Isothiourea hydrochloride modified perovskite solar cell and preparation method thereof

Abstract

The invention relates to an isothiourea hydrochloride modified perovskite solar cell and a preparation method, the isothiourea hydrochloride modified perovskite solar cell comprises a conductive substrate, an electron transport layer, a perovskite layer, a hole transport layer and an electrode layer which are sequentially arranged from bottom to top, and a buried interface modification layer is arranged between the electron transport layer and the perovskite layer. The buried bottom interface modification layer is modified by isothiourea hydrochloride, and by using a plurality of effective functional groups in the isothiourea hydrochloride, the surface oxygen vacancy of the electron transport layer can be passivated, the energy level matching between the electron transport layer and the perovskite layer is optimized, the energy level barrier is reduced, and the electron transfer and extraction are more efficient; secondly, deposition and growth of a perovskite thin film are facilitated, the grain size of perovskite is increased, the grain size distribution is more uniform, and the problem of poor interface contact between the electron transport layer and the perovskite layer is effectively improved; finally, the high-quality perovskite thin film can effectively passivate perovskite defects, and the photoelectric conversion efficiency and the stability of the perovskite cell are improved at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy materials, and in particular to an isothiourea hydrochloride-modified perovskite solar cell and a preparation method thereof. Background Art

[0002] In today's new energy field, solar cell technology has become a research hotspot in the field of new energy because it can directly convert solar energy into electrical energy and effectively meet the needs of sustainable development of environmental energy. Among them, perovskite solar cells have excellent optoelectronic properties such as high light absorption coefficient, low exciton binding energy, and high carrier mobility. In particular, the photoelectric conversion efficiency has achieved a breakthrough from 3.8% to 26.41%, almost close to the highest value of single-crystal silicon efficiency of 26.81%. In perovskite solar cells, the electron transport layer (ETL) has two major functions: electron extraction and transmission and hole blocking. It plays a pivotal role in the overall photovoltaic performance of the device. However, the large number of oxygen vacancies and surface dangling bonds on the surface and other grain boundaries and surface defects will seriously affect the charge transfer, especially causing the open circuit voltage of perovskite solar cells to decrease and fill factor loss, and also leading to insufficient stability of perovskite solar cells, causing serious loss of their optoelectronic performance until it disappears. In addition, defects at the bottom interface of the perovskite layer (PVK) will also lead to unnecessary non-radiative recombination losses, further damaging the performance of solar cells. Therefore, a simple and effective surface regulation method is urgently needed to minimize the defects at the buried interface of perovskite solar cells (i.e., between the perovskite layer (PVK) and the underlying electron transport layer (ETL)) to improve charge transfer and stability, thereby significantly improving the photoelectric conversion efficiency and stability of perovskite solar cells. Summary of the invention

[0003] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a perovskite solar cell modified with isothiourea hydrochloride and a preparation method thereof, so as to reduce the defects at the buried interface of the perovskite solar cell (i.e., between the perovskite layer and the underlying electron transport layer), thereby improving the photoelectric conversion efficiency and stability of the perovskite solar cell.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A perovskite solar cell modified with isothiourea hydrochloride comprises a conductive substrate, an electron transport layer, a perovskite layer, a hole transport layer and an electrode layer which are arranged in sequence from bottom to top, a buried interface modification layer is provided between the electron transport layer and the perovskite layer, and the buried interface modification layer is modified with isothiourea hydrochloride.

[0006] Furthermore, the isothiourea hydrochloride comprises several functional group sites, wherein the functional group sites at least comprise CS, C=N bond, NC=O, HNC and Cl - .

[0007] Furthermore, the buried interface modification layer has a thickness of 10-50 nm.

[0008] Furthermore, the isothiourea hydrochloride is any one of carboxyethyl isothiourea hydrochloride and [2-(dimethylamino)ethyl]isothiourea dihydrochloride.

[0009] In order to achieve the above object, the present invention also adopts the following technical solutions:

[0010] A method for preparing an isothiourea hydrochloride-modified perovskite solar cell comprises the following steps:

[0011] Step S1, preparing an electron transport layer on a conductive substrate;

[0012] Step S2, preparing a buried interface modification layer containing isothiourea hydrochloride on the electron transport layer;

[0013] Step S3, preparing a perovskite layer on the buried interface modification layer;

[0014] Step S4, preparing a hole transport layer on the perovskite layer;

[0015] Step S5, preparing an electrode layer on the hole transport layer.

[0016] Furthermore, step S2 specifically includes:

[0017] The modification solution containing isothiourea hydrochloride is dripped onto the upper surface of the electron transport layer, and spin coating and annealing are performed to form a buried interface modification layer containing isothiourea hydrochloride.

[0018] Further, the volume of the dropwise addition is 20-100 μL;

[0019] The spin coating condition is to spin coat at a rotation speed of 3000-5000 rpm for 30 seconds;

[0020] The annealing condition is annealing at 60-150° C. for 3-10 min.

[0021] Furthermore, the preparation steps of the modification solution are:

[0022] The isothiourea-containing hydrochloride modifying agent and ultrapure water are mixed evenly to obtain the modified solution.

[0023] Furthermore, the concentration of the modification solution is 0.1-5 mg / ml.

[0024] Furthermore, the mixing method is ice bath ultrasound.

[0025] In summary, compared with the prior art, the present invention has at least the following beneficial effects:

[0026] The invention relates to an isothiourea hydrochloride-modified perovskite solar cell and a preparation method thereof. The perovskite solar cell comprises a conductive substrate, an electron transport layer, a perovskite layer, a hole transport layer and an electrode layer which are sequentially arranged from bottom to top. A buried interface modification layer is arranged between the electron transport layer and the perovskite layer. The buried interface modification layer is modified by isothiourea hydrochloride and utilizes multiple effective functional groups in the isothiourea hydrochloride. On the one hand, the surface oxygen vacancies of the electron transport layer can be passivated, the surface dangling bonds can be reduced, and the energy level matching between the electron transport layer and the perovskite layer can be optimized, the energy level barrier can be reduced, and the transfer and extraction of electrons can be more efficient. On the other hand, the buried interface modification layer can improve the hydrophilicity of the interface of the electron transport layer, which is beneficial to the deposition and growth of the perovskite film, thereby regulating the perovskite crystallization process, increasing the perovskite grain size and making the grain size distribution more uniform, and effectively improving the poor interface contact problem between the electron transport layer and the perovskite layer. At the same time, the high-quality perovskite film can effectively passivate the perovskite defects and improve the photoelectric conversion efficiency and stability of the perovskite cell. The isothiourea hydrochloride-modified perovskite solar cell of the present invention is easy to prepare, the interface defects of the modified perovskite solar cell are reduced, and the photoelectric conversion efficiency, open circuit voltage, short circuit current and fill factor are significantly improved, which is conducive to promoting the commercial application of perovskite cells and has broad application prospects and market space. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 This is a schematic structural diagram of a perovskite solar cell modified with isothiourea hydrochloride provided by the present invention.

[0029] Figure 2 This is a scanning electron microscope image of Example 1 provided by the present invention.

[0030] Figure 3 This is a scanning electron microscope image of Example 2 provided by the present invention.

[0031] Figure 4 This is a scanning electron microscope image of Comparative Example 1 provided by the present invention.

[0032] Figure 5 This is a forward and reverse sweep current density-voltage curve diagram of Example 1 provided by the present invention.

[0033] Figure 6 This is a forward and reverse sweep current density-voltage curve diagram of Example 2 provided by the present invention.

[0034] Figure 7 This is a forward and reverse sweep current density-voltage curve diagram of Comparative Example 1 provided by the present invention.

[0035] Figure 8 This is a comparison chart of the normalized efficiency-time curves of Example 1, Example 2 and Comparative Example 1 provided by the present invention.

[0036] Description of reference numerals:

[0037] 1. Conductive substrate; 2. Electron transport layer; 3. Buried interface modification layer; 4. Perovskite layer; 5. Hole transport layer; 6. Electrode layer. DETAILED DESCRIPTION

[0038] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0040] As attached Figure 1 As shown, the present invention provides an isothiourea hydrochloride-modified perovskite solar cell, comprising a conductive substrate 1, an electron transport layer 2, a perovskite layer 4, a hole transport layer 5 and an electrode layer 6 arranged in sequence from bottom to top, a buried interface modification layer 3 is provided between the electron transport layer 2 and the perovskite layer 4, and the buried interface modification layer 3 is modified by isothiourea hydrochloride.

[0041] Specifically, the present invention utilizes multiple effective functional groups in isothiourea hydrochloride, which can, on the one hand, passivate oxygen vacancies on the surface of the electron transport layer 2 and reduce surface dangling bonds, while optimizing the energy level matching between the electron transport layer 2 and the perovskite layer 4, suppressing non-radiative recombination at the interface, reducing the energy level barrier, and making the transfer and extraction of electrons more efficient; on the other hand, the buried interface modification layer 3 can improve the hydrophilicity of the interface of the electron transport layer 2, which is beneficial to the deposition and growth of the perovskite film, thereby regulating the perovskite crystallization process, increasing the perovskite grain size and making the grain size distribution more uniform, and effectively improving the poor interface contact problem between the electron transport layer 2 and the perovskite layer 4; at the same time, high-quality perovskite films can effectively passivate perovskite defects and improve the photoelectric conversion efficiency and stability of perovskite cells.

[0042] In some embodiments of the present invention, the material of the conductive substrate 1 is any one of FTO and ITO, preferably FTO.

[0043] In certain embodiments of the present invention, the material of the electron transport layer 2 is any one of TiO2, SnO2, ZnO, ZnO and ZnS, preferably SnO2.

[0044] In certain embodiments of the present invention, the material of the hole transport layer 5 is any one of PTAA, P3HT, Spiro-OMeTAD, CuI, and CuSCN, preferably Spiro-OMeTAD.

[0045] In some embodiments of the present invention, the material of the electrode layer 6 is any one of Au, Ag, Al and Cu, preferably Ag.

[0046] In certain embodiments of the present invention, the isothiourea hydrochloride comprises several functional groups, including at least CS, C=N bond, NC=O, HNC and Cl. - .

[0047] Specifically, the C-S bond in the isothiourea hydrochloride can match the energy levels between the electron transport layer 2 and the perovskite layer 4, suppress the non-radiative recombination at the interface, reduce the energy level barrier, and play a role in efficient electron transfer; there are a large number of atoms lacking coordination around the perovskite layer 4. Due to the configuration of the C=N double bond in the isothiourea hydrochloride, it can effectively combine with a large number of surrounding under-coordinated atoms on the perovskite layer 4; the NC=O bond and the HNC bond, combined to fill the oxygen vacancies on the electron transport layer 2, effectively passivate the surface of the electron transport layer 2; finally, Cl - It can fill the halogen vacancy defects of the perovskite layer 4 and improve the surface morphology of the perovskite layer 4. The longitudinal arrangement of the entire isothiourea molecule plays a bridging role.

[0048] In certain embodiments of the present invention, the thickness of the buried interface modification layer 3 is 10-50nm. When the thickness of the buried interface modification layer 3 is too thin, i.e., less than 10nm, it will not be able to play its modification function, and when the thickness of the buried interface modification layer 3 is too thick, i.e., greater than 50nm, it will cause the transfer of electrons between the electron transport layer 2 and the perovskite layer 4 to be blocked. Preferably, the thickness of the buried interface modification layer 3 is 10-20nm.

[0049] In certain embodiments of the present invention, the isothiourea hydrochloride is any one of carboxyethylisothiourea hydrochloride and [2-(dimethylamino)ethyl]isothiourea dihydrochloride.

[0050] In addition to the above-mentioned isothiourea hydrochloride-modified perovskite solar cell, the present invention also provides a preparation method for the above-mentioned isothiourea hydrochloride-modified perovskite solar cell. The preparation method of the isothiourea hydrochloride-modified perovskite solar cell and the above-mentioned perovskite solar cell can correspond to each other.

[0051] A method for preparing an isothiourea hydrochloride-modified perovskite solar cell comprises the following steps:

[0052] Step S1, preparing an electron transport layer on a conductive substrate;

[0053] Specifically, after the conductive substrate is cleaned and dried, the electron transport layer is spin-coated at a rotation speed of 3000-5000 rpm until it covers the entire surface of the conductive substrate, and then heated at 150°C for 30 minutes to form an electron transport layer on the conductive substrate. In order to prevent non-wetting during the subsequent spin coating process, the assembled conductive substrate containing the electron transport layer is treated with ozone or plasma for 10-30 minutes to remove various impurity groups adsorbed on the surface of the conductive substrate, including solution molecules, free radicals and other debris.

[0054] Furthermore, the electron transport layer is any one of TiO2, SnO2, ZnO, ZnO and ZnS, and most preferably SnO2. When the electron transport layer is SnO2, the preferred preparation process of SnO2 includes: diluting an appropriate amount of commercial colloid SnO2 (15% W) according to a volume ratio of SnO2 commercial colloid to ultrapure water of 4:1, placing it on a magnetic stirrer and stirring it evenly for 1 hour, and filtering the stirred diluted solution with a 0.22-0.45 μm filter head for standby use.

[0055] Step S2, preparing a buried interface modification layer containing isothiourea hydrochloride on the electron transport layer;

[0056] In certain embodiments of the present invention, the treated conductive substrate containing the electron transport layer is transferred to a spin coating station, and a modification solution containing isothiourea hydrochloride is dripped onto the upper surface of the electron transport layer, and spin coating and annealing are performed to form a buried interface modification layer containing isothiourea hydrochloride.

[0057] In certain embodiments of the present invention, the volume of the drop is 20-100 μL; the spin coating condition is 3000-5000 rpm for 30 seconds; and the annealing condition is annealing at 60-150° C. for 3-10 minutes.

[0058] In certain embodiments of the present invention, the preparation step of the modification solution containing isothiourea hydrochloride is as follows: uniformly mixing the modification agent containing isothiourea hydrochloride with ultrapure water to obtain the modification solution.

[0059] In certain embodiments of the present invention, the concentration of the modification solution is 0.1-5 mg / ml.

[0060] In certain embodiments of the present invention, the isothiourea hydrochloride-containing modifier is preferably an isothiourea hydrochloride selected from carboxyethylisothiourea hydrochloride and [2-(dimethylamino)ethyl]isothiourea dihydrochloride.

[0061] In certain embodiments of the present invention, the mixing method is ice bath sonication.

[0062] Step S3, preparing a perovskite layer on the buried interface modification layer.

[0063] Specifically, the substrate after the buried interface modification is placed on a spin coater in a glove box, 20-100 μL of 1.0-1.6 M PbI2 solution is dripped on the upper surface of the buried interface modification layer, and the solution is spin-coated at a rotation speed of 500-3000 rpm for 5-30 seconds until the entire surface is covered, and annealed at an annealing temperature of 50-90°C for 2-20 minutes. After the annealing is completed, 20-100 μL of a mixed ammonium salt solution is dripped on the surface, and the solution is spin-coated at a rotation speed of 500-3000 rpm for 5-30 seconds, and annealed at an annealing temperature of 120-170°C in an environment of 30-40% RH air humidity for 5-30 minutes to form a perovskite layer.

[0064] The preparation of the PbI2 solution includes the following specific steps: mixing PbI2 and CsI in a set ratio to obtain a first mixture, adding the first mixture to a mixed solution composed of DMF and DMSO in a volume ratio of 4:1-1:4, placing it on a 70°C magnetic stirrer and heating and stirring for 2-6 hours until the solution is completely dissolved and transparent, to obtain a PbI2 solution, wherein Pb in the PbI2 solution + The concentration is 1.0-1.6 mg / ml, and the ratio is set to Cs + Pb+ 0.2-1% of mass.

[0065] Furthermore, the preparation of the mixed ammonium salt solution includes the following specific steps: adding a mixture consisting of FAI, MAI, MACl and MABr to a solvent, placing it on a magnetic stirrer and dissolving it for 1-6 hours until the solution is clear; the solvent is any one of methanol, ethanol, propanol, isopropanol, chlorobenzene, ethyl acetate and ether, or a combination of several of them in any ratio.

[0066] Step S4: preparing a hole transport layer on the perovskite layer.

[0067] Specifically, a pre-configured solution containing hole transport layer materials is spin-coated onto the upper surface of the perovskite layer at a rotation speed of 3000 rpm for 30 seconds to form a hole transport layer.

[0068] In certain embodiments of the present invention, the solution containing the hole transport layer material is any one of a PTAA solution, a P3HT solution, a Spiro-OMeTAD solution, a CuI solution and a CuSCN solution.

[0069] Step S5, preparing an electrode layer on the hole transport layer to obtain an isothiourea hydrochloride-modified perovskite solar cell.

[0070] In order to further illustrate the technical solution of the present invention, the preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0071] The reagents and materials used in the following examples are all commercially available.

[0072] Example 1

[0073] Step S1, clean the conductive substrate FTO with deionized water, ethanol, acetone, and isopropanol in sequence by ultrasonic cleaning for 15 minutes each and then dry;

[0074] 1 ml of commercial colloid SnO2 (15% W) was diluted according to the volume ratio of colloid to ultrapure water of 4:1, placed on a magnetic stirrer and stirred for 1 hour, and then the dilution was filtered using a 0.45 μm water filter;

[0075] The filtered SnO2 solution was spin-coated at 4000 rpm for 30 seconds, and then placed on a hot plate at 150°C for 30 minutes to form an electron transport layer on the conductive substrate. The conductive substrate containing the SnO2 electron transport layer was treated with ozone for 25 minutes for standby use.

[0076] Step S2, 1 mg of carboxyethyl isothiourea hydrochloride was dissolved in 2 ml of ultrapure water, and ultrasonicated in an ice bath for 30 min to prepare a carboxyethyl isothiourea hydrochloride modification solution with a concentration of 0.5 mg / ml;

[0077] The treated conductive substrate containing the SnO2 electron transport layer was transferred to a spin coating table, and 50 μL of a modification solution containing carboxyethyl isothiourea hydrochloride was dropped onto the upper surface of the SnO2 electron transport layer. The solution was spin coated at 4500 rpm for 30 seconds, and then annealed on a hot plate at 120°C for 5 minutes to form a buried interface modification layer containing carboxyethyl isothiourea hydrochloride.

[0078] Step S3, 1.4M PbI2 and CsI are mixed according to Cs + Pb + 0.5% by mass of PbI2 and 0.5% by weight of PbI2 were mixed to obtain a first mixture, the first mixture was added to a mixed solution consisting of DMF and DMSO in a volume ratio of 4:1, and the mixture was heated and stirred on a 70° C. magnetic stirrer for 3 h until the PbI2 solution was completely dissolved and transparent, thereby obtaining a PbI2 solution;

[0079] A mixture consisting of 60 mg FAI, 3 mg MAI, 9 mg MACl and 2 mg MABr was added to 1 ml isopropanol and dissolved on a magnetic stirrer for 6 h until the solution became clear to obtain a mixed ammonium salt solution;

[0080] The substrate after the buried interface modification is placed on a spin coater in a glove box, 30 μL of PbI2 solution is dripped on the upper surface of the buried interface modification layer, and the solution is spin-coated at a rotation speed of 2000 rpm for 25 seconds until the entire surface is covered, and annealed at an annealing temperature of 70°C for 5 minutes. After the annealing is completed, 100 μL of a mixed ammonium salt solution is dripped on the surface, and the solution is spin-coated at a rotation speed of 1700 rpm for 30 seconds, and annealed at an annealing temperature of 150°C for 15 minutes in an environment of 30-40% RH air humidity to form a perovskite layer;

[0081] Step S4, spin coating the pre-configured Spiro-OMeTAD solution onto the upper surface of the perovskite layer at a rotation speed of 3000 rpm for 30 seconds to form a hole transport layer;

[0082] Step S5, preparing a Ag electrode layer on the hole transport layer.

[0083] Carboxyethyl isothiourea hydrochloride modified perovskite solar cells were obtained.

[0084] Example 2

[0085] Step S1, clean the conductive substrate FTO with deionized water, ethanol, acetone, and isopropanol in sequence by ultrasonic cleaning for 15 minutes each and then dry;

[0086] 1 ml of commercial colloid SnO2 (15% W) was diluted according to the volume ratio of colloid to ultrapure water of 4:1, placed on a magnetic stirrer and stirred for 1 hour, and then the dilution was filtered using a 0.45 μm water filter;

[0087] The filtered SnO2 solution was spin-coated at 4000 rpm for 30 seconds, and then placed on a hot plate at 150°C for 30 minutes to form an electron transport layer on the conductive substrate. The conductive substrate containing the SnO2 electron transport layer was treated with ozone for 20 minutes for standby use.

[0088] Step S2, 1 mg of [2-(dimethylamino)ethyl]isothiourea dihydrochloride was dissolved in 1 ml of ultrapure water, and ultrasonicated on ice for 30 min to prepare a [2-(dimethylamino)ethyl]isothiourea dihydrochloride modification solution with a concentration of 1 mg / ml;

[0089] The treated conductive substrate containing the SnO2 electron transport layer was transferred to a spin coating table, and 75 μL of a modification solution containing [2-(dimethylamino)ethyl]isothiourea dihydrochloride was dropped onto the upper surface of the SnO2 electron transport layer. The solution was spin coated at 5000 rpm for 30 seconds, and then annealed on a hot plate at 150°C for 3 minutes to form a buried interface modification layer containing [2-(dimethylamino)ethyl]isothiourea dihydrochloride.

[0090] Step S3, 1.6M PbI2 and CsI are mixed according to Cs + Pb + 1% by mass of PbI2 and 1% by weight of PbI2 were mixed to obtain a first mixture, the first mixture was added to a mixed solution consisting of DMF and DMSO in a volume ratio of 4:1, and the mixture was heated and stirred on a magnetic stirrer at 70°C for 6 hours until the PbI2 solution was completely dissolved and transparent.

[0091] A mixture consisting of 50 mg FAI, 3 mg MAI and 5 mg MACl was added to 1 ml ethanol and dissolved on a magnetic stirrer for 6 h until the solution became clear to obtain a mixed ammonium salt solution;

[0092] The substrate after the buried interface modification is placed on a spin coater in a glove box, 50 μL of PbI2 solution is dripped on the upper surface of the buried interface modification layer, and the solution is spin-coated at a rotation speed of 3000 rpm for 5 seconds until the entire surface is covered, and annealed at an annealing temperature of 80°C for 2 minutes. After the annealing is completed, 100 μL of a mixed ammonium salt solution is dripped on the surface, and the solution is spin-coated at a rotation speed of 2000 rpm for 5 seconds, and annealed at an annealing temperature of 170°C for 5 minutes in an environment of 30-40% RH air humidity to form a perovskite layer;

[0093] Step S4, spin coating the pre-configured Spiro-OMeTAD solution onto the upper surface of the perovskite layer at a rotation speed of 3000 rpm for 30 seconds to form a hole transport layer;

[0094] Step S5: preparing a Ag electrode layer on the hole transport layer.

[0095] [2-(Dimethylamino)ethyl]isothiourea dihydrochloride salt-modified perovskite solar cells were obtained.

[0096] Comparative Example 1

[0097] The difference between this comparative example and Example 1 is that only steps S1, S3, S4 and S5 are performed, that is, only a perovskite solar cell without a buried bottom interface modification layer is obtained, and the parameters in the operations of steps S1, S3, S4 and S5 are the same.

[0098] The perovskite solar cells prepared in Examples 1-2 and Comparative Example 1 are marked as Example 1, Example 2 and Comparative Example 1, respectively. Then, Examples 1-2 and Comparative Example 1 are tested, and the specific test results are analyzed as follows:

[0099] (1) Microstructure analysis: as shown in the attached Figure 2-4 As shown, the grain size of the perovskite modified with isothiourea hydrochloride in Example 1 and Example 2 is significantly larger than the grain size of the perovskite modified with isothiourea hydrochloride in Comparative Example 1 without isothiourea hydrochloride modification. This is because the buried interface modification layer can improve the hydrophilicity of the electron transport layer interface, which is beneficial to the deposition and growth of the perovskite film, thereby regulating the perovskite crystallization process, increasing the perovskite grain size and making the grain size distribution more uniform, effectively improving the poor interface contact problem between the electron transport layer and the perovskite layer; and it can be seen that the defects of the perovskite grains modified with isothiourea hydrochloride in Example 1 and Example 2 are significantly reduced, indicating that the perovskite defects are effectively passivated.

[0100] (2) Photoelectric test: The test scan rate is 0.01V / s, and the scan directions are forward and reverse.

[0101] As attached Figure 5-7 As shown, the JV performance curves of various embodiments and comparative examples are obtained, wherein the short-circuit current density of the battery obtained in comparative example 1 is 22.92 mA / cm 2 , the open circuit voltage is 1.03V, the fill factor is 0.73%, and the photoelectric conversion efficiency is 17.2%; while the short circuit current density of the perovskite solar cell modified with carboxyethyl isothiourea hydrochloride is 23.07mA / cm 2, the open circuit voltage is 1.06V, the fill factor is 0.76%, and the photoelectric conversion efficiency is 18.51%; the short circuit current density of the perovskite solar cell modified with [2-(dimethylamino)ethyl]isothiourea dihydrochloride is 23.03mA / cm 2 , the open circuit voltage is 1.07V, the fill factor is 0.77%, and the photoelectric conversion efficiency is 19.04%. The results show that compared with comparative example 1, the photovoltaic performance indicators of the perovskite solar cell modified with isothiourea hydrochloride are significantly improved, indicating that the interface defects of the perovskite solar cell modified with isothiourea hydrochloride are effectively passivated, which improves the transfer and extraction efficiency of electrons.

[0102] Table 1 J-V curve parameters

[0103]

[0104]

[0105] (3) Stability test: Unpackaged devices were tested in the dark at 50% relative humidity.

[0106] As attached Figure 8 As shown, the normalized efficiency-time variation curves of the embodiments and comparative examples were obtained, wherein embodiment 1 can still maintain a normalized efficiency of 91% after 500 hours, embodiment 2 can still maintain a normalized efficiency of 89% after 500 hours, and the normalized efficiency of comparative example 1 is reduced to 70% after 500 hours, which indicates that the buried interface modification layer modified with isothiourea hydrochloride can greatly improve the stability of perovskite solar cells.

[0107] In summary, it can be seen from the comparative examples and the results of each embodiment that the present invention provides a buried interface modification layer between the electron transport layer and the perovskite layer, and the buried interface modification layer is modified by isothiourea hydrochloride, and multiple effective functional groups in isothiourea hydrochloride are used to effectively passivate the interface, and the photoelectric conversion efficiency and stability of the perovskite layer are effectively improved, and the buried interface modification layer can improve the hydrophilicity of the electron transport layer interface, which is conducive to the deposition and growth of the perovskite film, thereby regulating the perovskite crystallization process, increasing the perovskite grain size and making the grain size distribution more uniform, and effectively improving the poor interface contact problem between the electron transport layer and the perovskite layer. Compared with the prior art, the present invention has significant progress.

[0108] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. An isothiourea hydrochloride-modified perovskite solar cell, comprising a conductive substrate, an electron transport layer, a perovskite layer, a hole transport layer and an electrode layer arranged in sequence from bottom to top, characterized in that: A buried interface modification layer is provided between the electron transport layer and the perovskite layer, and the buried interface modification layer is modified by isothiourea hydrochloride.

2. The isothiourea hydrochloride-modified perovskite solar cell according to claim 1, characterized in that: The isothiourea hydrochloride comprises several functional groups, which at least include CS, C=N bond, NC=O, HNC and Cl - .

3. The isothiourea hydrochloride-modified perovskite solar cell according to claim 1, characterized in that: The thickness of the buried interface modification layer is 10-50nm.

4. The isothiourea hydrochloride-modified perovskite solar cell according to claim 1, characterized in that: The isothiourea hydrochloride is any one of carboxyethyl isothiourea hydrochloride and [2-(dimethylamino)ethyl]isothiourea dihydrochloride.

5. A method for preparing an isothiourea hydrochloride-modified perovskite solar cell, characterized in that: The following steps are involved: Step S1, preparing an electron transport layer on a conductive substrate; Step S2, preparing a buried interface modification layer containing isothiourea hydrochloride on the electron transport layer; Step S3, preparing a perovskite layer on the buried interface modification layer; Step S4, preparing a hole transport layer on the perovskite layer; Step S5, preparing an electrode layer on the hole transport layer.

6. The preparation method according to claim 5, characterized in that: Step S2 specifically includes: The modification solution containing isothiourea hydrochloride is dripped onto the upper surface of the electron transport layer, and spin coating and annealing are performed to form a buried interface modification layer containing isothiourea hydrochloride.

7. The method for preparing an isothiourea hydrochloride-modified perovskite solar cell according to claim 6, characterized in that: The volume of the dropwise addition is 20-100 μL; The spin coating condition is to spin coat at a rotation speed of 3000-5000 rpm for 30 seconds; The annealing condition is annealing at 60-150° C. for 3-10 min.

8. The method for preparing an isothiourea hydrochloride-modified perovskite solar cell according to claim 6, characterized in that: The preparation steps of the modification solution are: The isothiourea-containing hydrochloride modifying agent and ultrapure water are mixed evenly to obtain the modified solution.

9. The method for preparing an isothiourea hydrochloride-modified perovskite solar cell according to claim 8, characterized in that: The concentration of the modification solution is 0.1-5 mg / ml.

10. The method for preparing the isothiourea hydrochloride-modified perovskite solar cell according to claim 8, characterized in that: The mixing method is ice bath ultrasound.

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