Blue perovskite light-emitting diode based on ammonium bromide and preparation method thereof

Abstract

The invention discloses a blue perovskite light-emitting diode based on ammonium bromide and a preparation method thereof, and belongs to the field of perovskite light-emitting materials and devices, the blue perovskite light-emitting diode comprises an electrode, a carrier transport layer and a light-emitting layer, and the light-emitting layer is quasi-two-dimensional A6BfP2 (RbxCs1-x) 2Pb3Br10 perovskite obtained by creatively adding a novel additive, due to the quasi-two-dimensional A6BfP2 (RbxCs1-x) 2Pb3Br10 perovskite layer, the light-emitting wavelength of the perovskite light-emitting device is about 476 nm, and the highest EQE is 11.9%.

Description

Technical Field

[0001] The invention belongs to the field of perovskite light-emitting materials and devices, and in particular relates to a blue perovskite light-emitting diode based on ammonium bromide salt and a preparation method thereof. Background Art

[0002] Metal halide perovskites (MHPs) are a promising new type of semiconductor material with the characteristics of low cost, spectral tunability and high photoluminescence quantum yields (PLQYs), which have broadened optoelectronic application scenarios. At present, the highest external quantum efficiency (EQE) of green perovskite LEDs (PeLEDs) and red PeLEDs exceeds 28%, which is comparable to traditional OLEDs and QLEDs. However, LEDs emitting in the blue band at around 470nm still lag behind green and red PeLEDs. Low color purity, moderate external efficiency and poor device lifetime are serious obstacles to the commercialization of perovskite light-emitting diodes. Therefore, when promoting the commercial development of PeLEDs, issues such as full width at half maximum (FWHM), reducing efficiency roll-off, and extending the service life of the device should be considered.

[0003] Generally speaking, there are two approaches to obtain blue PeLEDs. The first approach is to tune the band gap by adding chlorine to bromine-based perovskites. However, these mixed-halide perovskites exhibit intrinsic phase instabilities, especially under potential, which is caused by halide migration. As a result, the electroluminescence (EL) spontaneously shifts from blue to green within a few minutes of device operation. Almost all PeLEDs based on the mixed-halide strategy exhibit rapid electroluminescence decay. Adjusting the quantum well structure to achieve reduced-dimensional (quasi-two-dimensional) perovskites is another effective approach to produce blue PeLEDs, and blue light emission can be achieved by keeping the quantum well structure in an extremely low thickness region (n≤2).

[0004] Previously, blue PeLED devices suffered from poor performance and low spectral stability, and a practical remedy was urgently needed. Summary of the invention

[0005] The problem to be solved by the present invention is: how to provide a blue perovskite light-emitting diode based on ammonium bromide salt and a preparation method thereof, so that its electroluminescence (EL) spectrum band is within the blue light range and has better wavelength stability.

[0006] To solve the above problems, the present invention provides the following technical solutions: A blue perovskite light-emitting diode based on ammonium bromide salt comprises a substrate with an ITO anode printed thereon, a PEDOT:PSS hole transport layer, a PVK hole transport layer, a perovskite light-emitting layer, a TPBi electron transport layer, a LiF electron transport layer and an Al cathode, which are sequentially connected from one side to the other.

[0007] A method for preparing a blue perovskite light-emitting diode based on ammonium bromide salt comprises the following steps: S1: Place the substrate printed with ITO anode into a mixed solution of anhydrous ethanol and deionized water, and ultrasonicate it for 20 minutes, then blow dry the liquid on its surface with nitrogen; S2: Place the substrate printed with ITO anode into UV cleaning agent and clean it with UV ozone for 15 minutes; S3: Spin-coat a PEDOT:PSS film on a substrate printed with an ITO anode using a coater and heat it on a hot plate for 15 minutes to generate a PEDOT:PSS hole transport layer on the substrate with the ITO anode; S4: Place the substrate printed with the ITO anode in a nitrogen-filled glove box, spin-coat the PVK film, and heat it on a hot plate for 20 minutes to generate a PVK hole transport layer on the PEDOT:PSS hole transport layer; S5: After the PVK film is cooled, the perovskite precursor solution is spin-coated on the PVK hole transport layer at a rotation speed of 4000 rpm, and heated at 100° C. for 10 minutes to generate a perovskite light-emitting layer on the PVK hole transport layer; S6: Finally, the substrate printed with ITO anode is placed in the evaporation equipment and vacuumed. When the pressure is less than 4×10 -4 TPBi, LiF and Al thin films were sequentially evaporated at pa with thicknesses of 80nm, 1nm and 100nm, respectively.

[0008] Preferably, in S5, the preparation method of the perovskite precursor solution is: PbBr2, CsBr, RbBr and A6BfPBr are placed in a glass bottle and DMSO is added to obtain a configuration solution, and the configuration solution is placed on a stirring table and stirred at room temperature for 12 hours to obtain a perovskite precursor solution.

[0009] Preferably, the concentration of PbBr2 in the perovskite precursor solution is 73.4 mg / ml.

[0010] Preferably, the concentration of CsBr in the perovskite precursor solution is 0-42.56 mg / ml.

[0011] Preferably, the concentration of RbBr in the perovskite precursor solution is 0-33.07 mg / ml.

[0012] Preferably, the chemical formula of A6BfPBr is: 18 H 21 BrN2O2, chemical structure formula is: .

[0013] Compared with the existing material synthesis method, the present invention has the following advantages: 1. The blue perovskite light-emitting diode obtained by using long-chain ammonium salt N-aminohexylbenzo[e]-phthalimide hydrobromide (A6BfPBr) as an additive in this application inhibits cation diffusion, while maximizing the passivation effect and creating a more solid octahedral network. In addition, the long organic chain ammonium salt and large group separation distance create opportunities for the pairing of passivated ammonia with perovskite defect sites. Thereby improving the spectral stability of the material; 2. This application adds different proportions of rubidium (Rb) to the perovskite precursor, because Rb (Rb + , 152 pm) has a smaller ionic radius than cesium (Cs + , 167pm). Therefore, Rb + Incorporation of three-dimensional CsPbBr3 perovskite is expected to produce alloyed perovskite Rb x Cs 1-x PbBr3, this perovskite has a larger band gap due to octahedral titration. Rb x Cs 1-x PbBr3 (0≤x≤1) perovskite is prepared by solution process. + The increase in Rb content x Cs 1-x The optical band gap of PbBr3 film increases from 2.31eV to 2.60eV. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of the light emitting diode device involved in the present invention; The markings in the figure are: 1-substrate printed with ITO anode; 2-PEDOT:PSS hole transport layer; 3-PVK hole transport layer; 4-perovskite light-emitting layer; 5-TPBi electron transport layer; 6-LiF electron transport layer; 7-Al cathode. DETAILED DESCRIPTION

[0015] In order to facilitate those skilled in the art to understand the technical content of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific examples. It should be understood that the specific examples described herein are only used to explain the present invention and are not used to limit the present invention.

[0016] The concentration unit mM used in this application is an abbreviation for millimole per liter.

[0017] Example 1 (control group) (1) Preparation of perovskite precursor solution: Prepare two glass bottles with a volume of 4 ml, wash them with deionized water and ethanol, blow dry them, and put in a clean magnet. Put 73.4 mg PbBr2, 17 mg CsBr, 19.84 mg RbBr and 40.4 mg PEABr into a glass bottle and add 1 ml DMSO as a perovskite precursor solution. Put the perovskite precursor solution on a stirring table and stir it at room temperature for 12 hours. Finally, filter it through a 0.22-micron filter head and put it into another glass bottle.

[0018] (2) Preparation of blue perovskite light-emitting diodes: The substrate 1 printed with the ITO anode was ultrasonically cleaned with deionized water and anhydrous ethanol for 15 minutes respectively, and treated with ultraviolet ozone for 15 minutes. The filtered PEDOT:PSS was then spin-coated on a glass substrate (at a speed of 4000 rpm for 40 seconds) as a PEDOT:PSS hole transport layer 2, and annealed at 150 degrees Celsius for 15 minutes. Then, PVK was dissolved in chlorobenzene at a concentration of 4 mg / ml and spin-coated on PEDOT:PSS at a speed of 1000 rpm for 40 seconds as a PVK hole transport layer, and annealed at 160 degrees Celsius for 30 minutes. The perovskite precursor solution was spin-coated on the PVK film at a speed of 4000 rpm as a perovskite light-emitting layer 4, and annealed at 100 degrees Celsius for 10 minutes. Finally, it is transferred to the vapor deposition machine, and TPBi, LiF and Al are sequentially deposited as TPBi electron transport layer 5, LiF electron transport layer 6 and Al cathode 7, with thicknesses of 80nm, 1nm and 100nm respectively. The final structure is as follows Figure 1 shown.

[0019] Example 2 (1) Preparation of perovskite precursor solution: Prepare two glass bottles with a volume of 4 ml, clean them with deionized water and ethanol, blow dry them, and put in a clean magnet. Put 73.4 mg PbBr2, 17 mg CsBr, 19.84 mg RbBr and 37.728 mg A6BfPBr into a glass bottle and add 1 ml DMSO as a perovskite precursor solution. Put the perovskite precursor solution on a stirring table and stir it at room temperature for 12 hours. Finally, filter it through a 0.22-micron filter head and put it into another glass bottle.

[0020] (2) Preparation of blue perovskite light-emitting diodes: This part is exactly the same as Example 1.

[0021] Example 3 (1) Preparation of perovskite precursor solution: Prepare two glass bottles with a volume of 4 ml, wash them with deionized water and ethanol, blow dry them, and put in a clean magnet. Put 73.4 mg PbBr2, 17 mg CsBr, 19.84 mg RbBr and 75.456 mg A6BfPBr into a glass bottle and add 1 ml DMSO as a perovskite precursor solution. Put the perovskite precursor solution on a stirring table and stir at room temperature for 12 hours. Finally, filter it through a 0.22-micron filter head and put it into another glass bottle.

[0022] (2) Preparation of blue perovskite light-emitting diodes: This part is exactly the same as Example 1.

[0023] Example 4 (1) Preparation of perovskite precursor solution: Prepare two glass bottles with a volume of 4 ml, wash them with deionized water and ethanol, blow dry them, and put in a clean magnet. Put 73.4 mg PbBr2, 17 mg CsBr, 19.84 mg RbBr and 113.184 mg A6BfPBr into a glass bottle and add 1 ml DMSO as a perovskite precursor solution. Put the perovskite precursor solution on a stirring table and stir at room temperature for 12 hours. Finally, filter it through a 0.22-micron filter head and put it into another glass bottle.

[0024] (2) Preparation of blue perovskite light-emitting diodes: This part is exactly the same as Example 1.

[0025] Example 5 Perovskite precursor solution preparation: Prepare two glass bottles with a volume of 4 ml, wash them with deionized water and ethanol, blow dry them, and put clean magnets in them. Put 73.4 mg PbBr2, 17 mg CsBr, 19.84 mg RbBr and 150.912 mg A6BfPBr into a glass bottle and add 1 ml DMSO as the perovskite precursor solution. Put the perovskite precursor solution on a stirring table and stir it at room temperature for 12 hours. Finally, filter it through a 0.22-micron filter head and put it into another glass bottle.

[0026] (2) Preparation of blue perovskite light-emitting diodes: This part is exactly the same as Example 1.

[0027] Example 6 Perovskite precursor solution preparation: Prepare two glass bottles with a volume of 4 ml, clean them with deionized water and ethanol, blow them dry, and put in a clean magnet. Put 73.4 mg PbBr2, 8.5 mg CsBr, 26.46 mg RbBr and 75.456 mg A6BfPBr into a glass bottle and add 1 ml DMSO as the perovskite precursor solution. Put the perovskite precursor solution on a stirring table and stir it at room temperature for 12 hours. Finally, filter it through a 0.22-micron filter head and put it into another glass bottle.

[0028] (2) Preparation of blue perovskite light-emitting diodes: This part is exactly the same as Example 1.

[0029] Example 7 Perovskite precursor solution preparation: Prepare two glass bottles with a volume of 4 ml, clean them with deionized water and ethanol, blow them dry, and put in a clean magnet. Put 73.4 mg PbBr2, 25.5 mg CsBr, 13.23 mg RbBr and 75.456 mg A6BfPBr into a glass bottle and add 1 ml DMSO as the perovskite precursor solution. Put the perovskite precursor solution on a stirring table and stir it at room temperature for 12 hours. Finally, filter it through a 0.22-micron filter head and put it into another glass bottle.

[0030] (2) Preparation of blue perovskite light-emitting diodes: This part is exactly the same as Example 1.

[0031]

[0032] Table 1 EL performance of blue perovskite LED It can be seen from Table 1 and the attached figure that: with the increase in the amount of A6BfPBr added (Examples 2-5), compared with the blue perovskite light-emitting diode of PEABr, the electroluminescent wavelength of the device did not shift significantly, and the EQE of the LED device was significantly improved. This is because the long organic chain ammonia salt and the large group separation distance create opportunities for the pairing of passivated ammonia and perovskite defect sites, thereby forming a higher quality perovskite light-emitting material. It is worth noting that if the proportion of added RbBr is changed (Examples 6, 3 and 7), the EL emission wavelength of the blue perovskite LED can be adjusted to achieve tunable spectrum.

[0033] The present invention has been described by the above embodiments, but it should be understood that the above embodiments are only for the purpose of example and description, and are not intended to limit the present invention to the described embodiments. In addition, it can be understood by those skilled in the art that the present invention is not limited to the above embodiments, and more variations and modifications can be made according to the teachings of the present invention, and these variations and modifications all fall within the scope of the protection claimed by the present invention. The protection scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A blue perovskite light-emitting diode based on ammonium bromide, characterized in that: The invention comprises a substrate (1) printed with an ITO anode, a PEDOT:PSS hole transport layer (2), a PVK hole transport layer (3), a perovskite light-emitting layer (4), a TPBi electron transport layer (5), a LiF electron transport layer (6) and an Al cathode (7) which are connected in sequence from one side to the other side.

2. The method for preparing a blue perovskite light-emitting diode based on ammonium bromide according to claim 1, characterized in that: The following steps are involved: S1: Place the substrate (1) printed with the ITO anode in a mixed solution of anhydrous ethanol and deionized water, and ultrasonicate it for 20 minutes using an ultrasonic machine, and then blow dry the liquid on its surface with nitrogen; S2: placing the substrate (1) printed with the ITO anode in a UV cleaning agent and cleaning it with UV ozone for 15 minutes; S3: Spin-coating a PEDOT:PSS film on a substrate (1) printed with an ITO anode using a coater and heating it on a hot plate for 15 minutes to form a PEDOT:PSS hole transport layer (2) on the substrate with the ITO anode; S4: Place the substrate (1) printed with the ITO anode in a glove box filled with nitrogen, spin-coat the PVK film, and heat it on a hot plate for 20 minutes to generate a PVK hole transport layer (3) on the PEDOT:PSS hole transport layer (2); S5: After the PVK film is cooled, a perovskite precursor solution is spin-coated on the PVK hole transport layer (3) at a rotation speed of 4000 rpm, and heated at 100° C. for 10 minutes to form a perovskite light-emitting layer (4) on the PVK hole transport layer (3); S6: Finally, the substrate (1) printed with the ITO anode is placed in a vacuum deposition device. When the pressure is less than 4×10 -4 TPBi, LiF and Al thin films were sequentially evaporated at pa with thicknesses of 80nm, 1nm and 100nm, respectively.

3. The method for preparing a blue perovskite light-emitting diode based on ammonium bromide according to claim 2, characterized in that: In S5, the preparation method of the perovskite precursor solution is: PbBr2, CsBr, RbBr and A6BfPBr are placed in a glass bottle and DMSO is added to obtain a configuration solution, and the configuration solution is placed on a stirring table and stirred at room temperature for 12 hours to obtain a perovskite precursor solution.

4. The method for preparing a blue perovskite light-emitting diode based on ammonium bromide according to claim 3, characterized in that: The concentration of PbBr2 in the perovskite precursor solution was 73.4 mg / ml.

5. The method for preparing a blue perovskite light-emitting diode based on ammonium bromide according to claim 3, characterized in that: The concentration of CsBr in the perovskite precursor solution was 0-42.56 mg / ml.

6. The method for preparing a blue perovskite light-emitting diode based on ammonium bromide according to claim 3, characterized in that: The concentration of RbBr in the perovskite precursor solution ranged from 0 to 33.07 mg / ml.

7. The method for preparing a blue perovskite light-emitting diode based on ammonium bromide according to claim 3, characterized in that: The chemical formula of A6BfPBr is: 18 H 21 BrN2O2, chemical structure formula is: 。

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