Hole transport material, preparation method thereof and perovskite solar cell

Abstract

The invention discloses a hole transport material, a preparation method thereof and a perovskite solar cell, and belongs to the technical field of photovoltaic solar materials. The molecular structural formula of the compound is shown as a formula (I) or a formula (II). According to the invention, a quinoxaline part is used as an electron acceptor for extended conjugate modification, a plurality of single donors such as triphenylamine electron donating groups, dihydroacenaphthene, binaphthyloxy and the like are introduced, the hole transport material with a multi-donor structure is constructed, and the hole transport material adjusts the distribution of HOMO-LUMO, increases charge transfer channels, improves the separation and transport capabilities of charges, and improves the hole transport efficiency. Therefore, the mobility of current carriers is improved. A tert-butyl unit is further introduced to the periphery of the triphenylamine group, the hydrophobic property of tert-butyl reduces the interface energy barrier between the hole transport layer and the perovskite precursor solution, directional growth and defect passivation of perovskite crystals are promoted, and the crystallization quality of the perovskite thin film and the device performance are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of photovoltaic solar energy materials, and specifically relates to a hole transport material and a preparation method thereof, and a perovskite solar cell. Background Art

[0002] In the context of the deep integration of new energy and semiconductor technology, perovskite materials, as the core of the third-generation semiconductor technology, have become a research hotspot in the photovoltaic field due to their unique organic-inorganic hybrid semiconductor properties (bandgap adjustable range 1.2~2.3 eV and long exciton diffusion length). The new energy industry (such as solar power generation) has an increasingly urgent demand for high-efficiency, low-cost semiconductor devices, and perovskite semiconductor materials can significantly reduce the levelized cost of electricity (LCOE) of photovoltaic power generation by more than 40% with their low-temperature process (<150℃) prepared by solution method and a theoretical photoelectric conversion efficiency of up to 33% (significantly exceeding the 29.4% limit of crystalline silicon semiconductors), and are regarded as a key path to break through the bottleneck of traditional silicon-based semiconductor photovoltaic technology.

[0003] However, in the large-scale application scenarios of new energy, the rapid development of perovskite is also inseparable from the support of hole transport materials. Among them, the hole transport layer plays a vital role in the extraction and transmission of holes, and the hole transport material is the main component of the hole transport layer. The most commonly used high-efficiency hole transport materials are spiro-OMeTAD and PTAA. Existing hole transport materials have problems such as poor wettability to perovskite precursor solutions and easy crystallization of molecules, which easily lead to poor morphology of perovskite films. Moreover, the acceptor's ability to absorb electrons is too strong, the donor-acceptor energy level does not match, and the high price of materials is also a reason that hinders its commercial application. Summary of the invention

[0004] In order to solve the above problems in the prior art, the purpose of the present invention is to provide a compound.

[0005] Another object of the present invention is to provide use of the above compound as a hole transport material.

[0006] Another object of the present invention is to provide a hole transport material.

[0007] Another object of the present invention is to provide a hole transport layer.

[0008] Another object of the present invention is to provide a perovskite solar cell.

[0009] Another object of the present invention is to provide an application of the above-mentioned perovskite solar cell in the preparation of photovoltaic power generation equipment.

[0010] In order to achieve the above object, the present invention provides the following technical solutions: A compound, the molecular structural formula of the compound is shown in Formula (I) or Formula (II):

[0011] Formula (I)

[0012] Formula (II).

[0013] The present invention is based on the quinoxaline system, and the quinoxaline part is used as an electron acceptor for extended conjugation modification. Single donors such as triphenylamine group, acenaphthene group, and binaphthyloxy group are introduced to construct a multi-donor structure, which can enhance the intermolecular interaction, increase the charge transfer channel, and regulate the distribution of HOMO-LUMO. The two cyano groups (-C≡N) at the molecular terminal are strong electron-withdrawing groups, which attract electrons through the inductive effect. The steric hindrance between donors and intramolecular hydrogen bonds endow the molecule with different rigidities respectively, reduce the rotation and vibration of molecular bonds, inhibit molecular relaxation, and the rigid plane of the molecular acceptor is beneficial to reducing non-radiative transitions, achieving a deep LOMO level, and improving the hole migration efficiency.

[0014] The present invention also protects the application of the above compound as a hole transport material.

[0015] Preferably, the molecular structural formula of the compound is:[[]]END]]

[0016] Formula (I).

[0017] Further introducing a tert-butyl unit outside the triphenylamine group provides good solubility for the hole transport material, is beneficial to the spreading of the hole material and the coating of the perovskite precursor solution, improves the crystallization quality of the perovskite layer, and can also maintain a synergistic donor-acceptor electron effect with the cyano group.

[0018] A hole transport material, comprising a compound with the following molecular structural formula:

[0019] Formula (I)

[0020] Formula (II).

[0021] A hole transport layer, comprising a compound with the following molecular structural formula:

[0022] Formula (I)

[0023] Formula (II).

[0024] The present invention protects the application of the above hole transport material in the preparation of perovskite solar cells.

[0025] A perovskite solar cell sequentially includes a conductive glass layer, a hole transport layer, a perovskite layer, an electron transport layer, and an electrode layer from bottom to top. The hole transport layer includes the above compound or the above hole transport material.

[0026] Specifically, the hole transport layer further includes NiO x , at least one of PTAA, MeO-2PACz, and Me-2PACz.

[0027] Preferably, the hole transport layer sequentially includes a first hole transport layer and a second hole transport layer from bottom to top. The second hole transport layer includes the above compound or the above hole transport material.

[0028] Specifically, the hole transport layer is prepared from a solution of the above compound or the above hole transport material.

[0029] More specifically, in the solution, the concentration of the above compound or the above hole transport material is 0.1~0.3 mg / ml.

[0030] Preferably, in the solution, the concentration of the above compound or the above hole transport material is 0.1 mg / ml.

[0031] More specifically, the solvent in the solution is one or more of DMF, DMSO, THF, acetone, isopropanol, toluene, and chlorobenzene.

[0032] Specifically, the preparation method of the hole transport layer is as follows: spin-coat a solution containing the above compound or the above hole transport material on the surface of the conductive glass, and heat and anneal to obtain the hole transport layer.

[0033] More preferably, the mass ratio of the first hole transport layer to the second hole transport layer is (100~150):(1~10).

[0034] More preferably, the preparation method of the second hole transport layer is as follows: spin-coat a solution containing the above compound or the above hole transport material on the first hole transport layer, and heat and anneal to obtain the second hole transport layer.

[0035] More preferably, the first hole transport layer is NiO x .

[0036] More preferably, the rotation speed of the spin-coating is 3000~5000 rpm.

[0037] More preferably, the spin-coating time is 25~45 s.

[0038] More preferably, the temperature of the heat annealing is 100~180°C.

[0039] More preferably, the time of the heat annealing is 10~50 min.

[0040] Specifically, the conductive glass layer is one of ITO conductive glass or FTO conductive glass.

[0041] Specifically, the perovskite layer comprises formamidinium hydrohalide, alkylammonium halide, cesium halide and lead halide.

[0042] More specifically, the formamidinium halide is at least one of formamidinium hydrochloride, formamidinium bromate and formamidinium iodate.

[0043] More specifically, the alkylammonium halide is at least one of methylammonium iodide, methylammonium chloride and methylammonium bromide.

[0044] More specifically, the cesium halide is at least one of cesium iodide, cesium chloride and cesium bromide.

[0045] More specifically, the lead halide is at least one of lead iodide, lead chloride and lead bromide.

[0046] Preferably, the perovskite layer comprises formamidinium hydroiodide, methylammonium chloride, methylammonium iodide, cesium iodide and lead iodide.

[0047] Specifically, the preparation method of the perovskite layer is as follows: a perovskite solution prepared from the materials of the perovskite layer is spin-coated on the surface of the hole transport layer to obtain the perovskite layer.

[0048] Specifically, the material of the electron transport layer is a C60 derivative.

[0049] More specifically, the C60 derivative is at least one of [6,6]-phenyl C61 butyric acid methyl ester, [6,6]-thienyl C61 butyric acid methyl ester, [6,6]-phenyl-C61-n-octyl butyrate or [6,6]-phenyl-C61-dodecyl butyrate.

[0050] Preferably, the material of the electron transport layer is [6,6]-phenyl C61 butyric acid methyl ester.

[0051] Specifically, the electrode layer is one or more of Pt, Au, Ni, Cu, Ag, In, Ru, Pd, Rh, Ir, Os, C and conductive polymers.

[0052] Preferably, the electrode layer is Ag.

[0053] The present invention also protects the application of the above perovskite solar cell in the preparation of photovoltaic power generation devices.

[0054] Compared with the prior art, the present invention has the following beneficial effects: In the present invention, quinoxaline moiety is used as an electron acceptor for extended conjugation modification, and multiple triphenylamine electron-donating groups, acenaphthene, binaphthyloxy and other single donors are introduced to construct a hole transport material with a multi-donor structure. This hole transport material adjusts the distribution of HOMO-LUMO, increases the charge transfer channels, improves the charge separation and transport capabilities, and thus enhances the carrier mobility. Further, a tert-butyl unit is introduced around the triphenylamine group, significantly improving the solubility of the hole transport material in organic solvents, making its solution easier to uniformly spread into a film; at the same time, the hydrophobic property of the tert-butyl group reduces the interfacial energy barrier between the hole transport layer and the perovskite precursor solution, promotes the oriented growth and defect passivation of perovskite crystals, and improves the crystallization quality and device performance of the perovskite film. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 1H NMR spectrum of Example 1.

[0056] Figure 2 1H NMR spectrum of Example 2.

[0057] Figure 3 J-V curves of perovskite solar cells of Examples 3 to 6 and Comparative Examples 1 and 2.

[0058] Figure 4 Steady-state photoluminescence (PL) spectra of perovskite layers of Examples 3, 6 and Comparative Examples 1 and 2.

[0059] Figure 5 Time-resolved steady-state photoluminescence (TRPL) spectra of perovskite layers of Examples 3, 6 and Comparative Examples 1 and 2.

[0060] Figure 6 XRD patterns of perovskite layers of Example 3 and Comparative Example 1.

[0061] Figure 7 Synthesis route diagram of Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0062] The present invention will be further described below in conjunction with embodiments. These embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. For the experimental methods without specific conditions indicated in the following embodiments, they are generally carried out according to the conventional conditions in the art or according to the conditions recommended by the manufacturer; the raw materials, reagents, etc. used, unless otherwise specified, are all raw materials and reagents that can be obtained from conventional markets and other commercial channels. Any non-substantive changes and substitutions made by those skilled in the art based on the present invention fall within the scope claimed by the present invention.

[0063] Example 1 This embodiment provides a compound or a hole transport material, and the molecular structural formula of the compound or the hole transport material is as follows:

[0064] Formula (I).

[0065] The synthetic route of the above compound is as Figure 7 shown.

[0066] The preparation method of the above compound comprises the following steps: S1: Preparation of 1,4-dibromo-2,3-difluoro-5,6-dinitrobenzene: Put a three-necked flask (250 mL), a spherical condenser, an atmospheric dropping funnel, a glass stopper and a magnetic stirrer into an oven and dry at 100 °C for 30 min. Take out the dried three-necked flask, add 50 mL of trifluoromethanesulfonic acid dropwise thereto, then slowly add 2.5 mL of nitric acid, and stir in an ice bath for 30 min; then, add 5 g of 1,4-dibromo-2,3-difluorobenzene (18.4 mmol) within 30 min, stir at room temperature for 2 h, cool the mixture to 0 °C, then slowly add 2.5 mL of nitric acid, heat to 70 °C and react for 30 h; finally, add sodium hydroxide under ice bath conditions to adjust the pH to neutral, filter and collect to obtain a pale yellow solid with a mass of 4.2 g (yield 68%); The molar ratio of 1,4-dibromo-2,3-difluorobenzene, nitric acid and trifluoromethanesulfonic acid is 1:8:50.

[0067] S2: Preparation of 3,6-dibromo-4,5-difluoro-1,2-benzenediamine: Add 1,4-dibromo-2,3-difluoro-5,6-dinitrobenzene (3 g) and iron powder (7.8 g) to a 250 mL two-necked round-bottom flask, evacuate and purge with nitrogen; then, add acetic acid (70 mL) and start to raise the temperature to 45 °C while stirring, react for 6 h, cool to room temperature, pour the reaction solution into 5 wt% NaOH solution (180 mL), and extract three times with ethyl acetate; finally, wash the ethyl acetate layer with saturated sodium bicarbonate solution, then dry with anhydrous sodium sulfate, distill off ethyl acetate under reduced pressure to obtain a black solid, wash the black solid three times with petroleum ether, filter to obtain a black filter residue with a mass of 1.9 g (yield 87%); The molar ratio of 1,4-dibromo-2,3-difluoro-5,6-dinitrobenzene, iron powder and glacial acetic acid is 1:15:150.

[0068] S3. Preparation of Formula (IV): 3,6-Dibromo-4,5-difluoro-1,2-phenylenediamine (0.265 g), 1,2-dioxo-acenaphthene-5,6-dicarbonitrile (0.232 g) and acetic acid (12 mL) were added to a 50 mL round-bottom flask, and the reaction was carried out under nitrogen protection at 120 °C for 12 h. After cooling, the mixture was poured into water, and the residue was retained by vacuum filtration to obtain the crude product. The crude product was purified by washing (using ethanol as the washing agent) to obtain the solid of the compound of formula (IV), with a mass of 0.31 g (yield 67%); wherein the molar ratio of 1,2-dioxo-acenaphthene-5,6-dicarbonitrile to 3,6-dibromo-4,5-difluoro-1,2-phenylenediamine is 1:1.

[0069] S4. Preparation of the compound of formula (V): The compound of formula (IV) (0.5 g), [1,1'-binaphthalene]-2,2'-diol (0.25 g) and potassium carbonate (0.3 g) were added to a 100 mL two-necked round-bottom flask, 50 mL of dimethyl sulfoxide was added, and the mixture was stirred and heated to 140 °C for 12 h; after the reaction was completed, the reaction solution was poured into 200 mL of water, and then extracted three times with dichloromethane, and the organic phase was collected; the dichloromethane in the organic phase was removed by distillation under reduced pressure, and finally silica gel column chromatography was carried out using dichloromethane and petroleum ether as the eluent to obtain the solid of the compound of formula (V), with a mass of 0.4 g (yield 62%); wherein the molar ratio of the compound of formula (IV), potassium carbonate and the donor group [1,1'-binaphthalene]-2,2'-diol is 1:40:3.

[0070] S5. Preparation of the above compound: 4'.4'-Di-tert-butyl-4-boronic acid pinacol ester triphenylamine (0.665 g), the compound of formula (V) (0.462 g), K 2 CO 3 (0.635 g), Pd(PPh 3 ) 4 (115 mg) and 50 mL of toluene / H 2 O / ethanol (mass ratio 4:2:1) were added to a three-necked flask (250 mL) under nitrogen protection. Then, the mixture was stirred at 110 °C for 16 h. After the reaction was completed, distilled water was poured into the mixture and extracted three times with CH 2 Cl 2 (50 mL×3), and the organic solvent was removed under reduced pressure. The crude product was purified by silica gel column chromatography using CH 2 Cl 2 / petroleum ether (5:1, v:v) as the eluent. The product was further purified by sublimation to obtain the above compound (0.56 g, 70%). 11H NMR (400 MHz, CDCl 3 ) δ 8.41 (d, J = 7.3 Hz, 2H), 8.32 (d, J = 7.3 Hz,2H), 7.97 (s, 2H), 7.74 (d, J = 8.6 Hz, 4H), 7.33 (t, J = 7.8 Hz, 8H), 7.25(d, J = 7.7 Hz, 12H), 7.09 (t, J = 7.3 Hz, 4H). Anal. Calcd for C 92 H 76 N 6 O 2 : C,85.15; H, 5.90; N, 6.48; O, 2.47. The specific 1H NMR spectrum is as shown in Figure 1 .

[0071] Among them, the molar ratio of the compound of formula (V), K 2 CO 3 , the palladium-containing coupling agent and 4',4'-di-tert-butyl-4-boronic acid pinacol ester triphenylamine is 1:40:0.12:2.3.

[0072] Example 2 This example provides a compound or a hole transport material, and the molecular structural formula of the compound or hole transport material is as follows:

[0073] Formula (II).

[0074] In the preparation method of the above compound, steps S1 to S4 are the same as those in Example 1, and the differences are as follows: S5. Add 4-boronic acid pinacol ester triphenylamine (0.61 g), the compound of formula (V) (0.462 g), K 2 CO 3 (0.635 g), Pd(PPh 3 ) 4 (115 mg) and 50 mL of toluene / H 2 O / ethanol (4:2:1) into a three-necked flask (250 mL) under nitrogen protection. Then, stir the mixture at 110 °C for 16 h. After the reaction is completed, pour distilled water into the mixture and extract it three times with CH 2 Cl 2 (50 mL × 3), and then remove the organic solvent under reduced pressure. The crude product is purified by silica gel column chromatography with CH 2 Cl 2Petroleum ether (5:1, v:v) was used as the eluent. The product was further purified by sublimation to obtain the above compound (0.53 g, 65%). 1 H NMR (400 MHz, Chloroform-d) δ 8.32 (d, J = 7.3 Hz, 2H), 8.25 (dd, J = 7.4, 1.4 Hz, 2H), 7.92 (dd, J = 8.7, 2.9 Hz, 4H), 7.58 (d, J = 8.5 Hz, 2H), 7.52 (d, J = 8.3 Hz, 4H), 7.49 – 7.44 (m, 3H), 7.37 (dd, J = 8.4, 6.8 Hz, 3H), 7.27 – 7.23 (m, 7H), 7.22 – 7.16 (m, 15H), 7.03 (td, J = 7.2, 1.4 Hz, 5H). Anal. Calcd for C 76 H 44 N 6 O 2 : C, 85.06; H, 4.13; N, 7.83; O, 2.98. The specific 1H NMR spectrum is as Figure 2 shown.

[0075] Example 3 This example provides a perovskite solar cell, using the compound in Example 1 as the hole transport material, and the hole transport layer includes the compound in Example 1. Its preparation method includes the following steps: S1: The ITO conductive glass substrate was successively cleaned with detergent and deionized water. After drying, it was treated with ultraviolet ozone for 15 min. After the treatment, 40 μL of 15 mg / mL NiO x solution was spin-coated on the surface of the conductive glass layer in air at a spin-coating speed of 4000 rpm for 30 s. After spin-coating, it was transferred to a heating stage and annealed at 150 °C for 30 min to obtain the first hole transport layer; S2: The compound in Example 1 was used as the hole transport material and dissolved in isopropanol to obtain a solution with a concentration of 0.1 mg / mL. In a glove box under a nitrogen atmosphere, 40 μL of the above solution with a concentration of 0.1 mg / ml was dropped on the first hole transport layer and spin-coated at a spin-coating speed of 4000 rpm for 30 s. Then it was transferred to a heating stage and annealed at 100 °C for 10 min to obtain the second hole transport layer; S3: Dissolve formamidinium hydroiodide, methylammonium chloride, methylammonium iodide, cesium iodide, and lead iodide in DMF and DMSO to obtain a perovskite solution. In a glove box under a nitrogen atmosphere, spin-coat 68 μL of the perovskite solution on the surface of the second hole transport layer. First, spin-coat at a speed of 1000 rpm for 10 s, then spin-coat at a speed of 5000 rpm for 30 s. Drop chlorobenzene in the last 10 s, and then transfer it to a heating stage at 100 °C and heat for 30 min to obtain a perovskite layer; S4: In a glove box under a nitrogen atmosphere, dissolve 23 mg of the electron transport layer material [6,6]-phenyl C61 butyric acid methyl ester (PC61BM) in 1 mL of chlorobenzene to prepare a PC61BM electron transport layer solution. Take 28 μL of the PC61BM electron transport layer solution and spin-coat it on the surface of the perovskite modification layer. The spin-coating speed is 3000 rpm, and the spin-coating time is 30 s. After spin-coating, transfer it to a heating stage at 65 °C and heat for 10 min. Then, spin-coat 35 μL of 2.5 mg / mL bathocuproine (BCP) at a spin-coating speed of 5000 rpm and a spin-coating time of 30 s to obtain an electron transport layer; S5: Put the device coated with the electron transport layer into a vacuum coater, evacuate the air, put the silver metal source into a tungsten boat, and evaporate the silver electrode to obtain a perovskite solar cell.

[0076] Example 4 This example provides a perovskite solar cell, which is different from Example 3 in that: S2: Use the compound in Example 1 as the hole transport material and dissolve it in isopropanol to obtain a solution with a concentration of 0.2 mg / mL. In a glove box under a nitrogen atmosphere, drop 40 μL of the 0.2 mg / ml solution on the first hole transport layer. The rest is the same as in Example 3.

[0077] Example 5 This example provides a perovskite solar cell, which is different from Example 3 in that: S2: Use the compound in Example 1 as the hole transport material and dissolve it in isopropanol to obtain a solution with a concentration of 0.3 mg / mL. In a glove box under a nitrogen atmosphere, drop 40 μL of the 0.3 mg / ml solution on the first hole transport layer. The rest is the same as in Example 3.

[0078] Example 6 This example provides a perovskite solar cell, which is different from Example 3 in that S2: Use the compound in Example 2 as the hole transport material and dissolve it in isopropanol to obtain a solution with a concentration of 0.1 mg / mL. In a glove box under a nitrogen atmosphere, drop 40 μL of the 0.1 mg / ml solution on the first hole transport layer. The rest is the same as in Example 3.

[0079] Comparative Example 1 This comparative example provides a perovskite solar cell, which is different from Example 3 in that the hole transport layer does not include the compound in Example 1 (i.e., there is no second hole transport layer). In the preparation method, step S2 is absent, and the rest is the same as in Example 3.

[0080] Comparative Example 2 This comparative example provides a perovskite solar cell, and the hole transport layer includes a dibenzophenanthridine compound represented by the following formula (III),

[0081] Formula (III).

[0082] The difference in its preparation method from Example 3 is that the compound in Example 1 is replaced by the dibenzophenanthridine compound. The rest is the same as in Example 3.

[0083] Performance Test 1 HNMR test: Measured using a Bruker-400 nuclear magnetic resonance spectrometer, and the solvent is deuterated chloroform; Current density-voltage (J-V) characteristic curve test: The performance of the device is evaluated by measuring the J-V characteristic curve. In the experiment, a solar simulator is used to provide AM 1.5G, 100 mWcm -2 of radiant light. A Keithley 2400C digital source meter is used to apply a bias voltage across the test cell and measure the current in its external circuit to obtain the J-V characteristic curve. The effective area of the device is 0.04 cm 2 .

[0084] Steady-state fluorescence emission (PL) spectrum characterization test: For fluorescence emission characterization, a quartz sheet or a glass sheet is used as a substrate to prepare samples. The test sample is spin-coated with a perovskite layer on a transparent conductive glass to form a complete sample. When measuring the steady-state PL, a xenon lamp is used as the excitation light source. When measuring the transient PL, another excitation light source is used. When fitting the transient PL lifetime, a double-exponential fitting method is used, and it is ensured that the fitting index χ 2 is approximately 1 to ensure the reliability of the fitting. The test structures of Examples 3 to 6 are ITO / NiO x / hole transport material / perovskite layer, and the test structure of Comparative Example 1 is ITO / NiO x / perovskite layer.

[0085] X-ray diffraction (XRD) characterization test: For fluorescence emission characterization, a quartz sheet or a glass sheet is used as a substrate to prepare samples. The test sample is coated with a hole transport layer on a transparent conductive glass, and then a perovskite layer is spin-coated to form a complete sample. The scanning angle is 10~45°.

[0086] Figure 3J-V curves of the perovskite solar cells of the examples and comparative examples. The results are shown in Table 1.

[0087] Table 1 J-V test results of the perovskite solar cells of the examples and comparative examples

[0088] As can be seen from Table 1, when using the hole transport materials provided in Example 1 or 2 as the hole transport layer of the perovskite solar cell, the photoelectric conversion efficiency of the perovskite solar device is generally better than that of the perovskite solar device without adding a hole transport material (i.e., Comparative Example 1), and also better than that of the perovskite solar device using a dibenzophenazine compound as the hole transport material (i.e., Comparative Example 2). This shows that the hole transport material provided by the present invention plays a role in promoting carrier transport and has a significant improvement effect on the photoelectric conversion efficiency of the perovskite device.

[0089] Figure 4 Steady-state photoluminescence (PL) spectra of the perovskite layers of Examples 3, 6 and Comparative Examples 1, 2. As can be seen from the figure, the fluorescence peak emission intensity of Examples 3 and 6 is lower than that of Comparative Examples 1 and 2. The decrease in fluorescence intensity indicates a reduction in non-radiative recombination of photo-generated carriers in the perovskite layer. Introducing the hole transport material provided in Example 1 into the HTL, the energy level matching between this hole transport material and the perovskite is optimized to form a more efficient charge transport channel, effectively promoting the rapid extraction of holes from the perovskite layer to the electrode and reducing the accumulation and recombination of carriers inside the perovskite.

[0090] Figure 4 Time-resolved photoluminescence (TRPL) spectra of the perovskite layers of Examples 3, 6 and Comparative Examples 1, 2. As can be seen from the figure, the fluorescence lifetime curves of the perovskite layers of Examples 3 and 6 are lower than those of Comparative Examples 1 and 2, indicating that the average carrier lifetime of the perovskite thin films in Examples 3 and 6 is shortened. This is because the hole transport material provided in Example 1 as the hole transport layer of the perovskite solar cell can improve the hole migration efficiency and effectively reduce the non-radiative recombination and loss of photo-generated carriers.

[0091] Table 2 Biexponential fitting results of the TRPL spectra of Examples 3, 6 and Comparative Examples 1, 2

[0092] Calculate the hole mobility and diffusion length under the ITO / NiO x / hole transport material / perovskite layer structure according to the fitting data of the TRPL spectrum. The results are shown in Table 3.

[0093] Table 3 Charge diffusion length and mobility results of Examples 3, 6 and Comparative Examples 1, 2

[0094] TRPL analysis can reveal the carrier recombination rate and the dominant mechanism by analyzing the decay behavior of photoluminescence intensity over time. The fitting results are shown in Table 2. As can be seen from Table 2, the average carrier lifetimes of the perovskite films in Comparative Example 1 and Comparative Example 2 are 196.35 ns and 193.19 ns respectively, while the average carrier lifetimes of the perovskite films in Example 6 and Example 3 are 150.39 ns and 110.45 ns respectively, τ 1 represents the surface / grain boundary recombination-dominated process, and τ 1 of Comparative Example 1 is 36.48 ns, τ 1 of Comparative Example 2 is 39.83 ns, and τ 1 of Example 3 is extended to 43.77 ns, indicating that the hole transport material provided by the present invention improves the surface recombination lifetime. τ 2 represents the bulk recombination process. τ 2 of Comparative Example 1 is 210.21 ns, τ 2 of Comparative Example 2 is 196.48 ns, and τ 2 of Example 3 drops to 127.90 ns. The bulk lifetime decreases but the surface lifetime increases, indicating that the bulk defects are significantly reduced after the surface optimization of this hole transport material.

[0095] As can be seen from Table 3, the hole mobilities of the perovskite films in Comparative Example 1 and Comparative Example 2 are 27.27 cm 2 V -1 s -1 and 27.89 cm 2 V -1 s -1 respectively, and the hole mobilities of the perovskite films in Example 6 and Example 3 are 38.90 cm 2 V -1 s -1 and 56.88 cm 2 V -1 s -1 respectively. This indicates that compared with Comparative Examples 1 and 2, the hole transport materials in Examples 3 and 6 not only optimize the molecular packing but also reduce the transport barrier through energy level matching (HOMO aligned with the valence band of perovskite), optimize the transport path, and achieve efficient carrier transport.

[0096] Figure 5XRD patterns of Example 3 and Comparative Example 1 are shown. In the XRD patterns, the diffraction peaks at 14.4° respectively represent the (110) crystal plane of perovskite. It can be seen from the figure that the diffraction angle of Example 3 has not changed significantly, indicating that the hole transport material provided in Example 1 does not change the perovskite structure. Compared with Comparative Example 1, the intensity of the diffraction peak corresponding to the (110) crystal plane of Example 3 increases, which shows that the hole transport material provided in Example 1 as the hole transport layer enhances the preferred orientation of perovskite grains and improves the crystallization quality of the perovskite layer.

[0097] Obviously, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A compound, characterized in that The molecular structure of the compound is shown in formula (I) or formula (II): Formula (I) Formula (II).

2. Use of the compound as claimed in claim 1 as a hole transport material.

3. The application according to claim 1, characterized in that: The molecular structure of the compound is: Formula (I).

4. A hole transport material, characterized in that Including compounds with the following molecular formula: Formula (I) Formula (II).

5. A hole transport layer, characterized in that: Including compounds with the following molecular formula: Formula (I) Formula (II).

6. A perovskite solar cell, comprising, from bottom to top, a conductive glass layer, a hole transport layer, a perovskite layer, an electron transport layer and an electrode layer, characterized in that: The hole transport layer comprises the compound according to claim 1 or the hole transport material according to claim 4.

7. The perovskite solar cell according to claim 6, characterized in that: The hole transport layer includes a first hole transport layer and a second hole transport layer in order from bottom to top, and the second hole transport layer includes the compound according to claim 1 or the hole transport material according to claim 4.

8. The perovskite solar cell according to claim 6, characterized in that: The hole transport layer is prepared from the compound according to claim 1 or the solution of the hole transport material according to claim 4.

9. The perovskite solar cell according to claim 8, characterized in that: In the solution, the concentration of the compound according to claim 1 or the hole transport material according to claim 4 is 0.1-0.3 mg / ml.

10. Use of the perovskite solar cell according to any one of claims 6 to 9 in preparing photovoltaic power generation equipment.

Images