4:1:1. The total content of solutes PEABr, CsBr and PbBr ₂ is 5-20 wt.%, preferably 10 wt.%. The solvent can be anhydrous N,N-dimethylformamide (DMF) or dimethyl sulfoxide (DMSO), preferably DMSO.

The perovskite solution spin coating speed is 3000-6000rpm/min, and the preferred spin coating speed is

5000rpm/min. The spin coating time is 30-60s, and the preferred spin coating time is 60s. Then anneal at 70-100° C. for 5-15 min in a nitrogen environment in a glove box. The preferred annealing temperature is 70°C and the annealing time is 5min. Preferably, the dosage of the perovskite solution is 55uL.

The dynamic spin-coating solution is a tetrabutylammonium chloride solution with a molar concentration of 1-4 mg/mL, preferably 3.5 mg/mL. The solvent is isopropanol or chlorobenzene, preferably chlorobenzene.

The spin-coating speed of the dynamic spin-coating solution is 4000-6000 rpm/min, and the preferred spin-coating speed is 6000 rpm/min. The spin-coating time is 30-60min, and the preferred spin-coating time is 60s. Preferably, the amount of the dynamic spin coating solution is 55 μL.

Further, the steps (4), (5), and (6) all need to transfer the device into a vacuum evaporation chamber for electron transport layer, electron injection layer and cathode evaporation. The thickness of the evaporated electron transport layer is 30-40nm, preferably 40nm. The thickness of the evaporated electron injection layer is 0.5-1 nm, preferably 1 nm. The thickness of the evaporated cathode is 100-150 nm, preferably 100 nm.

A blue perovskite light-emitting diode prepared by tetrabutylammonium chloride dynamic spin coating, the light-emitting device sequentially includes a substrate, an anode electrode layer, a hole injection layer, a perovskite light-emitting layer, an electron transport layer, an electron injection layer and a metal cathode from bottom to top. Wherein, in the step of forming the perovskite light-emitting layer of the device, a tetrabutylammonium chloride solution is dynamically spin-coated on the perovskite light-emitting layer to obtain an optimized perovskite light-emitting layer.

Example 1

The device structure of the present embodiment is: anode (ITO)/hole injection layer (PEDOT:PSS:Arg)/blue light perovskite light-emitting layer/electron transport layer (TPBi)/electron injection layer (LiF)/cathode (Al) whose emission spectrum peak wavelength is 485nm, as shown in Figure 2.

The preparation process is as follows (refer to Figure 1):

a. Place the ITO substrate used in tetrahydrofuran, isopropanol, micron-scale semiconductor special cleaning solution (a mixed solution of ZT-3 electronic cleaning solution and deionized water with a volume ratio of 1:100), deionized water, and isopropanol for ultrasonic cleaning, and the ultrasonic cleaning time is 15 minutes each time. After the ultrasound is completed, place the ITO substrate in an oven to dry for more than 2 hours for later use.

b. Preparation solution:

1) Preparation of hole injection layer solution: Take out PEDOT:PSS aqueous solution with a mass fraction of 1.5% from a refrigerator at 4°C, and let it stand for half an hour until the solution returns to room temperature. A hole injection layer solution was obtained by mixing 4 mg/ml Arg aqueous solution and PEDOT:PSS aqueous solution at a volume ratio of 1:2.

2) Preparation of perovskite precursor solution: configure 10wt.% PEABr, FABr and PbBr ₂ solutions respectively (the solvent is DMSO), and then mix PEABr, CsBr and PbBr ₂ solutions in a molar ratio of 0.4:1:1 to obtain a perovskite precursor solution.

c. Before the hole injection layer is spin-coated, the ITO substrate used is subjected to UV treatment for 10 minutes to improve the wettability on the ITO. Filter the hole injection layer solution through a 0.22 μm water-based filter head and drop it on the ITO substrate. Spin coating at a speed of 3000 rpm/min for 30 s by spin coating, and then anneal in air at 150 ° C for 10 min. The thickness of the hole injection layer is 10 nm;

d. According to the lamination sequence of the device structure, the substrate is passed into the glove box to spin-coat the perovskite layer. The amount of spin-coating is 55 μL, the spin-coating speed is 5000rpm/min, and the spin-coating time is 60s. Then, heat treatment is carried out. The temperature is 70°C, heated for 5min, and the thickness of the perovskite light-emitting layer is 15nm; The coating speed is 6000rpm/min, and the spin coating time is 60s.

e. After spin-coating all functional layers, transfer the device into a vacuum evaporation chamber for electron transport layer, electron injection layer and cathode evaporation. The thickness of the evaporated electron transport layer is 40nm, the thickness of the evaporated electron injection layer is 1nm, and the thickness of the evaporated cathode is 100nm;

f. After the aluminum electrodes are evaporated, the device is packaged with epoxy resin and a glass cover, and the electrical properties (electrical properties such as current, voltage, brightness, efficiency and color coordinates of the device) are characterized outside the glove box.

Example 2

The device structure of the present embodiment is: anode (ITO)/hole injection layer (PEDOT:PSS:Arg)/blue light perovskite light-emitting layer/electron transport layer (TPBi)/electron injection layer (LiF)/cathode (Al) whose emission spectrum peak wavelength is 475nm, as shown in Figure 2.

The preparation process is as follows:

a. Place the ITO substrate used in tetrahydrofuran, isopropanol, micron-scale semiconductor special cleaning solution (a mixed solution of ZT-3 electronic cleaning solution and deionized water with a volume ratio of 1:100), deionized water, and isopropanol for ultrasonic cleaning, and the ultrasonic cleaning time is 15 minutes each time. After the ultrasound is completed, place the ITO substrate in an oven to dry for more than 2 hours for later use.

b. Preparation solution:

1) Preparation of hole injection layer solution: Take out PEDOT:PSS aqueous solution with a mass fraction of 1.5% from a refrigerator at 4°C, and let it stand for half an hour until the solution returns to room temperature. A hole injection layer solution was obtained by mixing 4 mg/ml Arg aqueous solution and PEDOT:PSS aqueous solution at a volume ratio of 1:2.

2) Preparation of perovskite precursor solution: respectively configure 10wt.% PEABr, FABr and PbBr2 solutions (solvent is DMSO), and then mix PEABr, CsBr and PbBr2 solutions at a molar ratio of 0.4:1:1 to obtain a perovskite precursor solution.

c. Before the hole injection layer is spin-coated, the ITO substrate used is subjected to UV treatment for 10 minutes to improve the wettability on the ITO. Filter the hole injection layer solution through a 0.22 μm water-based filter head and drop it on the ITO substrate. Spin coating at a speed of 3000 rpm/min for 30 s by spin coating, and then anneal in air at 150 ° C for 10 min. The thickness of the hole injection layer is 10 nm;

d. According to the lamination sequence of the device structure, the substrate is passed into the glove box to spin-coat the perovskite layer. The amount of spin-coating is 55 μL, the spin-coating speed is 5000rpm/min, and the spin-coating time is 60s. Then, heat treatment is carried out. The temperature is 70°C, heated for 5min, and the thickness of the perovskite light-emitting layer is 15nm; The coating speed is 6000rpm/min, and the spin coating time is 60s.

e. After spin-coating all functional layers, transfer the device into a vacuum evaporation chamber for electron transport layer, electron injection layer and cathode evaporation. The thickness of the evaporated electron transport layer is 40nm, the thickness of the evaporated electron injection layer is 1nm, and the thickness of the evaporated cathode is 100nm;

f. After the aluminum electrodes are evaporated, the device is packaged with epoxy resin and a glass cover, and the electrical properties (electrical properties such as current, voltage, brightness, efficiency and color coordinates of the device) are characterized outside the glove box.

Example 3

The device structure of the present embodiment is: anode (ITO)/hole injection layer (PEDOT:PSS:Arg)/deep blue light perovskite light-emitting layer/electron transport layer (TPBi)/electron injection layer (LiF)/cathode (Al) with emission spectrum peak wavelength of 465nm, as shown in Figure 2.

The preparation process is as follows:

a. Place the ITO substrate used in tetrahydrofuran, isopropanol, micron-scale semiconductor special cleaning solution (a mixed solution of ZT-3 electronic cleaning solution and deionized water with a volume ratio of 1:100), deionized water, and isopropanol for ultrasonic cleaning, and the ultrasonic cleaning time is 15 minutes each time. After the ultrasound is completed, place the ITO substrate in an oven to dry for more than 2 hours for later use.

b. Preparation solution:

1) Preparation of hole injection layer solution: Take out PEDOT:PSS aqueous solution with a mass fraction of 1.5% from a refrigerator at 4°C, and let it stand for half an hour until the solution returns to room temperature. A hole injection layer solution was obtained by mixing 4 mg/ml Arg aqueous solution and PEDOT:PSS aqueous solution at a volume ratio of 1:2.

2) Preparation of perovskite precursor solution: respectively configure 10wt.% PEABr, FABr and PbBr2 solutions (solvent is DMSO), and then mix PEABr, CsBr and PbBr2 solutions at a molar ratio of 0.4:1:1 to obtain a perovskite precursor solution.

c. Before the hole injection layer is spin-coated, the ITO substrate used is subjected to UV treatment for 10 minutes to improve the wettability on the ITO. Filter the hole injection layer solution through a 0.22 μm water-based filter head and drop it on the ITO substrate. Spin coating at a speed of 3000 rpm/min for 30 s by spin coating, and then anneal in air at 150 ° C for 10 min. The thickness of the hole injection layer is 10 nm;

d. According to the lamination sequence of the device structure, the substrate is passed into the glove box to spin-coat the perovskite layer. The amount of spin-coating is 55 μL, the spin-coating speed is 5000rpm/min, and the spin-coating time is 60s. Then, heat treatment is carried out. The temperature is 70°C, heated for 5min, and the thickness of the perovskite light-emitting layer is 15nm; The coating speed is 6000rpm/min, and the spin coating time is 60s.

e. After spin-coating all functional layers, transfer the device into a vacuum evaporation chamber for electron transport layer, electron injection layer and cathode evaporation. The thickness of the evaporated electron transport layer is 40nm, the thickness of the evaporated electron injection layer is 1nm, and the thickness of the evaporated cathode is 100nm;

f. After the aluminum electrodes are evaporated, the device is packaged with epoxy resin and a glass cover, and the electrical properties (electrical properties such as current, voltage, brightness, efficiency and color coordinates of the device) are characterized outside the glove box.

comparative example

In this comparative example, only the perovskite light-emitting layer in step c is different from the embodiment. In this case, the post-treatment solution of tetrabutylammonium chloride is not dynamically spin-coated, and the annealed perovskite film is directly used as the light-emitting layer. The remaining steps are the same as in Embodiment 1, and will not be repeated here.

Performance Testing:

1) The electrical properties such as current density, voltage, brightness, EQE and color coordinates of the perovskite light-emitting diodes of Examples 1 to 3 and comparative examples are tested, and the obtained J-V-L curve is shown in Figure 3, and the J-EQE curve is shown in Figure 4.

It can be seen from Figure 3 that after the perovskite film is treated by TBAC dynamic spin coating, the current density and brightness decrease with the increase of TBAC concentration, which is because the doping of chloride ions will affect the injection and transport of carriers.

It can be seen from Figure 4 that after the perovskite film is treated by TBAC dynamic spin coating, as the concentration of TBAC increases, the EQE first increases and then decreases. This is because a small amount of TBAC can passivate defects very well, inhibit non-radiative recombination, and improve device performance, but when more chloride ions are doped, the performance drops significantly due to the low defect tolerance of chlorine.

3) The normalized PL spectrum of perovskite light-emitting diodes after TBAC dynamic spin-coating treatment is shown in Figure 5.

It can be seen from Figure 5 that after TBAC dynamic spin-coating treatment, the perovskite thin film can realize luminescence in different bands from sky blue light to deep blue light.

It can be understood that, the above embodiments are only exemplary embodiments adopted for illustrating the principle of the present invention, but the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also regarded as the protection scope of the present invention.

Claims (10)

1. A blue perovskite light-emitting diode, characterized in that it comprises a light-emitting layer, and the light-emitting layer is a perovskite light-emitting layer of an organic solution of spin-coated tetrabutylammonium chloride. 2. The blue perovskite light-emitting diode according to claim 1, wherein the perovskite light-emitting layer is composed of phenethylammonium bromide, cesium bromide and lead bromide with a molar ratio of 0.2～0.6:1.0～1.2:1; the thickness of the perovskite light-emitting layer is 10-20nm; The perovskite luminescent layer is formed by spin-coating a perovskite precursor solution; wherein the perovskite precursor solution is prepared from PEABr, CsBr and _PbBr2 , the spin-coating speed is 3000-6000rpm/min, the spin-coating time is 30-60s, and annealed at 60-90°C for 1-10min under a protective atmosphere after spin-coating. 3. blue perovskite light-emitting diode according to claim 1, is characterized in that, the organic solvent in the organic solution of described tetrabutyl ammonium chloride is chlorobenzene; The concentration of the organic solution of tetrabutylammonium chloride is 1-4 mg/mL. 4. The blue perovskite light-emitting diode according to claim 1, wherein the spin coating is dynamic spin coating; the speed of the spin coating is 4000-7000rpm/min; the time of the spin coating is 30-60s; the thickness of the spin coating is 1-3nm. 5 . The blue perovskite light-emitting diode according to claim 1 , wherein the blue perovskite light-emitting diode is formed by stacking an anode, a hole injection layer, a light-emitting layer, an electron transport layer, an electron injection layer and a cathode from bottom to top. 6. The blue perovskite light-emitting diode according to claim 5, wherein the anode is at least one of metal, metal oxide, graphene and its derivatives; the processing method of the anode includes sputtering, chemical vapor deposition, and spray pyrolysis. 7 . The blue perovskite light-emitting diode according to claim 6 , wherein the metal oxide comprises indium tin oxide conductive film, tin dioxide-doped zinc oxide, and indium gallium zinc oxide. 8. The blue perovskite light-emitting diode according to claim 5, wherein the hole injection layer is PEDOT:PSS:Arg; The hole injection layer is formed by a solution spin-coating process; wherein, the spin-coating speed is 2000-4000rpm/min, the spin-coating time is 20-40s, and annealed at 150-180°C for 5-15min in an atmospheric environment after spin-coating. 9. The blue perovskite light-emitting diode according to claim 5, wherein the electron transport layer is TPBi, and the electron injection layer is LiF; The cathode is metal, metal alloy or metal oxide; the processing method of the cathode includes electrode evaporation, solution processing, and inkjet printing. 10. The preparation method of the blue perovskite light-emitting diode according to any one of claims 1-9, characterized in that an organic solution of tetrabutylammonium chloride is spin-coated on the perovskite light-emitting layer to obtain the light-emitting layer.