Perovskite solar cell doped with a hole transport layer and a bifunctional oxidant and a preparation method thereof

Abstract

The application relates to a perovskite solar cell doped with a hole transport layer bifunctional oxidant and a preparation method thereof, and belongs to the technical field of perovskite solar cell preparation. The bifunctional oxidant (2-iodoxybenzoic acid) used in the application can accelerate the conversion of spiro-OMeTAD to spiro-OMeTAD + under an N2 atmosphere, avoids the adverse effects of water and oxygen on the stability of the device during a long air oxidation process, the generated cations can improve the conductivity and hole mobility of the hole transport layer, the reduction product of 2-iodoxybenzoic acid is o-iodobenzoic acid, the functional groups (-C=O and -I) contained in the o-iodobenzoic acid can effectively passivate uncoordinated lead ions on the surface of the perovskite active layer, thereby reducing the defect state density on the perovskite surface, and finally, the method of doping spiro-OMeTAD with 2-iodoxybenzoic acid can improve the photoelectric conversion efficiency and long-term stability of the perovskite solar cell.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of preparation of perovskite solar cells, and relates to a perovskite solar cell with a hole transport layer doped with a bifunctional oxidizing agent and a preparation method thereof. BACKGROUND

[0002] Organic-inorganic hybrid perovskite solar cells have become a research hotspot in the current photovoltaic field due to their excellent photoelectric conversion efficiency, low cost and easy preparation. So far, with the continuous progress of material engineering and device physics, the efficiency of perovskite solar cells has exceeded 25%. In perovskite solar cells, the hole transport material plays a decisive role in the efficiency and stability of the device. So far, most high-performance perovskite solar cells have adopted spiro-OMeTAD as the hole transport layer because it matches the energy level of perovskite, has good film-forming ability and good thermal stability. However, such devices still need a long time of air oxidation to achieve optimal efficiency. During the air oxidation process, water and oxygen contained in the air will penetrate from the hole transport layer to the perovskite layer, thereby seriously affecting the efficiency and stability of the device.

[0003] Therefore, more and more researches have proposed to accelerate the oxidation process of spiro-OMeTAD by chemical pre-oxidation strategies, such as cobalt salt complexes (FK102, FK209, FK269), copper salt (CuSCN), tris(pentafluorophenyl)borane (BCF), FeCl3, benzoyl peroxide (BPO) and other oxidants have been successfully used as p-type dopants (the addition of these oxidants can accelerate the oxidation of spiro-OMeTAD, thereby effectively improving the conductivity and hole mobility of the hole transport layer); however, unfortunately, many oxidants are difficult to be used for commercial production of perovskite solar cells due to their complex preparation process and high cost. In addition, after the redox reaction between the oxidant and spiro-OMeTAD, new organic substances or low-valent metal cations will be generated, which may exist as impurities in the device. Worse still, the effect of these impurities on the performance of the device is uncertain, or they are harmful to the perovskite material. In addition to the effect of air oxidation on the performance of the device, the surface defects of the perovskite layer will also affect the efficiency and stability of the device.

[0004] Therefore, it is urgent to develop a new type of oxidant that is efficient, low-cost and can passivate the surface defects of perovskite, so as to be able to be incorporated into the hole transport material of perovskite solar cells to improve the related performance of perovskite solar cells. SUMMARY

[0005] Therefore, one of the purposes of the present application is to provide a perovskite solar cell doped with a hole transport layer and a dual functional oxidant; and another purpose of the present application is to provide a preparation method of the perovskite solar cell doped with a hole transport layer and a dual functional oxidant.

[0006] To achieve the above-mentioned purposes, the present application provides the following technical solutions.

[0007] 1. A perovskite solar cell doped with a hole transport layer and a dual functional oxidant, wherein the hole transport layer of the perovskite solar cell contains 2-iodoxybenzoic acid.

[0008] The chemical structural formula of the 2-iodoxybenzoic acid is as follows:

[0009] Preferably, the precursor solution used in the hole transport layer contains spiro-OMeTAD and 2-iodoxybenzoic acid, wherein the concentration of the 2-iodoxybenzoic acid in the precursor solution is not greater than 3 mg / mL.

[0010] Preferably, the precursor solution is prepared by the following method: 2,2',7,7'-tetra[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-OMeTAD) is dissolved in 1 mL of chlorobenzene, then lithium bis-trifluoromethanesulfonimide (Li-TFSI) and 4-tert-butylpyridine (tBP) are added, and finally 2-iodoxybenzoic acid is added and stirred, wherein the mass-volume ratio of the 2,2',7,7'-tetra[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-OMeTAD), lithium bis-trifluoromethanesulfonimide (Li-TFSI) and 4-tert-butylpyridine (tBP) is 72.5-75.0:17.5-18.5:28.5-29.5, mg:uL:uL.

[0011] Preferably, the perovskite solar cell sequentially comprises a fluorine-doped tin oxide glass (FTO) substrate, a dense TiO2 layer, a mesoporous TiO2 layer, a perovskite active layer, a hole transport layer and an electrode layer from bottom to top.

[0012] Further preferably, the material of the electrode layer is metal gold.

[0013] 2. The preparation method of the perovskite solar cell, comprising the following steps:

[0014] (1) A dense TiO2 precursor solution is sprayed on a pretreated fluorine-doped tin oxide glass (FTO) substrate by a spray pyrolysis method, and after being kept at 430-470℃ for 50-70 min, the dense TiO2 layer is formed by cooling to room temperature.

[0015] (2) spin-coat mesoporous TiO2 solution on the compact TiO2 layer, heat at 100-120℃ for 10-20min, then heat at 430-470℃ for 25-35min to form mesoporous TiO2 layer;

[0016] (3) spin-coat perovskite precursor solution, which has been stirred overnight at room temperature, on the mesoporous TiO2 layer, anneal at 110-130℃ for 55-65min to form perovskite active layer;

[0017] (4) dope 2-iodoxybenzoic acid into spiro-OMeTAD solution to make the concentration of 2-iodoxybenzoic acid no more than 3mg / mL, then spin-coat it on the perovskite active layer to form hole transport layer;

[0018] (5) deposit metal electrode on the surface of the hole transport layer under vacuum condition with pressure no more than 10 -5 Pa to form electrode layer.

[0019] Preferably, in step (1), the pretreatment is specifically: firstly, ultrasonic treat fluorine-doped tin oxide glass (FTO) substrate in tap water, deionized water and anhydrous ethanol in sequence, then blow dry with nitrogen flow, and then treat with oxygen plasma to form pretreated fluorine-doped tin oxide glass (FTO) substrate.

[0020] The compact TiO2 precursor solution is isopropanol solution containing isopropyl titanate and acetylacetone, wherein the concentration of isopropyl titanate is 0.18-0.23M and the concentration of acetylacetone is 1.8-2.2M.

[0021] Preferably, in step (2), the mass ratio of mesoporous TiO2 to anhydrous ethanol in the mesoporous TiO2 solution is 1:6.

[0022] Preferably, in step (3), the concentration of PbI2 in the perovskite precursor solution is 1.25-1.35M, the concentration of CsI is 0.06-0.08M, the concentration of methyl bromide amine (MABr2) is 0.13-0.15M, the concentration of PbBr2 is 0.13-0.15M, and the concentration of formamide (FAI) is 1.1-1.3M, wherein the solvent of the perovskite precursor solution is mixed solvent formed by DMF and DMSO in a volume ratio of 4:1.

[0023] In step (3), 80-120uL of anti-solvent is dropped at 14-16s before the end of the spin-coating process, wherein the anti-solvent is chlorobenzene and the volume ratio of the anti-solvent to the perovskite precursor solution is 4:1-6:1.

[0024] Preferably, the temperature of the spray pyrolysis is 430-470 DEG C.

[0025] In step (1), the spraying is specifically as follows: after the tin oxide glass substrate is heated to 430-470 DEG C, the dense TiO2 precursor solution is sprayed onto the FTO substrate, and uniform spraying is repeatedly performed;

[0026] In step (2), the spin coating is specifically as follows: first, coating is performed at a speed of 300-400 rpm for 3-5 s, and then coating is performed at a speed of 4500-5500 rpm for 25-35 s;

[0027] In step (3), the spin coating is specifically as follows: first, coating is performed at a speed of 1000-2000 rpm for 8-12 s, and then coating is performed at a speed of 5500-6500 rpm for 25-35 s;

[0028] In step (4), the spin coating is specifically as follows: coating is performed at a speed of 5500-6500 rpm for 25-35 s.

[0029] The perovskite solar cell disclosed by the application has the following beneficial effects: the perovskite solar cell has a hole transport layer doped with a bifunctional oxidant (2-iodoxybenzoic acid), the bifunctional oxidant (2-iodoxybenzoic acid) can accelerate the conversion of spiro-OMeTAD to spiro-OMeTAD under N2 atmosphere, thereby avoiding the adverse effects of water and oxygen on the stability of the device during the long air oxidation process; the generated cation (spiro-OMeTAD) can improve the conductivity and hole mobility of the hole transport layer; in addition, the reduction product of 2-iodoxybenzoic acid is o-iodobenzoic acid, which contains functional groups (-C=O and -I) and can effectively passivate uncoordinated lead ions on the surface of the perovskite active layer, thereby reducing the defect state density on the surface of the perovskite; finally, the method of doping spiro-OMeTAD with 2-iodoxybenzoic acid can improve the photoelectric conversion efficiency and long-term stability of the perovskite solar cell. + + The perovskite solar cell disclosed by the application has the following beneficial effects: the perovskite solar cell has a hole transport layer doped with a bifunctional oxidant (2-iodoxybenzoic acid), the bifunctional oxidant (2-iodoxybenzoic acid) can accelerate the conversion of spiro-OMeTAD to spiro-OMeTAD under N2 atmosphere, thereby avoiding the adverse effects of water and oxygen on the stability of the device during the long air oxidation process; the generated cation (spiro-OMeTAD) can improve the conductivity and hole mobility of the hole transport layer; in addition, the reduction product of 2-iodoxybenzoic acid is o-iodobenzoic acid, which contains functional groups (-C=O and -I) and can effectively passivate uncoordinated lead ions on the surface of the perovskite active layer, thereby reducing the defect state density on the surface of the perovskite; finally, the method of doping spiro-OMeTAD with 2-iodoxybenzoic acid can improve the photoelectric conversion efficiency and long-term stability of the perovskite solar cell.

[0030] Other advantages, objects, and features of the application will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following specification or can be learned from practice of the application. The objects and other advantages of the application can be realized and attained by the methods and compositions particularly pointed out in the written description and claims hereof. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to make the objects, technical solutions and advantages of the application clearer, the preferred detailed description of the application will be made below with reference to the drawings, in which: In order to make the objects, technical solutions and advantages of the application clearer, the preferred detailed description of the application will be made below with reference to the drawings, in which:

[0032] Figure 1 Structure diagram of perovskite solar cell doped with 2-iodoxybenzoic acid prepared in Example 1;

[0033] Figure 2 Structure diagram of perovskite solar cell without doping prepared in Comparative Example;

[0034] Figure 3 UV absorption spectrum of different spiro-OMeTAD solutions, wherein a is the spiro-OMeTAD solution added with 2-iodoxybenzoic acid in a concentration of 2 mg / mL in Example 1, b is the spiro-OMeTAD solution oxidized by air in Comparative Example, and c is the solution of spiro-OMeTAD prepared in Comparative Example;

[0035] Figure 4 Fourier infrared spectrum of o-iodobenzoic acid (a) and o-iodobenzoic acid plus lead iodide (b);

[0036] Figure 5 J-V curve test result diagram of perovskite solar cell with hole transport layer doped with bifunctional oxidant prepared in Example 1 (a) and perovskite solar cell prepared in Comparative Example (b);

[0037] Figure 6 J-V curve test results of perovskite solar cells doped with different concentrations of 2-iodoxybenzoic acid in Comparative Example, Example 1 and Example 2;

[0038] Figure 7 External quantum efficiency test results of perovskite solar cell with hole transport layer doped with bifunctional oxidant prepared in Example 1 (a) and perovskite solar cell prepared in Comparative Example (b).

[0039] Figure 8 Long-term stability test results of perovskite solar cell with hole transport layer doped with bifunctional oxidant prepared in Example (a) and perovskite solar cell prepared in Comparative Example (b).

[0040] Figure 9 J-V curve test result diagram of perovskite solar cell with hole transport layer doped with bifunctional oxidant prepared in Example 1 (a), Example 3 (b) and Example 4 (c); DETAILED DESCRIPTION

[0041] Following, the embodiments of the present application will be described in detail by specific examples. Other advantages and effects of the present application can be easily understood by those skilled in the art from this disclosure. The present application can also be implemented or applied by other different embodiments, and various modifications or changes can be made to the details based on different views and applications without departing from the spirit of the present application. It should be noted that the drawings provided in the following examples only illustrate the basic concept of the present application in a schematic manner, and the following examples and features in the examples can be combined with each other without conflict.

[0042] Example 1

[0043] A perovskite solar cell doped with a hole transport layer and a bifunctional oxidant, the specific preparation method comprising the following steps:

[0044] (1) Preparation of a pretreated fluorine-doped tin oxide glass (FTO) substrate: first, the fluorine-doped tin oxide glass (FTO) substrate is sequentially ultrasonically treated in tap water, deionized water and anhydrous ethanol, then blown dry with a nitrogen stream, and then treated with oxygen plasma to form a pretreated fluorine-doped tin oxide glass (FTO) substrate;

[0045] (2) Preparation of a dense TiO2 layer: a dense TiO2 precursor solution (the solvent of the dense TiO2 precursor solution is isopropanol and contains isopropyl titanate with a concentration of 0.2M and acetylacetone with a concentration of 2.0M) is sprayed by a spray pyrolysis method (specifically, after the FTO substrate is heated to 450℃, the dense TiO2 precursor solution is sprayed onto the FTO substrate, and uniform spraying is repeatedly performed; ) on the pretreated fluorine-doped tin oxide glass (FTO) substrate in step (1), and after being kept at 450℃ for 60min and cooled to room temperature, a dense TiO2 layer is formed;

[0046] (3) Preparation of a mesoporous TiO2 layer: a mesoporous TiO2 solution (the mass ratio of mesoporous TiO2 to anhydrous ethanol in the mesoporous TiO2 solution is 1:6) is spin-coated (first at a speed of 350rpm for 4s, then at a speed of 5000rpm for 30s) on the dense TiO2 layer formed in step (2), heated at 110℃ for 15min, and then heated at 450℃ for 30min to form a mesoporous TiO2 layer;

[0047] (4) Preparation of perovskite active layer: spin-coat (firstly coat for 10 s at a speed of 1500 rpm, then coat for 30 s at a speed of 6000 rpm) the mesoporous TiO2 layer formed in step (3) with the perovskite precursor solution (the solvent of the perovskite precursor solution is a mixed solvent of DMF and DMSO in a volume ratio of 4:1, and the concentration of PbI2 is 1.3 M, the concentration of CsI is 0.07 M, the concentration of MABr2 is 0.14 M, the concentration of PbBr2 is 0.14 M, and the concentration of FAI is 1.19 M) stirred overnight at room temperature, and then anneal at 120°C for 60 min to form a perovskite active layer;

[0048] (5) Preparation of hole transport layer: dope 2-iodoxybenzoic acid into the spiro-OMeTAD solution (the spiro-OMeTAD solution is prepared by dissolving 74 mg of spiro-OMeTAD in 1 mL of chlorobenzene, then adding 18 uL of lithium bis-trifluoromethanesulfonimide (Li-TFSI) and 29 uL of 4-tert-butylpyridine (tBP), so that the concentration of 2-iodoxybenzoic acid is 2 mg / mL), and then spin-coat (coat for 30 s at a speed of 6000 rpm) the perovskite active layer formed in step (4) to form a hole transport layer;

[0049] (6) Preparation of perovskite solar cell: deposit a metal electrode on the surface of the hole transport layer formed in step (5) under vacuum conditions with a pressure of 10 -5 Pa, and then obtain a perovskite solar cell (its structure is shown in Figure 1 FIG. 1) after forming an electrode layer.

[0050] Example 2

[0051] Replace the concentration of 2-iodoxybenzoic acid in step (5) of Example 1 with concentrations of 3.0 mg / mL, 2.5 mg / mL, 1.5 mg / mL, and 1.0 mg / mL, respectively, and the rest of the preparation method is the same as that in Example 1, to prepare perovskite solar cells with different doping amounts.

[0052] Example 3

[0053] A perovskite solar cell with a hole transport layer doped with a bifunctional oxidant, and the specific preparation method comprises the following steps:

[0054] (1) Preparation of pretreated fluorine-doped tin oxide glass (FTO) substrate: firstly, ultrasonically treat the fluorine-doped tin oxide glass (FTO) substrate in tap water, deionized water, and anhydrous ethanol in sequence, then blow dry with a nitrogen stream, and then treat with oxygen plasma to form a pretreated fluorine-doped tin oxide glass (FTO) substrate;

[0055] (2) Preparation of dense TiO2 layer: a dense TiO2 precursor solution (the solvent of which is isopropanol and which contains isopropyl titanate with a concentration of 0.23 M and acetylacetone with a concentration of 2.2 M) is sprayed by the method of spray pyrolysis (specifically, after the FTO substrate is heated to 470°C, the dense TiO2 precursor solution is sprayed onto the FTO substrate, and uniform spraying is repeatedly performed; ) on the fluorine-doped tin oxide glass (FTO) substrate pretreated in step (1) to form a dense TiO2 layer after being kept at 470°C for 50 min and then cooled to room temperature;

[0056] (3) Preparation of mesoporous TiO2 layer: a mesoporous TiO2 solution (the mass ratio of mesoporous TiO2 to anhydrous ethanol in the mesoporous TiO2 solution is 1:6) is spin-coated (firstly coated at a speed of 400 rpm for 3 s, and then coated at a speed of 5500 rpm for 25 s) on the dense TiO2 layer formed in step (2), heated at 120°C for 10 min, and then heated at 470°C for 25 min to form a mesoporous TiO2 layer;

[0057] (4) Preparation of perovskite active layer: a perovskite precursor solution (the solvent of which is a mixed solvent of DMF and DMSO in a volume ratio of 4:1 and the concentrations of PbI2, CsI, MABr2, PbBr2 and FAI are 1.35 M, 0.08 M, 0.15 M, 0.15 M and 1.3 M, respectively) stirred overnight at room temperature is spin-coated (firstly coated at a speed of 2000 rpm for 8 s, and then coated at a speed of 6500 rpm for 25 s) on the mesoporous TiO2 layer formed in step (3) to form a perovskite active layer after being annealed at 130°C for 55 min;

[0058] (5) Preparation of hole transport layer: 2-iodoxybenzoic acid is doped into a spiro-OMeTAD solution (the spiro-OMeTAD solution is prepared by dissolving 75.0 mg of spiro-OMeTAD in 1 mL of chlorobenzene, and then adding 18.5 uL of lithium bis-trifluoromethanesulfonimide (Li-TFSI) and 29.5 uL of 4-tert-butylpyridine (tBP)), so that the concentration of 2-iodoxybenzoic acid is 2 mg / mL, and then it is spin-coated (coated at a speed of 6500 rpm for 25 s) on the perovskite active layer formed in step (4) to form a hole transport layer;

[0059] (6) Preparation of perovskite solar cell: a metal electrode is deposited on the surface of the hole transport layer formed in step (5) under vacuum conditions with a pressure of 10 -5 Pa to form an electrode layer, and thus a perovskite solar cell (the structure of which is shown in Figure 1 ).

[0060] Example 4

[0061] A perovskite solar cell doped with a hole transport layer and a bifunctional oxidant, the specific preparation method comprising the following steps:

[0062] (1) Preparation of a pretreated fluorine-doped tin oxide glass (FTO) substrate: first, the fluorine-doped tin oxide glass (FTO) substrate is sequentially ultrasonically treated in tap water, deionized water and anhydrous ethanol, then dried with a nitrogen stream, and then treated with oxygen plasma to form a pretreated fluorine-doped tin oxide glass (FTO) substrate;

[0063] (2) Preparation of a dense TiO2 layer: a dense TiO2 precursor solution (the solvent of the dense TiO2 precursor solution is isopropanol and contains isopropyl titanate with a concentration of 0.18M and acetylacetone with a concentration of 1.8M) is sprayed by a spray pyrolysis method (specifically, after the FTO substrate is heated to 430℃, the dense TiO2 precursor solution is sprayed onto the FTO substrate, and uniform spraying is repeatedly performed; ) on the pretreated fluorine-doped tin oxide glass (FTO) substrate in step (1), and after being kept at 430℃ for 70min, it is cooled to room temperature to form a dense TiO2 layer;

[0064] (3) Preparation of a mesoporous TiO2 layer: a mesoporous TiO2 solution (the mass ratio of mesoporous TiO2 to anhydrous ethanol in the mesoporous TiO2 solution is 1:6) is spin-coated (first at a speed of 300rpm for 5s, then at a speed of 4500rpm for 35s) on the dense TiO2 layer formed in step (2), and after being heated at 100℃ for 20min and then heated at 430℃ for 35min, a mesoporous TiO2 layer is formed;

[0065] (4) Preparation of a perovskite active layer: a perovskite precursor solution (the solvent of the perovskite precursor solution is a mixed solvent formed by DMF and DMSO in a volume ratio of 4:1, and the concentration of PbI2 is 1.25M, the concentration of CsI is 0.06M, the concentration of MABr2 is 0.13M, the concentration of PbBr2 is 0.13M and the concentration of FAI is 1.1M) stirred overnight at room temperature is spin-coated (first at a speed of 1000rpm for 12s, then at a speed of 5500rpm for 35s) on the mesoporous TiO2 layer formed in step (3), and after being annealed at 110℃ for 65min, a perovskite active layer is formed;

[0066] (5) Preparation of a hole transport layer: 2-iodoxybenzoic acid is doped into a spiro-OMeTAD solution (the spiro-OMeTAD solution is prepared as follows: 72.5 mg of spiro-OMeTAD is dissolved in 1 mL of chlorobenzene, and then 17.5 uL of lithium bis-trifluoromethanesulfonimide (Li-TFSI) and 28.5 uL of 4-tert-butylpyridine (tBP) are added, so that the concentration of 2-iodoxybenzoic acid is 2 mg / mL, which is then spin-coated (coated at a speed of 5500 rpm for 35 s) on the perovskite active layer formed in step (4) to form a hole transport layer;

[0067] (6) Preparation of a perovskite solar cell: a metal electrode is deposited on the surface of the hole transport layer formed in step (5) under vacuum conditions with a pressure of 10 -5 Pa to form an electrode layer, and a perovskite solar cell is obtained (the structure is shown in Figure 1 ).

[0068] Comparative Example

[0069] A perovskite solar cell without a doped bifunctional oxidant, and a specific preparation method includes the following steps:

[0070] (1) Preparation of a pretreated fluorine-doped tin oxide (FTO) substrate: first, a fluorine-doped tin oxide (FTO) substrate is ultrasonically treated in tap water, deionized water and anhydrous ethanol in sequence, and then dried with a nitrogen gas stream, and then treated with oxygen plasma to form a pretreated fluorine-doped tin oxide (FTO) substrate;

[0071] (2) Preparation of a dense TiO2 layer: a dense TiO2 precursor solution (the solvent of the dense TiO2 precursor solution is isopropanol, and the dense TiO2 precursor solution contains isopropyl titanate with a concentration of 0.2 M and acetylacetone with a concentration of 2.0 M) is sprayed (specifically, after the FTO substrate is heated to 450°C, the dense TiO2 precursor solution is sprayed onto the FTO substrate, and uniform spraying is repeatedly performed) on the pretreated fluorine-doped tin oxide (FTO) substrate, and after being kept at 450°C for 60 min, the dense TiO2 layer is formed by cooling to room temperature;

[0072] (3) Preparation of a mesoporous TiO2 layer: a mesoporous TiO2 solution (the mass ratio of mesoporous TiO2 to anhydrous ethanol in the mesoporous TiO2 solution is 1:6) is spin-coated (first coated at a speed of 350 rpm for 4 s, and then coated at a speed of 5000 rpm for 30 s) on the dense TiO2 layer formed in step (2), and after being heated at 110°C for 15 min and then heated at 450°C for 30 min, a mesoporous TiO2 layer is formed;

[0073] (4) Preparation of perovskite active layer: spin-coating (firstly coating at 1500 rpm for 10 s, then coating at 6000 rpm for 30 s) the perovskite precursor solution (the solvent of the perovskite precursor solution is mixed solvent of DMF and DMSO with a volume ratio of 4:1, and the concentration of PbI2 is 1.3 M, the concentration of CsI is 0.07 M, the concentration of MABr2 is 0.14 M, the concentration of PbBr2 is 0.14 M, and the concentration of FAI is 1.19 M) stirred overnight at room temperature on the mesoporous TiO2 layer formed in step (3) to form a perovskite active layer by annealing at 120 °C for 60 min;

[0074] (5) Preparation of hole transport layer: spin-coating (coating at 6000 rpm for 30 s) the spiro-OMeTAD solution (the spiro-OMeTAD solution is prepared by dissolving 74 mg of spiro-OMeTAD in 1 mL of chlorobenzene, then adding 18 uL of lithium bis-trifluoromethanesulfonimide (Li-TFSI) and 29 uL of 4-tert-butylpyridine (tBP)) on the perovskite active layer formed in step (4) to form a hole transport layer;

[0075] (6) Preparation of perovskite solar cell: depositing a metal electrode on the surface of the hole transport layer formed in step (5) under vacuum conditions with a pressure of 10 -5 Pa to form an electrode layer, and then obtaining an undoped perovskite solar cell (the structure is shown in Figure 2 ).

[0076] Performance test

[0077] The performance of the perovskite solar cell doped with the bifunctional oxidant on the hole transport layer prepared in Example 1 was tested using Keithley 2400: the photocurrent-voltage curve was obtained under simulated AM 1.5G sunlight irradiation conditions (light intensity of 100 mW / cm 2 ), forward scanning -0.2 V→1.2 V, scanning rate 50 mV / S.

[0078] The ultraviolet-visible spectrum was measured on a Shimadzu UV-2550 absorption spectrophotometer; Fourier transform infrared spectroscopy (FTIR) analysis was performed using a Thermo Nicolet 6700; external quantum efficiency (EQE) spectra were recorded using a computer-controlled device consisting of a xenon light source (Spectra Products ASB-XE-175), a monochromator (Spectra Products CM110), and a potentiostat (LabJack U6 DAQ board); long-term stability testing was performed on equipment in the glove box.

[0079] Figure 3are UV absorption spectra of different spiro-OMeTAD solutions, wherein a is the spiro-OMeTAD solution with 2-iodoxybenzoic acid added at a concentration of 2 mg / ml in Example 1, b is the spiro-OMeTAD solution that has undergone air oxidation in the comparative example, and c is the original spiro-OMeTAD solution in the comparative example. From Figure 3 It can be seen that the spiro-OMeTAD solution that has undergone air oxidation shows a new absorption peak in the wavelength range of 420-560 nm compared to the original spiro-OMeTAD solution, which can be attributed to the formation of spiro-OMeTAD + . It is worth noting that a higher absorption peak intensity is observed in the spiro-OMeTAD solution containing 2-iodoxybenzoic acid. This result indicates that 2-iodoxybenzoic acid can more effectively oxidize spiro-OMeTAD to spiro-OMeTAD + than normal air oxidation.

[0080] Figure 4 are Fourier infrared spectra of o-iodobenzoic acid (a) and o-iodobenzoic acid with lead iodide (b). From Figure 4 It can be seen that the C=O characteristic peak of o-iodobenzoic acid is located at 1684 cm -1 , and after mixing with PbI2, the position of the C=O peak moves to 1671 cm -1 . This shift in the peak is attributed to the Lewis acid-base interaction between C=O and Pb 2+ .

[0081] Figure 5 are J-V curve test results of the perovskite solar cell prepared in Example 1 with a hole transport layer doped with a bifunctional oxidant (a) and the perovskite solar cell prepared in the comparative example (b). From Figure 5 It can be seen that the photoelectric conversion efficiency (PCE) of the perovskite solar cell prepared in the comparative example is 20.42% (J sc = 23.54 mA / cm 2 , V oc = 1.11 V, FF = 78%), while the perovskite solar cell prepared in Example 1 with a hole transport layer doped with a bifunctional oxidant exhibits an excellent PCE of 22.45% (J sc = 24.13 mA / cm 2 , V oc = 1.14 V, FF = 82%). The increase in FF and Jsc is attributed to the improved conductivity and hole mobility of the hole transport layer after the addition of 2-iodoxybenzoic acid. V ocThe increase is due to the reduction products of 2-iodobenzoic acid passivating the surface defects of the perovskite layer, thereby reducing charge recombination.

[0082] The photoelectric performance parameters of the perovskite solar cell with hole transport layer doped with bifunctional oxidant prepared in Example 1 and the perovskite solar cell prepared in the comparative example are shown in Table 1.

[0083] Table 1. Photoelectric performance parameters of perovskite solar cells prepared by different methods

[0084] Sample J sc (mA / cm 2 )]]> V oc (V)]]> FF PCE (%) Comparative Example 23.54 1.11 0.78 20.42 Example 1 24.13 1.14 0.82 22.45

[0085] Figure 6 To compare the JV curve test results of perovskite solar cells doped with different concentrations of 2-iodobenzoic acid in Examples 1, 2, and 3, from... Figure 6 It can be seen that with the increase of 2-iodobenzoic acid doping concentration, the photoelectric conversion efficiency (PCE) increases from 20.42% to 22.45%, and the PCE shows a decreasing trend when the concentration is greater than 2 mg / mL. This may be because excessive 2-iodobenzoic acid leads to over-oxidation of spiro-OMeTAD, thereby reducing carrier mobility.

[0086] Figure 7 The external quantum efficiency test results are shown for the perovskite solar cell (a) with a hole transport layer doped with a bifunctional oxidant prepared in Example 1 and the perovskite solar cell (b) prepared in the comparative example. Figure 7 It can be seen that after doping with 2-iodobenzoic acid, the integrated current density of the device increased from 22.13 mA / cm². 2 Increased to 22.71 mA / cm 2 This is consistent with the trend of the JV curve test results.

[0087] Figure 8 The long-term stability test results are shown for the perovskite solar cell (a) with a hole transport layer doped with a bifunctional oxidant prepared in Example 1 and the perovskite solar cell (b) prepared in the comparative example. Figure 8 It can be seen that after 1200 hours of storage in the dark, the PCE of the 2-iodobenzoic acid-doped device remains at 91.7% of its initial value, while the PCE of the original device only drops to 79.2% of its initial value. This indicates that the 2-iodobenzoic acid-doped device has good long-term stability.

[0088] Figure 9 The JV curve test results are for the perovskite solar cells with hole transport layers doped with bifunctional oxidants prepared in Examples 1(a), 4(c). Figure 9It can be seen that the performance of the perovskite solar cell with the hole transport layer doped with the bifunctional oxidant prepared in Example 3 and Example 4 is similar to that of the perovskite solar cell with the hole transport layer doped with the bifunctional oxidant in Example 1(a).

[0089] In summary, the present application discloses a perovskite solar cell with a hole transport layer doped with a bifunctional oxidant (2-iodoxybenzoic acid), which can accelerate the conversion of spiro-OMeTAD to spiro-OMeTAD + under N2 atmosphere, thereby avoiding the adverse effects of water and oxygen on the stability of the device during the long air oxidation process; the generated cation (spiro-OMeTAD + ) can improve the conductivity and hole mobility of the hole transport layer; in addition, the reduction product of 2-iodoxybenzoic acid is o-iodobenzoic acid, and the functional groups (-C=O and -I) thereon can effectively passivate the uncoordinated lead ions on the surface of the perovskite active layer, thereby reducing the defect state density on the surface of the perovskite; finally, the method of doping spiro-OMeTAD with 2-iodoxybenzoic acid can improve the photoelectric conversion efficiency and long-term stability of the perovskite solar cell.

[0090] Finally, it should be pointed out that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions, and all such modifications or replacements should be included in the scope of the claims of the present application.

Claims

1. A perovskite solar cell with a hole transport layer doped with a bifunctional oxidant, characterized in that, The hole transport layer of the perovskite solar cell contains 2-iodobenzoic acid. The chemical structural formula of the 2-iodobenzoic acid is: ; The precursor solution used in the hole transport layer contains spiro-OMeTAD and 2-iodobenzoic acid, wherein the concentration of 2-iodobenzoic acid in the precursor solution is no greater than 3 mg / mL. The precursor solution was prepared as follows: 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene was dissolved in 1 mL of chlorobenzene, then lithium bis(trisulfonyl)imide and 4-tert-butylpyridine were added, and finally 2-iodobenzoic acid was added and stirred. The mass-to-volume ratio of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene, lithium bis(trisulfonyl)imide and 4-tert-butylpyridine was 72.5~75.0 : 17.5~18.5 : 28.5~29.5 mg:uL:uL.

2. The perovskite solar cell according to claim 1, characterized in that, The perovskite solar cell comprises, from bottom to top, a fluorine-doped tin oxide glass substrate, a dense TiO2 layer, a mesoporous TiO2 layer, a perovskite active layer, a hole transport layer, and an electrode layer.

3. The perovskite solar cell according to claim 2, characterized in that, The electrode layer is made of metallic gold.

4. The method for preparing the perovskite solar cell according to any one of claims 1 to 3, characterized in that, The preparation method includes the following steps: (1) The dense TiO2 precursor solution was sprayed onto the pretreated fluorine-doped tin oxide glass substrate by spray thermal decomposition. After being kept at 430~470℃ for 50~70 min, it was cooled to room temperature to form a dense TiO2 layer. (2) Spin-coating the mesoporous TiO2 solution onto the dense TiO2 layer, heating at 100~120℃ for 10~20 min and then heating at 430~470℃ for 25~35 min to form a mesoporous TiO2 layer; (3) Spin-coat the perovskite precursor solution that has been stirred overnight at room temperature onto the mesoporous TiO2 layer and anneal it at 110~130℃ for 55~65 min to form a perovskite active layer. (4) 2-Iodobenzoic acid is doped into the spiro-OMeTAD solution so that the concentration of 2-iodobenzoic acid is no more than 3 mg / mL, and then spin-coated onto the perovskite active layer to form a hole transport layer. (5) Under pressure not exceeding 10 -5 Metal electrodes are deposited on the surface of the hole transport layer under vacuum conditions of Pa to form an electrode layer.

5. The preparation method according to claim 4, characterized in that, In step (1), the pretreatment specifically involves: firstly, the fluorine-doped tin oxide glass substrate is ultrasonically treated in tap water, deionized water and anhydrous ethanol in sequence, then dried with nitrogen gas, and then treated with oxygen plasma to form a pretreated fluorine-doped tin oxide glass substrate. The dense TiO2 precursor solution is an isopropanol solution containing isopropyl titanate and acetylacetone, wherein the concentration of isopropyl titanate is 0.18~0.23M and the concentration of acetylacetone is 1.8~2.2M.

6. The preparation method according to claim 4, characterized in that, In step (2), the mass ratio of mesoporous TiO2 to anhydrous ethanol in the mesoporous TiO2 solution is 1:

6.

7. The preparation method according to claim 4, characterized in that, In step (3), the concentration of PbI2 in the perovskite precursor solution is 1.25~1.35 M, the concentration of CsI is 0.06~0.08 M, the concentration of methylammonium bromide is 0.13~0.15 M, the concentration of PbBr2 is 0.13~0.15 M, and the concentration of formamide is 1.1~1.3 M. The solvent of the perovskite precursor solution is a mixed solvent formed by DMF and DMSO with a volume ratio of 4:

1. In step (3), during the spin coating process, 80-120 μL of antisolvent is dropped onto the perovskite precursor solution 14-16 seconds before the end of the spin coating. The antisolvent is chlorobenzene, and the volume ratio of the antisolvent to the perovskite precursor solution is 4:1-6:

1.

8. The preparation method according to claim 4, characterized in that, The temperature of the spray thermal decomposition is 430~470℃; In step (1), the spraying specifically involves heating the tin oxide glass substrate to 430~470℃, then spraying the dense TiO2 precursor solution onto the FTO substrate, and repeatedly performing uniform spraying. In step (2), the spin coating specifically involves: first coating at a speed of 300-400 rpm for 3-5 seconds, and then coating at a speed of 4500-5500 rpm for 25-35 seconds; In step (3), the spin coating specifically involves: first coating at a speed of 1000-2000 rpm for 8-12 seconds, and then coating at a speed of 5500-6500 rpm for 25-35 seconds; In step (4), the spin coating specifically refers to coating at a rotation speed of 5500~6500 rpm for 25~35 seconds.

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