A method for enhancing the performance of perovskite solar cells

Abstract

The present invention provides a method for enhancing the performance of perovskite solar cells, comprising the following steps: mixing a two-dimensional perovskite single crystal with a reagent having surface coordination effect to induce the formation of a two-dimensional perovskite interface at the three-dimensional perovskite interface. Compared with the prior art, the present invention provides a strategy for enhancing the performance of three-dimensional perovskite solar cells with two-dimensional perovskite. By using a two-step method, two-dimensional perovskite modification is first carried out. Based on the chemically modifiable characteristics of the reagent having surface coordination effect, chemical functional groups are introduced to enhance interface modification, so that the two-dimensional perovskite is controllable. Then, the three-dimensional perovskite interface is further optimized. It can not only reflect the role of two-dimensional perovskite in improving stability, but also solve the disadvantage of poor electrical properties of two-dimensional perovskite through coordination modification, achieving the effect of enhancing the performance of perovskite solar cells.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and more specifically, to a method for enhancing the performance of perovskite solar cells. Background Art

[0002] With the continuous consumption of fossil energy and the continuous rise of energy demand, the development of new sustainable energy is one of the important directions of current energy development. Solar energy has the characteristics of rich reserves and environmental protection, and has become the most important energy source in clean energy. Therefore, in recent years, the development of photovoltaic technology has attracted a research boom globally. Organic-inorganic hybrid perovskite solar cells have attracted much attention due to their high theoretical efficiency, low cost, and rich raw material sources. However, the intrinsic instability of organic-inorganic hybrid perovskite materials under water, heat, and light conditions, which leads to the decomposition of perovskite, will affect the long-term stability of the device and further hinder the commercial application of this technology. In recent years, two-dimensional layered perovskite has become one of the important solutions to solve the commercialization of perovskite due to its excellent stability. However, although two-dimensional perovskite can optimize stability, its many grain boundaries, size effects, etc. lead to the generation of energy barriers, the formation of quantum well structures, the widening of the band gap, and have an adverse impact on charge transport. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a method for enhancing the performance of perovskite solar cells. By adopting the strategy of using two-dimensional perovskite to enhance the performance of three-dimensional perovskite solar cells, it can not only reflect the role of two-dimensional perovskite in improving stability, but also solve the disadvantage of poor electrical properties of two-dimensional perovskite through coordination modification.

[0004] The present invention provides a method for enhancing the performance of perovskite solar cells, including the following steps:

[0005] Mix a two-dimensional perovskite single crystal with a reagent having a surface coordination effect to induce the formation of a two-dimensional perovskite interface at the three-dimensional perovskite interface.

[0006] Preferably, the preparation method of the two-dimensional perovskite single crystal is specifically:

[0007] Add an organic salt and an inorganic salt to an acid solution, mix for the first time and then filter, and then mix the filtered mixed solution under an inert atmosphere for the second time, and cool down to obtain a two-dimensional perovskite single crystal;

[0008] The organic salt is FAI, MAI, FACl, MACl, FABr or MABr;

[0009] The inorganic salt is MB2, where M is Pb or Sn, and B is I, Cl, Br or F;

[0010] The acid solution is hydroiodic acid, concentrated nitric acid or concentrated sulfuric acid.

[0011] Preferably, the temperature of the first mixing is 40°C to 60°C, and the time is 20 min to 40 min; the inert atmosphere is an N2 atmosphere; the temperature of the second mixing is 80°C to 100°C, and the time is 1 h to 3 h.

[0012] Preferably, the process of cooling down is specifically:

[0013] Cool down to 40°C to 60°C at a rate of 1°C to 3°C per hour to obtain a two-dimensional perovskite single crystal.

[0014] Preferably, the reagent with surface coordination effect is tyramine hydrochloride or ascorbic acid.

[0015] Preferably, the mass ratio of the two-dimensional perovskite single crystal to the reagent with surface coordination effect is 1:(0.1 - 2).

[0016] Preferably, the two-dimensional perovskite interface exists in:

[0017] Between the three-dimensional perovskite interface and the electron transport layer;

[0018] Or: between the three-dimensional perovskite interface and the hole transport layer;

[0019] Or: simultaneously exist between the three-dimensional perovskite interface and the electron transport layer and between the three-dimensional perovskite interface and the hole transport layer.

[0020] Preferably, the electron transport layer is a SnO2 layer, a TiO2 layer or a C60 and its derivative layer, with a thickness of 10 nm to 100 nm;

[0021] The hole transport layer is a Spiro-OMeTAD layer, a NiOx layer or a CuOx layer, with a thickness of 10 nm to 100 nm.

[0022] Preferably, the thickness of the three-dimensional perovskite interface is 100 nm to 700 nm.

[0023] Preferably, the thickness of the two-dimensional perovskite interface is 20 nm to 500 nm.

[0024] The present invention provides a method for enhancing the performance of perovskite solar cells, comprising the following steps: mixing a two-dimensional perovskite single crystal with a reagent having surface coordination effect to induce the formation of a two-dimensional perovskite interface at the three-dimensional perovskite interface. Compared with the prior art, the present invention provides a strategy for enhancing the performance of three-dimensional perovskite solar cells by two-dimensional perovskite. Firstly, two-dimensional perovskite modification is carried out by a two-step method. Based on the chemically modifiable characteristics of the reagent having surface coordination effect, chemical functional groups are introduced to enhance interface modification, so that the two-dimensional perovskite is controllable. Then, the three-dimensional perovskite interface is further optimized. It can not only reflect the role of two-dimensional perovskite in improving stability, but also solve the disadvantage of poor electrical properties of two-dimensional perovskite through coordination modification, achieving the effect of enhancing the performance of perovskite solar cells.

[0025] In addition, the method provided by the present invention has little influence on the existing preparation process of perovskite solar cells, is easy to implement, has mild and controllable conditions, and has a wide application range, with broad application prospects. Description of the Drawings

[0026] Figure 1 A comparison diagram of the current density versus voltage curves of the perovskite solar cells provided in Example 1 and Comparative Example 1;

[0027] Figure 2 A comparison diagram of the photoelectric conversion efficiency data of the perovskite solar cells provided in Example 1 and Comparative Example 1;

[0028] Figure 3 A scanning electron microscope image showing the three-dimensional perovskite and two-dimensional perovskite structures in Example 2;

[0029] Figure 4 The current density versus voltage curve of the perovskite solar cell provided in Example 2;

[0030] Figure 5 A schematic structural diagram of the perovskite solar cell provided in Example 3;

[0031] Figure 6 The current density versus voltage curve of the perovskite solar cell provided in Example 3. Detailed Embodiments

[0032] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] The present invention provides a method for enhancing the performance of perovskite solar cells, comprising the following steps:

[0034] Mix the two-dimensional perovskite single crystal with a reagent having surface coordination effect to induce the formation of a two-dimensional perovskite interface at the three-dimensional perovskite interface.

[0035] In the present invention, the preparation method of the two-dimensional perovskite single crystal is preferably specifically:

[0036] Add the organic salt and the inorganic salt into the acid solution, filter after the first mixing, and then perform the second mixing on the filtered mixed solution under an inert atmosphere, and cool down to obtain the two-dimensional perovskite single crystal.

[0037] In the present invention, the organic salt is preferably FAI (formamidinium iodide, HC(NH2)2I), MAI (methylammonium iodide, CH3NH3I), FACl (formamidinium chloride, HC(NH2)2Cl), MACl (methylammonium chloride, CH3NH3Cl), FABr (formamidinium bromide, HC(NH2)2Br) or MABr (methylammonium bromide, CH3NH3Br), and more preferably FAI. The present invention has no special limitation on the source of the organic salt, and commercially available products well-known to those skilled in the art can be used.

[0038] In the present invention, the inorganic salt is preferably MB2, where M is Pb or Sn, and B is I, Cl, Br or F; more preferably PbI2. The present invention has no special limitation on the source of the inorganic salt, and commercially available products well-known to those skilled in the art can be used.

[0039] In the present invention, the acid solution is preferably hydroiodic acid, concentrated nitric acid or concentrated sulfuric acid, and more preferably hydroiodic acid. The present invention has no special limitation on the source of the acid solution, and commercially available products well-known to those skilled in the art can be used.

[0040] In the present invention, the dosage ratio of the organic salt, the inorganic salt and the acid solution is preferably 0.001 mol: 0.001 mol: (2 ml - 20 ml).

[0041] In the present invention, the temperature of the first mixing is preferably 40°C - 60°C, more preferably 50°C, the time is preferably 20 min - 40 min, and more preferably 30 min.

[0042] In the present invention, the inert atmosphere is preferably N2 atmosphere; the temperature of the second mixing is preferably 80°C - 100°C, more preferably 90°C, the time is preferably 1 h - 3 h, and more preferably 2 h.

[0043] In the present invention, the process of cooling down is preferably specifically:

[0044] Cool down to 40°C - 60°C at a rate of 1°C - 3°C per hour to obtain the two-dimensional perovskite single crystal;

[0045] More preferably:

[0046] Cool it to 50 °C at a rate of 2 °C per hour to obtain a two-dimensional perovskite single crystal; then stop heating and wait for it to cool to room temperature for further use.

[0047] In the present invention, the reagent having a surface coordination effect can form a surface coordination with perovskite and can cause an offset in the electronegativity of perovskite, achieving the beneficial effects of enhanced surface stability and increased chemical stability; the reagent having a surface coordination effect is preferably tyramine hydrochloride or ascorbic acid. The present invention has no special restrictions on the source of the reagent having a surface coordination effect, and commercially available products well-known to those skilled in the art can be used.

[0048] In the present invention, the mass ratio of the two-dimensional perovskite single crystal to the reagent having a surface coordination effect is preferably 1:(0.1 - 2), more preferably 1:(0.3 - 1).

[0049] In the present invention, the two-dimensional perovskite single crystal and the reagent having a surface coordination effect are mixed to obtain a two-dimensional perovskite solution; the present invention has no special restrictions on the mixing process, and it is only necessary to achieve uniform stirring.

[0050] The obtained two-dimensional perovskite solution after mixing is used to induce the formation of a two-dimensional perovskite interface at the three-dimensional perovskite interface. In the present invention, the difference between two-dimensional and three-dimensional is the difference in their sizes. Three-dimensional is a significant continuous film, and two-dimensional is a discontinuous state.

[0051] In the present invention, the two-dimensional perovskite interface preferably exists in:

[0052] Between the three-dimensional perovskite interface and the electron transport layer;

[0053] Or: between the three-dimensional perovskite interface and the hole transport layer;

[0054] Or: simultaneously between the three-dimensional perovskite interface and the electron transport layer and between the three-dimensional perovskite interface and the hole transport layer.

[0055] In a preferred embodiment of the present invention, the two-dimensional perovskite interface exists in: between the three-dimensional perovskite interface and the electron transport layer; on this basis, the structure of the perovskite solar cell formed is as follows:

[0056] Transparent conductive substrate - Charge transport layer 1 (electron transport layer) - Two-dimensional perovskite modification layer - Three-dimensional perovskite active layer - Charge transport layer 2 (hole transport layer) - Counter electrode.

[0057] In another preferred embodiment of the present invention, the two-dimensional perovskite interface exists between the three-dimensional perovskite interface and the hole transport layer; on this basis, the perovskite solar cell structure formed is as follows:

[0058] Transparent conductive substrate - Charge transport layer 1 (electron transport layer) - Three-dimensional perovskite active layer - Two-dimensional perovskite modification layer - Charge transport layer 2 (hole transport layer) - Counter electrode.

[0059] In another preferred embodiment of the present invention, the two-dimensional perovskite interface exists between the three-dimensional perovskite interface and the electron transport layer and between the three-dimensional perovskite interface and the hole transport layer at the same time; on this basis, the perovskite solar cell structure formed is as follows:

[0060] Transparent conductive substrate - Charge transport layer 1 (electron transport layer) - Two-dimensional perovskite modification layer 1 - Three-dimensional perovskite active layer - Two-dimensional perovskite modification layer 2 - Charge transport layer 2 (hole transport layer) - Counter electrode.

[0061] The present invention has no special limitation on the specific method for inducing the formation of the two-dimensional perovskite interface at the three-dimensional perovskite interface, and the technical solution of preparing a thin film from the above-mentioned two-dimensional perovskite solution well-known to those skilled in the art can be adopted.

[0062] In a preferred embodiment of the present invention, the two-dimensional perovskite solution is evenly spread on the surface of the three-dimensional perovskite active layer / electron transport layer, and after staying for 20 s to 40 s, it is spin-coated into a uniform thin film at a speed of 2000 rpm to 4000 rpm for 20 s to 40 s; then it is placed on a hot stage at 90 °C to 110 °C for annealing for 10 min to 20 min to obtain a perovskite thin film modified with two-dimensional perovskite.

[0063] In the present invention, the transparent conductive substrate can be any common transparent substrate well-known to those skilled in the art, such as ITO glass, FTO glass, AZO glass, conductive PET, etc., and preferably ITO glass.

[0064] In the present invention, the electron transport layer is preferably a SnO2 layer, a TiO2 layer or a C60 and its derivative layer, and more preferably a SnO2 layer; the thickness of the electron transport layer is preferably 10 nm to 100 nm, and more preferably 20 nm to 40 nm.

[0065] In the present invention, the hole transport layer is preferably a Spiro-OMeTAD layer, a NiOx layer or a CuOx layer, and more preferably a Spiro-OMeTAD layer; the thickness of the hole transport layer is preferably 10 nm to 100 nm, and more preferably 40 nm to 60 nm.

[0066] In the present invention, the thickness of the three-dimensional perovskite interface is preferably 100 nm to 700 nm, more preferably 400 nm.

[0067] In the present invention, the thickness of the two-dimensional perovskite interface is preferably 20 nm to 500 nm, more preferably 25 nm to 420 nm.

[0068] The present invention places no special restrictions on the specific preparation process of the perovskite solar cell, and any preparation method well-known to those skilled in the art can be adopted.

[0069] The present invention provides a strategy for enhancing the performance of three-dimensional perovskite solar cells by two-dimensional perovskites, which specifically involves the structural modification and chemical modification of the two-dimensional perovskite in the perovskite absorption layer. Using a two-step method, two-dimensional perovskite modification is first carried out. Based on the chemically modifiable characteristics of the reagent with surface coordination effects, chemical functional groups are introduced to enhance interface modification, thereby making the two-dimensional perovskite controllable. Then, the three-dimensional perovskite interface is further optimized. This can not only demonstrate the role of two-dimensional perovskites in improving stability but also solve the disadvantage of poor electrical properties of two-dimensional perovskites through coordination modification, achieving the effect of enhancing the performance of perovskite solar cells. Moreover, the method for enhancing the performance of perovskite solar cells provided by the present invention is applicable to the surface modification of two-dimensional perovskites on three-dimensional perovskite layers with different components and is applicable to both normal and inverted perovskite cell structures.

[0070] The present invention provides a method for enhancing the performance of perovskite solar cells, which includes the following steps: mixing two-dimensional perovskite single crystals with a reagent having surface coordination effects to induce the formation of a two-dimensional perovskite interface at the three-dimensional perovskite interface. Compared with the prior art, the present invention provides a strategy for enhancing the performance of three-dimensional perovskite solar cells by two-dimensional perovskites. Using a two-step method, two-dimensional perovskite modification is first carried out. Based on the chemically modifiable characteristics of the reagent with surface coordination effects, chemical functional groups are introduced to enhance interface modification, thereby making the two-dimensional perovskite controllable. Then, the three-dimensional perovskite interface is further optimized. This can not only demonstrate the role of two-dimensional perovskites in improving stability but also solve the disadvantage of poor electrical properties of two-dimensional perovskites through coordination modification, achieving the effect of enhancing the performance of perovskite solar cells.

[0071] In addition, the method provided by the present invention has little impact on the existing preparation process of perovskite solar cells, is easy to implement, has mild and controllable conditions, and has a wide application range, showing broad application prospects.

[0072] To further illustrate the present invention, the following examples are provided for detailed description.

[0073] Example 1

[0074] A 1.5 cm × 1.5 cm indium tin oxide (ITO) glass (glass thickness 2 mm, ITO film thickness 100 nm) was cleaned with ethanol, isopropyl alcohol (IPA), and acetone for 30 minutes each, and then dried with a nitrogen gun.

[0075] The stock solution of tin dioxide (SnO2) was diluted with ultrapure water at a volume ratio of 1:5, and stirred well to obtain the SnO2 precursor solution; 50 μL of the SnO2 precursor solution was evenly spread on the surface of the ITO conductive glass, and the parameters of the spin coater were set as: rotation speed 4000 rpm, time 30 s; then it was annealed on a hot plate at 150 °C for 30 min to obtain a SnO2 thin film (30 nm); the above SnO2 thin film was placed in an ultraviolet ozone cleaner for 30 min for subsequent spin coating.

[0076] Preparation of perovskite precursor solution: First, 0.001 mol of formamidinium iodide (FAI: HC(NH2)2I) and 0.001 mol of PbI2 were weighed and placed in 10 ml of hydroiodic acid. It was placed on a heated magnetic stirring hot plate at a temperature of 50 °C and continuously magnetically stirred for 30 minutes, and then filtered. The above mixed solution was put into a flask and stirred well under a N2 atmosphere to mix it, heated to 90 °C, stirred well for 2 h, and then slowly cooled to 50 °C at a rate of 2 °C per hour. Finally, about 400 mg of orange flaky crystals were obtained, the heating was stopped, and after it cooled to room temperature, 200 mg of tyramine hydrochloride with surface modification and chemical stabilization effects was added and stirred evenly to obtain a two-dimensional perovskite (FAPbI3) solution A.

[0077] 6 g of lead iodide (PbI2) and 60 mg of cesium iodide (CsI) were weighed and dissolved in 9 mL of N,N-dimethylformamide (DMF) and 1 mL of dimethyl sulfoxide (DMSO) solution, and heated and stirred at 70 °C to dissolve it completely to obtain a PbI2 precursor solution B; 0.5 ml of solution A was taken and added to the above solution B, and heated and stirred at 70 °C to mix it evenly to obtain solution C; 80 mg of formamidinium hydroiodide (FAI) and 8 mg of methylammonium chloride (MACl) were dissolved in 1 mL of IPA solution and stirred to dissolve it completely to obtain an organic salt solution D.

[0078] 60 μL of solution C was evenly spread on the surface of the annealed SnO2 thin film above, and the parameters of the spin coater were set as: speed 2000 rpm, time 30 s; then it was placed on a hot plate at 75 °C for 1 min to form a coating; then 80 μL of solution D was evenly spread on the coating formed by the above-prepared solution C, and the parameters of the spin coater were set as: speed 3000 rpm, time 30 s; then it was placed on a hot plate at 150 °C for annealing for 15 min to obtain a three-dimensional perovskite thin film (400 nm).

[0079] Take 40 μL of two-dimensional perovskite solution A and evenly spread it on the surface of the above-mentioned three-dimensional perovskite thin film. After staying for 30 s, spin-coat it into a uniform thin film at a speed of 3000 rpm for 30 s; then place it on a hot stage at 100 °C for annealing for 15 min to obtain a perovskite thin film (420 nm) modified with two-dimensional perovskite.

[0080] Weigh 260 mg of lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) and dissolve it in 1 mL of acetonitrile (CAN). After stirring well, obtain the Li-TFSI solution; then weigh 80 mg of 2,2,7,7-tetra[N,N-bis(4-methoxyphenyl)amino]-9,9-spirobifluorene (Spiro-MeOTAD) and dissolve it in 1 mL of chlorobenzene. Stir well until dissolved; then add 30 μL of 4-tert-butylpyridine (TBP) solution and 35 μL of Li-TFSI solution, and stir well to obtain the hole transport layer solution.

[0081] Take 50 μL of the hole transport layer solution and evenly spread it on the surface of the above-mentioned perovskite thin film modified with two-dimensional perovskite. The parameters of the spin coater are set as: speed 3000 rpm, time 30 s, to obtain the hole transport layer (50 nm).

[0082] Transfer the hole transport layer to a thermal evaporation device. When the vacuum reaches 1×10 -5 Pa, start evaporating the electrode (Au) with a thickness of 100 nm; then place it in an oxygen glove box and leave it overnight for oxidation to obtain a perovskite solar cell.

[0083] Comparative Example 1

[0084] Adopt the preparation method provided in Example 1 above, with the difference that: no two-dimensional perovskite modification is carried out to obtain a perovskite solar cell.

[0085] After testing, the performance data of the perovskite solar cells provided in Example 1 and Comparative Example 1 are shown in Table 1.

[0086] Table 1 Performance data of the perovskite solar cells prepared in Example 1 and Comparative Example 1

[0087] Open-circuit voltage (V) Fill factor (%) <![CDATA[Current density (mA cm -2 )]]> Photovoltaic conversion efficiency (%) Example 1 1.06 74.04 24.87 19.29 Comparative Example 1 1.05 66.45 21.39 14.91

[0088] The comparison chart of the current density vs. voltage curves of the perovskite solar cells provided in Example 1 and Comparative Example 1 is shown in Figure 1 as shown; the comparison chart of the photoelectric conversion efficiency data of the perovskite solar cells provided in Example 1 and Comparative Example 1 is shown in Figure 2 as shown.

[0089] Example 2

[0090] A 1.5 cm × 1.5 cm indium tin oxide (ITO) glass (glass thickness 2 mm, ITO film thickness 100 nm) was cleaned with ethanol, isopropyl alcohol (IPA), and acetone for 30 minutes each, and then dried with a nitrogen gun.

[0091] The stock solution of tin dioxide (SnO2) was diluted with ultrapure water at a volume ratio of 1:5 and stirred well to obtain the SnO2 precursor solution; 50 μL of the SnO2 precursor solution was evenly spread on the surface of the ITO conductive glass, and the spin coater parameters were set as: rotation speed 4000 rpm, time 30 s; then it was annealed on a hot plate at 150 °C for 30 min to obtain the SnO2 thin film (30 nm); the above SnO2 thin film was placed in an ultraviolet ozone cleaner for 30 min for subsequent spin coating.

[0092] Preparation of perovskite precursor solution: First, 0.001 mol of formamidinium iodide (FAI: HC(NH2)2I) and 0.001 mol of PbI2 were each weighed and placed in 10 ml of hydroiodic acid. It was placed on a heated magnetic stirring hot plate at a temperature of 50 °C and continuously magnetically stirred for 30 minutes, and then filtered. The above mixed solution was put into a flask and stirred well under a N2 atmosphere to mix, heated to 90 °C, and stirred well for 2 h. Then it was slowly cooled to 50 °C at a rate of 2 °C per hour. Finally, about 400 mg of orange flaky crystals were obtained. Heating was stopped, and after it cooled to room temperature, 150 mg of ascorbic acid with surface modification and chemical stabilization effects was added and stirred evenly to obtain the two-dimensional perovskite (FAPbI3) solution A.

[0093] 50 μL of the two-dimensional perovskite solution A was evenly spread on the surface of the annealed SnO2 thin film above. After staying for 30 s, it was spin-coated into a uniform thin film at a speed of 3000 rpm for 30 s; then it was annealed on a hot plate at 70 °C for 15 min to obtain a perovskite thin film (25 nm) modified with two-dimensional perovskite.

[0094] 6 g of lead iodide (PbI2) and 60 mg of cesium iodide (CsI) were weighed and dissolved in 9 mL of N,N-dimethylformamide (DMF) and 1 mL of dimethyl sulfoxide (DMSO) solution, and heated and stirred at 70 °C to dissolve them completely to obtain the PbI2 precursor solution B; 0.5 ml of solution A was taken and added to the above solution B, and heated and stirred at 70 °C to make it fully uniform to obtain solution C; 80 mg of formamidinium hydroiodide (FAI) and 8 mg of methylammonium chloride (MACl) were dissolved in 1 mL of IPA solution and stirred to dissolve them completely to obtain the organic salt solution D.

[0095] 60 μL of solution C was evenly spread on the surface of the above-mentioned two-dimensional perovskite modified perovskite film, and the parameters of the spreader were set as: speed 2000 rpm, time 30 s; then placed on a 75°C hot stage for 1 min to form a coating; then 80 μL of solution D was evenly spread on the surface of the coating formed by the above-prepared solution C, and the parameters of the spreader were set as: speed 3000 rpm, time 30 s; then placed on a 150°C hot stage for annealing for 15 min to obtain a three-dimensional perovskite film (400 nm).

[0096] 260 mg of lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) was weighed and dissolved in 1 mL of acetonitrile (CAN), and the solution was obtained after sufficient stirring. Then 80 mg of 2,2,7,7-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9-spirobifluorene (Spiro-MeOTAD) was weighed and dissolved in 1 mL of chlorobenzene, and the solution was sufficient stirring to dissolve. Then 30 μL of 4-tert-butylpyridine (TBP) solution and 35 μL of Li-TFSI solution were added, and the solution was sufficient stirring to obtain a hole transport layer solution.

[0097] 50 μL of the hole transport layer solution was evenly spread on the surface of the three-dimensional perovskite film, and the parameters of the coating machine were set as follows: speed 3000 rpm, time 30 s, to obtain a hole transport layer (50 nm).

[0098] The hole transport layer is transferred to the thermal evaporation equipment with a vacuum degree of 1×10 -5 Pa, the electrode (Au) was evaporated to a thickness of 100 nm; it was then placed in an oxygen glove box for one night for oxidation to obtain a perovskite solar cell.

[0099] See the scanning electron microscope images of the three-dimensional perovskite and two-dimensional perovskite structures in Example 2 of the present invention. Figure 3 shown.

[0100] After testing, the performance data of the perovskite solar cell provided in Example 2 are shown in Table 2.

[0101] Table 2 Performance data of perovskite solar cells prepared in Example 2

[0102] Open-circuit voltage (V) Fill factor (%) <![CDATA[Current density (mA cm -2 )]]> Photovoltaic conversion efficiency (%) Example 2 1.04 71.67 25.51 18.95

[0103] The current density versus voltage curve of the perovskite solar cell provided in Example 2 is shown in Figure 4 shown.

[0104] Example 3

[0105] A 1.5 cm × 1.5 cm indium tin oxide (ITO) glass (glass thickness 2 mm, ITO film thickness 100 nm) was cleaned with ethanol, isopropyl alcohol (IPA), and acetone for 30 minutes each, and then dried with a nitrogen gun.

[0106] The stock solution of tin dioxide (SnO2) was diluted with ultrapure water at a volume ratio of 1:5, and stirred well to obtain the SnO2 precursor solution; 50 μL of the SnO2 precursor solution was evenly spread on the surface of the ITO conductive glass, and the parameters of the spin coater were set as follows: rotation speed 4000 rpm, time 30 s; then it was annealed on a hot plate at 150 °C for 30 min to obtain the SnO2 thin film (30 nm); the above SnO2 thin film was placed in an ultraviolet ozone cleaner for 30 min for subsequent spin coating.

[0107] Preparation of perovskite precursor solution: First, 0.001 mol of formamidinium iodide (FAI: HC(NH2)2I) and 0.001 mol of PbI2 were weighed into 10 ml of hydroiodic acid, and placed on a heated magnetic stirring hot plate at a temperature of 50 °C, and continuously magnetically stirred for 30 minutes, then filtered. The above mixed solution was put into a flask, and stirred well under a N2 atmosphere to mix them, heated to 90 °C, stirred well for 2 h, and then slowly cooled to 50 °C at a rate of 2 °C per hour. Finally, about 400 mg of orange flaky crystals were obtained, the heating was stopped, and after it cooled to room temperature, 150 mg of ascorbic acid with surface modification and chemical stabilization effects was added and stirred evenly to obtain the two-dimensional perovskite (FAPbI3) solution A;

[0108] Preparation of perovskite precursor solution: First, 0.001 mol of formamidinium bromide (FABr: HC(NH2)2Br) and 0.001 mol of PbI2 were weighed into 10 ml of hydroiodic acid, and placed on a heated magnetic stirring hot plate at a temperature of 50 °C, and continuously magnetically stirred for 30 minutes, then filtered. The above mixed solution was put into a flask, and stirred well under a N2 atmosphere to mix them, heated to 90 °C, stirred well for 2 h, and then slowly cooled to 50 °C at a rate of 2 °C per hour. Finally, about 400 mg of orange flaky crystals were obtained, the heating was stopped, and after it cooled to room temperature, 200 mg of tyramine hydrochloride with surface modification and chemical stabilization effects was added and stirred evenly to obtain the two-dimensional perovskite (FAPbI2Br) solution A'.

[0109] Weigh 6 g of lead iodide (PbI2) and 60 mg of cesium iodide (CsI), dissolve them in a solution of 9 mL of N,N-dimethylformamide (DMF) and 1 mL of dimethyl sulfoxide (DMSO), heat and stir at 70 °C until completely dissolved to obtain the PbI2 precursor solution B; take 0.5 mL of solution A, add it to the above solution B, heat and stir at 70 °C until thoroughly homogeneous to obtain solution C; dissolve 80 mg of formamidinium hydroiodide (FAI) and 8 mg of methylammonium chloride (MACl) in 1 mL of IPA solution, stir until completely dissolved to obtain the organic salt solution D.

[0110] Take 50 μL of the two-dimensional perovskite solution A and evenly spread it on the surface of the annealed SnO2 film mentioned above. After staying for 30 s, spin-coat it into a uniform film at a speed of 3000 rpm for 30 s; then place it on a hot stage at 70 °C for annealing for 15 min to obtain the perovskite film 1 (25 nm) modified with two-dimensional perovskite.

[0111] Take 60 μL of solution C and evenly spread it on the surface of the perovskite film 1 modified with two-dimensional perovskite mentioned above. The parameters of the spin coater are set as: speed 2000 rpm, time 30 s; then place it on a hot stage at 75 °C for 1 min to form a coating; then take 80 μL of solution D and evenly spread it on the surface of the coating formed by the above-prepared solution C. The parameters of the spin coater are set as: speed 3000 rpm, time 30 s; then place it on a hot stage at 150 °C for annealing for 15 min to obtain the three-dimensional perovskite film (400 nm).

[0112] Take 40 μL of the two-dimensional perovskite solution A' and evenly spread it on the surface of the above three-dimensional perovskite film. After staying for 30 s, spin-coat it into a uniform film at a speed of 3000 rpm for 30 s; then place it on a hot stage at 100 °C for annealing for 15 min to obtain the perovskite film 2 (25 nm) modified with two-dimensional perovskite.

[0113] Weigh 260 mg of lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) and dissolve it in 1 mL of acetonitrile (CAN), stir thoroughly to obtain the Li-TFSI solution; then weigh 80 mg of 2,2,7,7-tetra[N,N-bis(4-methoxyphenyl)amino]-9,9-spirobifluorene (Spiro-MeOTAD) and dissolve it in 1 mL of chlorobenzene, stir until dissolved; then add 30 μL of 4-tert-butylpyridine (TBP) solution and 35 μL of Li-TFSI solution, stir thoroughly to obtain the hole transport layer solution.

[0114] Take 50 μL of the hole transport layer solution and evenly spread it on the surface of the perovskite film 2 modified with two-dimensional perovskite mentioned above. The parameters of the spin coater are set as: speed 3000 rpm, time 30 s, to obtain the hole transport layer (50 nm).

[0115] Transfer the hole transport layer into the thermal evaporation equipment. When the vacuum degree reaches 1×10 -5 Pa, start evaporating the electrode (Au) with a thickness of 100 nm; then place it in an oxygen glove box overnight for oxidation to obtain a perovskite solar cell; see the structural schematic diagram of the perovskite solar cell provided in Example 3 in Figure 5 shown.

[0116] After testing, see the various performance data of the perovskite solar cell provided in Example 3 in Table 2.

[0117] Table 3 Various performance data of the perovskite solar cell prepared in Example 3

[0118] Open-circuit voltage (V) Fill factor (%) <![CDATA[Current density (mA cm -2 )]]> Photovoltaic conversion efficiency (%) Example 3 1.07 72.67 25.73 20.07

[0119] See the current density vs. voltage curve of the perovskite solar cell provided in Example 3 in Figure 6 shown.

[0120] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for enhancing the performance of perovskite solar cells, characterized in that, It includes the following steps: Mix the two-dimensional perovskite single crystal with a reagent having surface coordination effect to induce the formation of a two-dimensional perovskite interface at the three-dimensional perovskite interface; The specific preparation method of the two-dimensional perovskite single crystal is as follows: Add the organic salt and the inorganic salt into the acid solution, filter after the first mixing, and then perform the second mixing on the filtered mixed solution under an inert atmosphere, and cool down to obtain the two-dimensional perovskite single crystal; The organic salt is FAI, MAI, FACl, MACl, FABr or MABr; The inorganic salt is MB2, where M is Pb or Sn, and B is I, Cl, Br or F; The acid solution is hydroiodic acid, concentrated nitric acid or concentrated sulfuric acid; The temperature of the first mixing is 40°C to 60°C, and the time is 20 min to 40 min; the inert atmosphere is N2 atmosphere; the temperature of the second mixing is 80°C to 100°C, and the time is 1 h to 3 h; The specific process of the cooling is as follows: Cool down to 40°C to 60°C at a rate of 1°C to 3°C per hour to obtain the two-dimensional perovskite single crystal; The reagent having surface coordination effect is tyramine hydrochloride or ascorbic acid.

2. The method for enhancing the performance of a perovskite solar cell according to claim 1, wherein The mass ratio of the two-dimensional perovskite single crystal to the reagent having surface coordination effect is 1:(0.1 to 2).

3. The method for enhancing the performance of a perovskite solar cell according to claim 1, wherein The two-dimensional perovskite interface exists in: Between the three-dimensional perovskite interface and the electron transport layer; Or: between the three-dimensional perovskite interface and the hole transport layer; Or: simultaneously exist between the three-dimensional perovskite interface and the electron transport layer and between the three-dimensional perovskite interface and the hole transport layer.

4. The method for enhancing the performance of a perovskite solar cell according to claim 3, wherein The electron transport layer is a SnO2 layer, a TiO2 layer or a C60 and its derivative layer, and the thickness is 10 nm to 100 nm; The hole transport layer is a Spiro-OMeTAD layer, a NiOx layer or a CuOx layer, and the thickness is 10 nm to 100 nm.

5. The method for enhancing the performance of a perovskite solar cell according to claim 1, wherein The thickness of the three-dimensional perovskite interface is 100 nm to 700 nm.

6. The method for enhancing the performance of a perovskite solar cell according to claim 1, wherein The thickness of the two-dimensional perovskite interface is 20 nm to 500 nm.

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