Epitaxial growth template, tin-based perovskite thin film, tin-based perovskite solar cell

Abstract

The application discloses an epitaxial growth template, a tin-based perovskite thin film and a tin-based perovskite solar cell, and belongs to the technical field of perovskite solar cells. The epitaxial growth template is prepared by the following method: stannous iodide, stannous fluoride, an organic ammonium salt containing a conjugated aromatic ring and tin powder are dissolved in a solvent, then the precursor solution is obtained by stirring for a period of time; the precursor solution is uniformly coated, then annealing is performed to obtain the epitaxial growth template. In view of the fast crystallization kinetics and disordered crystal orientation of the tin-based perovskite thin film, the epitaxial growth template is used to induce three-dimensional perovskite epitaxial growth, the crystallization rate of the tin-based perovskite is delayed, the (100) crystal face growth of the tin-based perovskite is promoted, the in-grain defect state density is minimized, uniform tin-based perovskite thin films are formed in a larger range, and finally the photoelectric conversion efficiency of the tin-based perovskite solar cell is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of perovskite solar cells, and particularly relates to an epitaxial growth template, a tin-based perovskite thin film and a tin-based perovskite solar cell. BACKGROUND

[0002] Organic-inorganic hybrid perovskite solar cells have been developed vigorously due to their excellent optoelectronic properties. However, the biological toxicity associated with lead poses potential hazards to the environment and human health. As a candidate material, tin-based perovskite, which has less toxicity, becomes the most promising material due to its excellent optoelectronic properties and more suitable optical band gap compared with lead-based perovskite.

[0003] However, compared with the inert 6s electron pair of Pb 2+ , Sn 2+ has two active 5s electrons, which makes it have stronger Lewis acidity, resulting in a relatively fast crystallization rate of tin-based perovskite. This uncontrollable crystallization process leads to disordered crystal orientation and a significant increase in defect states. These defects are both charge recombination centers and degradation sites, which seriously hinder the improvement of the efficiency and stability of tin-based perovskite solar cells.

[0004] Inspired by the orientation modulation of lead-based perovskite, a large number of additives have been used to alleviate the orientation disorder caused by fast crystallization. However, the residual additives and intermediate phases will reduce the phase purity and have an adverse effect on the device performance, and the modulation ability and universality of single additive are limited. Epitaxial growth has been proved to be an effective strategy to regulate the crystallization kinetics of thin films in lead-based perovskite, which can produce highly oriented thin films with low defect density. However, the traditional epitaxial growth strategy based on PEA2SnI4 is not significant in delaying the crystallization rate and promoting the preferred orientation.

[0005] Therefore, it is the key to improve the performance of tin-based perovskite solar cells to develop a simple epitaxial growth strategy suitable for the preparation of tin-based perovskite solar cells, which can regulate the crystallization of perovskite along the preferred orientation to minimize the trap state density. SUMMARY

[0006] In order to solve the problems of fast crystallization kinetics and disordered crystal orientation of tin-based perovskite thin film proposed in the background art, the purpose of the present application is to provide an epitaxial growth template, a tin-based perovskite thin film and a tin-based perovskite solar cell. The present application develops an epitaxial growth template, which is used as a two-dimensional template to induce the epitaxial growth of three-dimensional perovskite, effectively delays the crystallization rate of tin-based perovskite and promotes the preferred (100) plane growth, thereby minimizing the in-body defect state density, ensuring the formation of uniform tin-based perovskite thin film in a larger range, and finally improving the photoelectric conversion efficiency and stability of tin-based perovskite solar cells.

[0007] To achieve the above object, the technical scheme adopted by the present application is as follows: on the one hand, the present application provides an epitaxial growth template prepared by the following method:

[0008] SnI2, SnF2, an organic ammonium salt containing a conjugated aromatic ring and Sn powder are dissolved in a solvent, and then stirred for a period of time to obtain a precursor solution;

[0009] The precursor solution is uniformly coated, and then annealed to obtain an epitaxial growth template.

[0010] The organic ammonium salt containing a conjugated aromatic ring and SnI2 can form a low-dimensional perovskite, and the organic ammonium salt with enhanced π conjugation can make the low-dimensional perovskite orderly arranged, the conversion of the low-dimensional perovskite to three-dimensional perovskite which is thermodynamically stable can slow down the growth rate of the crystal, thereby inducing the slow and orderly epitaxial growth of three-dimensional perovskite. In addition, the organic ammonium salt containing a conjugated aromatic ring can also induce the orientation of perovskite by reducing the surface energy of the crystal.

[0011] Further, the organic ammonium salt containing a conjugated aromatic ring is selected from at least one of 2-(naphthalene-2-yl)ethylamine hydroiodide (NEAI), 1-naphthylmethyl amine iodide and 2-naphthylmethyl amine iodide;

[0012] The solvent is selected from at least one of N, N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

[0013] Further, the molar ratio of SnI2, SnF2, the organic ammonium salt containing a conjugated aromatic ring and Sn powder is 1:(0.05-0.2):(0.01-0.1):(0.01-0.2);

[0014] The ratio of the amount of the organic ammonium salt containing a conjugated aromatic ring to the solvent is (0.02mol-0.06mol):1mL.

[0015] Further, the stirring time is 2h-12h;

[0016] The coating is spin coating, the rotation speed of the spin coating is 5000rpm-7000rpm, and the time of the spin coating is 20s-40s;

[0017] The annealing temperature is 40℃-100℃, and the annealing time is 1min-10min.

[0018] Further, the precursor solution needs to be filtered before use.

[0019] Further, the purity of the organic ammonium salt containing a conjugated aromatic ring is above 97%.

[0020] In another aspect, the present application provides a tin-based perovskite thin film prepared by the following method:

[0021] Formamidinium iodide (FAI), ethylammonium iodide (EAI) and ethylenediamine dihydroiodide (EDAI2) are dissolved in a solvent to obtain a cation solution;

[0022] The cation solution is uniformly coated on the epitaxial growth template described in any of the above, and then annealed to obtain a tin-based perovskite thin film.

[0023] Further, the molar ratio of formamidinium iodide (FAI), ethylammonium iodide (EAI) and ethylenediamine dihydroiodide (EDAI2) is 1:(0.1-0.4):(0.01-0.05);

[0024] The solvent is selected from formic acid (FA) or isopropyl alcohol (IPA).

[0025] Further, the coating is spin coating, the rotation speed of the spin coating is 5000 rpm-7000 rpm, and the time of the spin coating is 20 s-40 s;

[0026] The annealing temperature is 40℃-100℃, and the annealing time is 5 min-20 min.

[0027] In another aspect, the present application provides a tin-based perovskite solar cell, which comprises a transparent conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, a hole blocking layer, and a cathode electrode, which are sequentially stacked from bottom to top.

[0028] The perovskite light-absorbing layer is the tin-based perovskite thin film described in any of the above.

[0029] Further, the transparent conductive substrate is selected from ITO conductive glass or FTO conductive glass;

[0030] The material used for the hole transport layer is poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS);

[0031] The material used for the electron transport layer includes at least one of fullerene (C60) and fullerene derivatives, and the fullerene derivatives include indenodithione-C 60 bis-adduct (ICBA), [6,6]-phenyl-C 61 - methyl isobutyl phthalate (PCBM);

[0032] The material used for the hole blocking layer includes one of bathocuproine (BCP) and polyethyleneimine (PEI).

[0033] The cathode electrode comprises a silver (Ag) electrode.

[0034] Further, the thickness of the hole transport layer is 30-40 nm, the thickness of the perovskite light-absorbing layer is 200-400 nm, the thickness of the electron transport layer is 30-40 nm, the thickness of the hole blocking layer is 8-10 nm, and the thickness of the cathode electrode is 100-110 nm.

[0035] In another aspect, the application provides a preparation method of a tin-based perovskite solar cell, comprising the following steps:

[0036] (1) pretreating a transparent conductive substrate;

[0037] (2) coating a solution of materials for a hole transport layer on the pretreated transparent conductive substrate obtained in step (1), and then performing annealing to obtain a hole transport layer;

[0038] (3) dissolving stannous iodide (SnI2), stannous fluoride (SnF2), an organic ammonium salt containing a conjugated aromatic ring, and tin powder in a solvent, and then stirring for a period of time to obtain a precursor solution; filtering and uniformly coating the precursor solution on the hole transport layer, and then performing annealing to obtain an epitaxial growth template; dissolving formamidinium hydriodide (FAI), ethylamine hydriodide (EAI), and ethylenediamine dihydriodide (EDAI2) in a solvent to obtain a cation solution; uniformly coating the cation solution on the epitaxial growth template, and then performing annealing to obtain a tin-based perovskite thin film;

[0039] (4) preparing a solution of materials for an electron transport layer, coating the solution of materials for the electron transport layer on the tin-based perovskite thin film prepared in step (3), and then performing annealing to obtain an electron transport layer;

[0040] (5) preparing a solution of materials for a hole blocking layer, coating the solution of materials for the hole blocking layer on the electron transport layer prepared in step (4) to obtain a hole blocking layer;

[0041] (6) preparing a cathode electrode on the hole blocking layer by using a vacuum evaporation technology to obtain a tin-based perovskite solar cell.

[0042] Further, in step (2), the coating is spin coating, the rotation speed of the spin coating is 6000-8000 rpm, the time of the spin coating is 30-60 s, the annealing temperature is 130-150℃, and the annealing time is 10-30 min.

[0043] Further, the coating of the precursor solution in step (3) is spin coating, the rotation speed of the spin coating is 5000 rpm-7000 rpm, the time of the spin coating is 20 s-40 s; the temperature of the annealing is 40 DEG C-100 DEG C, the time of the annealing is 1 min-10 min.

[0044] The coating of the cation solution in step (3) is spin coating, the rotation speed of the spin coating is 5000 rpm-7000 rpm, the time of the spin coating is 20 s-40 s; the temperature of the annealing is 40 DEG C-100 DEG C, the time of the annealing is 5 min-20 min.

[0045] Further, the coating in step (4) is spin coating, the rotation speed of the spin coating is 1000 rpm-3000 rpm, the time of the spin coating is 20 s-40 s, the temperature of the annealing is 40 DEG C-100 DEG C, the time of the annealing is 5 min-30 min.

[0046] Further, the coating in step (5) is spin coating, the rotation speed of the spin coating is 3000 rpm-5000 rpm, the time of the spin coating is 20 s-40 s.

[0047] Principle of the application: by introducing the organic ammonium salt containing conjugated aromatic ring to react with SnI2, A2SnI4 (A is the organic ammonium cation containing conjugated aromatic ring) two-dimensional template is generated in advance. Based on the epitaxial growth theory, this ordered two-dimensional perovskite template plays a key role in the preferred orientation of the three-dimensional perovskite formed subsequently. On the one hand, the three-dimensional perovskite grown based on the A2SnI4 template inherits the directional arrangement characteristics of the two-dimensional crystal, reduces the lattice orientation mismatch, thereby forming a tin-based perovskite with (100) crystal plane preferred orientation. In addition, according to the Wulff construction theory, AI (A is the organic ammonium cation containing conjugated aromatic ring) can also induce the orientation of perovskite by reducing the surface energy of the crystal. On the other hand, A2SnI4 is further converted into two-dimensional perovskite with different n values after the participation of FAI in the reaction, and finally undergoes a non-spontaneous thermodynamic process to convert into FASnI3. This conversion process significantly slows down the crystal growth rate, thereby achieving a significant reduction in the defect state density.

[0048] Compared with the prior art, the application has the following beneficial effects:

[0049] (1) The application develops a simple epitaxial growth strategy to regulate the crystallization kinetics of tin-based perovskite, and for the first time uses A2SnI4 generated by the reaction of organic ammonium salt containing conjugated aromatic ring and SnI2 as a template for three-dimensional tin-based perovskite epitaxial growth. The organic ammonium salt with enhanced π conjugation successfully replaces the traditional 2-phenylethylamine hydroiodide (PEAI), realizes the ordered arrangement of three-dimensional perovskite, not only optimizes the carrier transport kinetics, but also ensures the formation of uniform tin-based perovskite film in a large range.

[0050] (2) The tin-based perovskite solar cell provided by the application has high carrier lifetime and low defect state density, and realizes photoelectric conversion efficiencies of 14.03% and 12.44% on effective areas of 0.04cm 2 and 1cm 2 respectively.

[0051] (3) The preparation method involved in the application is relatively simple, convenient to operate, low in energy consumption, universal, and suitable for popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 It is a schematic diagram of the structure of the tin-based perovskite solar cell prepared in Examples 4-7 and Comparative Examples 5 and 6 of the application;

[0053] Figure 2 It is a grazing incidence X-ray diffraction pattern of the tin-based perovskite film prepared in Example 2 and Comparative Examples 1 and 2 of the application;

[0054] Figure 3 It is a time-resolved photoluminescence pattern of the tin-based perovskite film prepared in Example 2 and Comparative Examples 1 and 2 of the application;

[0055] Figure 4 It is a schematic diagram of the selected position for grazing incidence X-ray diffraction testing of Example 3 and Comparative Examples 3 and 4 of the application;

[0056] Figure 5 It is a grazing incidence X-ray diffraction pattern of the tin-based perovskite film prepared in Example 3 and Comparative Examples 3 and 4 of the application;

[0057] Figure 6 It is an electrochemical impedance spectrum of the tin-based perovskite solar cell prepared in Examples 4-6 and Comparative Examples 5 and 6 of the application;

[0058] Figure 7 It is a current-voltage characteristic curve diagram of the tin-based perovskite solar cell prepared in Example 5 and Comparative Examples 5 and 6 of the application;

[0059] Figure 8The current-voltage characteristic curve of the tin-based perovskite solar cell prepared in Embodiment 7 of the present application is shown in the following figure. DETAILED DESCRIPTION

[0060] The specific embodiments of the present application are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present application, and are not intended to limit the present application.

[0061] Unless defined, the technical terms used in the following examples have the same meanings as generally understood by those skilled in the art to which the present application pertains. The test reagents used in the following examples are all conventional biochemical reagents unless otherwise specified; and the experimental methods used are all conventional methods unless otherwise specified.

[0062] Embodiment 1

[0063] Preparation of the epitaxial growth template:

[0064] (1) A 1.5 cm x 1.5 cm etched ITO conductive glass substrate was sequentially cleaned by ultrasonic treatment in a water solution of detergent, acetone, deionized water and isopropanol for 15 min each. Then it was blown dry with N2 and placed in a plasma cleaner to treat the ITO substrate with UV-ozone for 10 min.

[0065] (2) Stannous iodide (SnI2), stannous fluoride (SnF2), 2-(naphthalen-2-yl)ethylamine hydroiodide (NEAI) and tin (Sn) powder were dissolved in N,N-dimethylformamide (DMF) at a molar ratio of 1:0.1:0.05:0.05, and then stirred for 4 h to obtain a precursor solution. The precursor solution was filtered and spin-coated (at a speed of 7000 rpm for 30 s) on the pretreated ITO conductive glass, and then annealed (at a temperature of 70°C for 1 min) to obtain an epitaxial growth template.

[0066] Embodiment 2

[0067] Preparation of the tin-based perovskite thin film: (1) A 1.5 cm x 1.5 cm etched ITO conductive glass substrate was sequentially cleaned by ultrasonic treatment in a water solution of detergent, acetone, deionized water and isopropanol for 15 min each. Then it was blown dry with N2 and placed in a plasma cleaner to treat the ITO substrate with UV-ozone for 10 min.

[0068] (2) Stannous iodide (SnI2), stannous fluoride (SnF2), 2-(naphthalen-2-yl)ethylamine hydroiodide (NEAI) and tin (Sn) powder were dissolved in N,N-dimethylformamide (DMF) with a molar ratio of 1:0.1:0.05:0.05, and then stirred for 4 h to obtain a precursor solution; meanwhile, formamidinium iodide (FAI), ethylamine hydroiodide (EAI) and ethylenediamine dihydroiodide (EDAI2) were dissolved in formic acid (FA) with a molar ratio of 1:0.25:0.01 to obtain a cation solution, which was ready for use. The 2-(naphthalen-2-yl)ethylamine hydroiodide (NEAI) has a molecular structure shown in formula (1):

[0069]

[0070] (3) The precursor solution prepared in step (2) was filtered and spin-coated (at a speed of 7000 rpm for 30 s) on the pre-processed ITO conductive glass, and then annealed (at a temperature of 70 °C for 1 min) to obtain an epitaxial growth template.

[0071] (4) The cation solution prepared in step (2) was spin-coated (at a speed of 7000 rpm for 30 s) on the surface of the epitaxial growth template, and then annealed (at a temperature of 70 °C for 10 min) to obtain a 250 nm tin-based perovskite thin film.

[0072] Example 3

[0073] The preparation method in Example 3 is generally the same as that in Example 2. The difference is that the ITO conductive glass in step (1) is changed from 1.5 cm x 1.5 cm to 2.5 cm x 2.5 cm.

[0074] Example 4

[0075] The tin-based perovskite solar cell comprises, from bottom to top, a transparent conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, a hole blocking layer, and a cathode electrode, which are sequentially stacked. The perovskite light-absorbing layer is a tin-based perovskite thin film. The transparent conductive substrate is selected from ITO conductive glass. The material for the hole transport layer is poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid). The material for the electron transport layer is ICBA. The material for the hole blocking layer is BCP. The cathode electrode is a silver electrode.

[0076] Preparation of the tin-based perovskite solar cell:

[0077] (1) Transparent conductive substrate pretreatment: 1.5 cm x 1.5 cm etched ITO conductive glass substrate was sequentially cleaned in a water solution of detergent, acetone, deionized water and isopropanol by ultrasonic treatment for 15 min. Then dry with N2, and place in a plasma cleaner to treat the ITO substrate with UV-ozone for 10 min.

[0078] (2) Preparation of hole transport layer:

[0079] Preparation of hole transport layer: Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) solution (PEDOT:PSS) was filtered and spin-coated (rotation speed of 6000 rpm, time of 60 s) on the pretreated ITO conductive glass, and then annealed (annealing temperature of 140 °C, time of 20 min) to obtain a 30 nm PEDOT:PSS layer.

[0080] (3) Preparation of perovskite light-absorbing layer:

[0081] Preparation of precursor solution: Stannous iodide (SnI2), stannous fluoride (SnF2), 2-(naphthalen-2-yl)ethylamine hydroiodide (NEAI) and tin (Sn) powder were dissolved in N,N-dimethylformamide (DMF) according to a molar ratio of 1:0.1:0.025:0.05, and then stirred for 4 h to obtain a precursor solution for standby.

[0082] Preparation of cation solution: Formamidinium iodide (FAI), ethylamine hydroiodide (EAI) and ethylenediamine dihydroiodide (EDAI2) were dissolved in formic acid (FA) according to a molar ratio of 1:0.25:0.01 to obtain a cation solution for standby.

[0083] Preparation of epitaxial growth template: The precursor solution was filtered and spin-coated (rotation speed of 7000 rpm, time of 30 s) on the surface of the PEDOT:PSS layer, and then annealed (annealing temperature of 70 °C, time of 1 min) to obtain an epitaxial growth template.

[0084] Preparation of tin-based perovskite thin film: The cation solution was spin-coated (rotation speed of 7000 rpm, time of 30 s) on the surface of the epitaxial growth template, and then annealed (annealing temperature of 70 °C, time of 10 min) to obtain a 250 nm tin-based perovskite thin film.

[0085] (4) Preparation of electron transport layer:

[0086] Preparation of transport layer solution: 18 mg of ICBA powder was dissolved in 1 mL of chlorobenzene to obtain an ICBA solution.

[0087] Preparation of the electron transport layer: ICBA solution was spin-coated (rotation speed was 1200 rpm, time was 30 s) on the surface of the tin-based perovskite thin film, and then annealing (annealing temperature was 70 °C, time was 10 min) was performed to obtain a 30 nm ICBA layer.

[0088] (5) Preparation of the hole blocking layer:

[0089] Preparation of the blocking layer solution: 0.5 mg of BCP was dissolved in 1 mL of isopropanol to prepare a BCP solution.

[0090] Preparation of the hole blocking layer: the BCP solution was spin-coated (rotation speed was 4500 rpm, time was 30 s) on the surface of the electron transport layer to obtain an 8 nm hole blocking layer.

[0091] (6) Evaporation of the metal electrode: the product obtained in step (5) was placed in an evaporation instrument, and Ag was evaporated on the surface of the hole blocking layer under high vacuum to obtain a 100 nm metal electrode Ag.

[0092] Example 5

[0093] The preparation method in Example 5 was generally the same as that in Example 4. The difference was that the molar ratio in the precursor solution in step (3) was changed to SnI2: SnF2: NEAI: Sn powder = 1: 0.1: 0.05: 0.05.

[0094] Example 6

[0095] The preparation method in Example 6 was generally the same as that in Example 4. The difference was that the molar ratio in the precursor solution in step (3) was changed to SnI2: SnF2: NEAI: Sn powder = 1: 0.1: 0.075: 0.05.

[0096] Example 7

[0097] The preparation method in Example 7 was generally the same as that in Example 5. The difference was that the ITO conductive glass in step (1) was changed from 1.5 cm x 1.5 cm to 2.5 cm x 2.5 cm.

[0098] The tin-based perovskite solar cells prepared in Examples 4-7 had the structure as shown in Figure 1 .

[0099] Comparative Example 1

[0100] The preparation method in Comparative Example 1 was generally the same as that in Example 2. The difference was that NEAI was not added in the precursor solution in step (2), i.e., the composition of the precursor solution was SnI2: SnF2: Sn powder = 1: 0.1: 0.05.

[0101] Comparative Example 2

[0102] The preparation method in Comparative Example 2 is generally the same as that in Example 2. The difference is that NEAI in the precursor solution in step (2) is replaced by PEAI, i.e., the composition of the precursor solution containing SnI2 is SnI2: SnF2: PEAI: Sn powder = 1:0.1:0.05:0.05. PEAI has a molecular structure shown in formula (2):

[0103]

[0104] The tin-based perovskite films prepared in Example 2 and Comparative Examples 1 and 2 were subjected to grazing incidence X-ray diffraction and time-resolved photoluminescence tests, and the results are shown in Figure 2 , Figure 3 From Figure 2 , it can be seen that the (100) crystallinity of the tin-based perovskite film prepared based on the epitaxial growth template is greatly improved, and from Figure 3 , it can be seen that the carrier lifetime of the tin-based perovskite film prepared based on the epitaxial growth template is increased. The above results prove that the quality of the tin-based perovskite film prepared based on the epitaxial growth template is significantly improved.

[0105] Comparative Example 3

[0106] The preparation method in Comparative Example 3 is generally the same as that in Example 3. The difference is that NEAI is not added to the precursor solution in step (2), i.e., the composition of the precursor solution containing SnI2 is SnI2: SnF2: Sn powder = 1:0.1:0.05.

[0107] Comparative Example 4

[0108] The preparation method in Comparative Example 4 is generally the same as that in Example 3. The difference is that NEAI in the precursor solution in step (2) is replaced by PEAI, i.e., the composition of the precursor solution containing SnI2 is SnI2: SnF2: PEAI: Sn powder = 1:0.1:0.05:0.05.

[0109] The tin-based perovskite films prepared in Example 3 and Comparative Examples 3 and 4 were subjected to grazing incidence X-ray diffraction tests at 16 different positions as shown in Figure 4 , and the results are shown in Figure 5 . From Figure 5 , it can be seen that, compared with other tin-based perovskite films, the tin-based perovskite film prepared based on the epitaxial growth template exhibits a stronger and more uniform (100) diffraction peak, and there is no SnI2 diffraction peak, which indicates that the overall quality of the tin-based perovskite film is uniformly improved.

[0110] Comparative Example 5

[0111] The preparation method in Comparative Example 5 is generally the same as that in Example 5. The difference is that no NEAI is added in the precursor solution in step (3), i.e. the composition of the precursor solution is SnI2: SnF2: Sn powder = 1: 0.1: 0.05.

[0112] Comparative Example 6

[0113] The preparation method in Comparative Example 6 is generally the same as that in Example 5. The difference is that the NEAI in the precursor solution in step (3) is replaced by PEAI, i.e. the composition of the precursor solution is SnI2: SnF2: PEAI: Sn powder = 1: 0.1: 0.05: 0.05.

[0114] The tin-based perovskite solar cells prepared in Comparative Examples 5-6 have the structure as shown in Figure 1 .

[0115] The tin-based perovskite solar cells prepared in Examples 4-6 and Comparative Examples 5, 6 are subjected to electrochemical impedance test, and the results are shown in Figure 6 . As can be seen from Figure 6 , the tin-based perovskite solar cells prepared based on the epitaxial growth template have a larger recombination resistance and have better charge transport performance. In addition, it can be seen that the tin-based perovskite solar cell prepared in Example 5 has a larger recombination resistance than that in Example 4 and Example 6, i.e. when SnI2: SnF2: NEAI: Sn powder = 1: 0.1: 0.05: 0.05, the tin-based perovskite solar cell prepared has the best charge transport performance.

[0116] Based on the above analysis, the perovskite solar cells prepared in Example 5 and Comparative Examples 5, 6 are subjected to photoelectric conversion efficiency test. The current-voltage (J-V) performance test is carried out under the conditions of a solar simulator, a standard one sun light (AM 1.5G, 100 mW / cm 2 ), an effective area of 0.04 cm 2 , and a scanning speed of 20 mV / s. The test results are shown in Table 1 and Figure 7 . As can be seen from Table 1 and Figure 7 , the tin-based perovskite solar cell prepared based on the epitaxial growth template has the best performance, and its conversion efficiency can reach 14.03%, which is obviously better than that of Comparative Examples 5, 6.

[0117] Table 1 Performance parameters of tin-based perovskite solar cells

[0118] Open circuit voltage (V) Short circuit current (mA / cm 2 ) Fill factor (%) Conversion efficiency (%) Example 5 0.95 20.64 71.71 14.03 Comparative Example 5 0.77 17.54 68.27 9.27 Comparative Example 6 0.91 19.81 69.32 12.46

[0119] The quality of the tin-based perovskite thin film and the performance of the corresponding solar cell are obviously improved based on the epitaxial growth template, which is due to the fact that the (100) crystallinity of the thin film prepared by this method is greatly improved and the internal defect state density is significantly reduced. In contrast, the photoelectric conversion efficiency of the tin-based perovskite solar cell prepared without adding PEAI or NEAI and based on PEA2SnI4 is at a relatively low level, reflecting the superiority of the preparation method based on the epitaxial growth template.

[0120] The perovskite solar cell prepared in Example 7 was subjected to photoelectric conversion efficiency test, and the current-voltage (J-V) performance test was carried out under the conditions of a solar simulator, a standard one sun light (AM 1.5G, 100 mW / cm 2 ), an effective area of 1.00 cm 2 , and a scanning speed of 20 mV / s. The test results are shown in Figure 8 , and it can be seen from Figure 8 that the conversion efficiency of the tin-based perovskite solar cell prepared based on the epitaxial growth template can reach 12.44%.

[0121] Although the specific embodiments of the present application are described above, those skilled in the art should understand that these are only illustrative, and various changes or modifications can be made to the present embodiments without departing from the principles and essence of the present application, and the protection scope of the present application is only defined by the appended claims.

Claims

1. An epitaxial growth template, characterized in that, It is prepared by the following method: Stannous iodide, stannous fluoride, an organic ammonium salt containing a conjugated aromatic ring, and tin powder are dissolved in a solvent and then stirred for a period of time to obtain a precursor solution. The precursor solution was uniformly coated and then annealed to obtain an epitaxial growth template. The organic ammonium salt containing a conjugated aromatic ring is selected from at least one of 2-(naphthyl-2-yl)ethylamine hydroiodate, 1-naphthylmethylamine iodide, and 2-naphthylmethylamine iodide; The molar ratio of stannous iodide, stannous fluoride, organic ammonium salt containing a conjugated aromatic ring, and tin powder is 1:(0.05~0.2):(0.01~0.1):(0.01~0.2). The stirring time is 2 h to 12 h; The coating is spin coating, the spin coating speed is 5000 rpm to 7000 rpm, and the spin coating time is 20 s to 40 s; The annealing temperature is 40℃~100℃, and the annealing time is 1 min~10 min.

2. The epitaxial growth template according to claim 1, characterized in that, The solvent is selected from at least one of N,N-dimethylformamide and dimethyl sulfoxide.

3. A tin-based perovskite thin film, characterized in that, It is prepared by the following method: Formamidin hydroiodide, ethylamine hydroiodide, and ethylenediamine dihydroiodate are dissolved in a solvent to obtain a cationic solution; The cationic solution is uniformly coated onto the epitaxial growth template according to any one of claims 1-2, and then annealed to obtain a tin-based perovskite film.

4. The tin-based perovskite thin film according to claim 3, characterized in that, The molar ratio of formamidin hydroiodate, ethylamine hydroiodate, and ethylenediamine dihydroiodate is 1:(0.1~0.4):(0.01~0.05). The solvent is selected from formic acid or isopropanol.

5. The tin-based perovskite thin film according to claim 3, characterized in that, The coating is spin coating, the spin coating speed is 5000 rpm to 7000 rpm, and the spin coating time is 20 s to 40 s; The annealing temperature is 40℃~100℃, and the annealing time is 5 min~20 min.

6. A tin-based perovskite solar cell, characterized in that, It includes a transparent conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, a hole blocking layer, and a cathode electrode, which are stacked sequentially from bottom to top; The perovskite light-absorbing layer is the tin-based perovskite thin film according to any one of claims 3-5.

7. The tin-based perovskite solar cell according to claim 6, characterized in that, The transparent conductive substrate is selected from ITO conductive glass or FTO conductive glass. The hole transport layer is made of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid); The electron transport layer is made of at least one of fullerenes and fullerene derivatives, wherein the fullerene derivatives include indanedion-C. 60 Biadduct, [6,6]-phenyl-C 61 - Isomethyl butyrate; The material used in the hole blocking layer includes one of copper bath and polyethyleneimine; The cathode electrode includes a silver electrode.

8. The tin-based perovskite solar cell according to claim 6, characterized in that, The hole transport layer has a thickness of 30 nm to 40 nm; the perovskite light-absorbing layer has a thickness of 200 nm to 400 nm; the electron transport layer has a thickness of 30 nm to 40 nm; the hole blocking layer has a thickness of 8 nm to 10 nm; and the cathode electrode has a thickness of 100 nm to 110 nm.

Images