A buried interface material and a flexible perovskite solar cell prepared by the same

Abstract

The application discloses a buried bottom interface material and a flexible perovskite solar cell prepared by the buried bottom interface material. The structural formula of the buried bottom interface material is as follows: or wherein X is Cl or Br. The buried bottom interface modification material can be prepared into an interface modification layer by spin coating or printing. The bromine atom on the benzene ring can form a strong hydrogen bond with the FA cation vacancy of the perovskite layer, and then can uniformly passivate the defects of the lower interface of the perovskite photovoltaic film, improve the crystal quality, make the contact between the perovskite layer and the hole transport layer more compact, and there is no gap, so that the efficiency and stability of the flexible device are improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of new photovoltaic materials, and particularly relates to a buried bottom interface material and a flexible perovskite solar cell prepared therefrom. BACKGROUND

[0002] With the rapid development of electronic industry technology, people's demand for portable electronic products, curved display devices and wearable flexible devices is increasing, among which, the flexible perovskite solar cell is attracting more and more attention due to its light weight, good flexibility and low production cost. However, since the commonly used flexible substrate cannot withstand high temperature (> 150℃), all deposition and processing processes of the flexible device must be carried out at a lower temperature to ensure that the substrate will not be negatively affected. In addition, since the flexible substrate is more rough than the conventional rigid glass substrate, when depositing the perovskite thin film, the morphology of the substrate will significantly affect the growth and crystallization process of the perovskite thin film, thereby inevitably causing a large number of defects in the perovskite active layer thin film, resulting in non-radiative recombination of carriers at the interface and in the perovskite active layer, which damages the efficiency and stability of the photovoltaic cell.

[0003] Although there have been reports of using organic or inorganic materials as interface materials to modify the surface of the substrate, thereby preparing perovskite thin films with high density and few defects. However, these materials are basically used for the preparation of two-dimensional perovskite materials on the upper surface of the perovskite, which will change the original structure of the perovskite to some extent, which may have some adverse effects. At the same time, the methods reported in these reports are basically used for rigid substrates of glass substrates, most of which cannot be directly applied to low-temperature deposition processes. Therefore, it is particularly important to design and develop interface materials suitable for flexible substrates.

[0004] Organic arylammonium salt is a material widely used in perovskite solar cells, which can not only effectively solve the lattice mismatch problem between the perovskite photovoltaic thin film and the flexible substrate surface, but also passivate ionic defects at the interface of the cell, reduce interface recombination, improve interface charge transport efficiency, and improve the efficiency and stability of the flexible perovskite solar cell. F and Br are the most commonly used halogen atoms to replace hydrogen atoms on the benzene ring, among which F atoms have the strongest hydrophobicity due to their large electronegativity and small radius. Therefore, fluorine-containing organic arylammonium salt is not suitable for modifying the lower surface of the perovskite, because the too strong hydrophobicity will cause poor wettability, thereby slowing down the nucleation rate of the perovskite, which will make the perovskite grain grow, but the uniformity of the film will be poor, thereby causing a large number of nanometer defects at the buried bottom interface of the perovskite. Therefore, it is crucial to develop an organic arylammonium salt material with appropriate energy level arrangement, good contact and few defects and a low-temperature deposition method for obtaining high-performance and stable flexible perovskite cells. SUMMARY

[0005] The present application aims to overcome the deficiencies of the interface passivation technology of the flexible perovskite solar cell, and provide a buried bottom interface material suitable for flexible devices, solve the technical problems that the existing flexible devices cannot withstand high temperature and are easy to bend when heated, thereby causing the perovskite and the lower interface hole transport layer to have voids due to different expansion coefficients, and the lower interface of the perovskite is prone to have nano defects.

[0006] To achieve the above-mentioned purpose, the present application realizes through the following technical solutions:

[0007] A buried bottom interface material, the structural formula of which is:

[0008]

[0009] In the formula, X is Cl or Br.

[0010] Preferably, the above-mentioned buried bottom interface material is prepared by neutralizing p-bromo-phenethylamine or o-bromo-phenethylamine with a halogenated hydrogen acid-base.

[0011] The present application also provides a flexible perovskite solar cell, which is provided with a buried bottom interface modification layer between the hole transport layer and the perovskite layer of the flexible perovskite solar cell, and the buried bottom interface modification layer is made of the above-mentioned buried bottom interface material.

[0012] Preferably, the preparation method of the above-mentioned flexible perovskite solar cell comprises the following steps:

[0013] providing a flexible substrate;

[0014] preparing a hole transport layer on the flexible substrate;

[0015] preparing a buried bottom interface modification layer on the hole transport layer;

[0016] preparing a perovskite layer on the buried bottom interface modification layer;

[0017] preparing an electron transport layer on the perovskite layer;

[0018] preparing a metal electrode on the electron transport layer.

[0019] Preferably, the flexible substrate is a PEN / ITO conductive flexible substrate, and the material forming the hole transport layer is MeO-2PACz.

[0020] Preferably, the material forming the perovskite layer is FA 0.92 MA 0.08 PbI 2.76 Br 0.24 .

[0021] Preferably, the preparation method of the buried bottom interface modification layer comprises: dissolving the buried bottom interface material in an organic solution to obtain a modification agent solution; spin coating the modification agent solution on the surface of the hole transport layer to form the buried bottom interface modification layer after annealing treatment.

[0022] Preferably, the organic solvent is one of N,N-dimethylformamide and toluene; and the concentration of the modification agent solution is 5-40 mM.

[0023] Preferably, when the modification agent solution is spin coated on the surface of the hole transport layer, the spin coating is performed at a speed of 3000-5000 rpm for 30 s, more preferably at a speed of 5000 rpm for 30 s, and the acceleration is 2000 rpm / s.

[0024] Preferably, the annealing treatment is performed at a temperature of 80-100 DEG C for 5-10 min.

[0025] The present application has the following beneficial effects:

[0026] The present application provides a multi-anchoring site arylammonium salt buried bottom interface modification material, the ammonium ion on the ammonium salt can repair the negative charged defects through the interaction of ionic bond and hydrogen bond, and the nitrogen atom contains lone pair of electrons, which can coordinate with the positive charged Lewis acid defects; the bromine atom on the benzene ring can form a strong hydrogen bond with the FA cation vacancy, so that the perovskite layer and the hole transport layer are more compactly connected without gap.

[0027] The buried bottom interface modification material provided by the present application can be prepared into an interface modification layer through spin coating or printing, thereby uniformly passivating the defects of the lower interface of the perovskite photovoltaic film, improving the crystal quality, and improving the efficiency and stability of the flexible device.

[0028] The synthesis process of the buried bottom interface modification material of the present application is simple, low in cost, and can form an interface modification layer on the hole transport layer by using a low-temperature deposition process, thereby meeting the needs of low-temperature preparation of flexible perovskite devices. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings of the embodiments will be briefly introduced as follows.

[0030] Figure 1 It is the nuclear magnetic hydrogen spectrum of the product 4-Br-PEACl in Example 1;

[0031] Figure 2 It is the surface SEM graph of the perovskite film before and after modification by 4-Br-PEACl in Example 1;

[0032] Figure 3 It is the cross-sectional SEM graph of the perovskite film before and after modification by 4-Br-PEACl in Example 1;

[0033] Figure 4 Current density-voltage curves of the trans-fexible perovskite solar cells before and after modification by 4-Br-PEACl in Example 1.

[0034] Figure 5 Time-resolved photoluminescence spectra of the perovskite thin film before and after modification by 4-Br-PEACl with a concentration of 20 mM in Example 5. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0036] Example 1

[0037] A buried interface material, the structural formula of which is:

[0038]

[0039] The preparation method comprises the following steps: 30 mmol of p-bromo-phenethylamine is added into a round-bottom flask to which 10 mL of ethanol has been added, and the mixture is cooled in an ice bath. 30 mmol of HCl solution (36 wt%) is added dropwise under magnetic stirring. The reaction is carried out at 0°C for 2 hours, and then slowly heated to room temperature. After the reaction is completed, the solvent is evaporated by a rotary evaporator, and the residue is stirred in diethyl ether for 10 min and then filtered, and washed with 5 mL of diethyl ether for 3 times. The washed solid is redissolved in ethanol, and recrystallized after the addition of diethyl ether. The recrystallized solid is filtered and washed with diethyl ether for 3 times. After drying in a nitrogen environment for 24 h, about 24 mmol of solid product p-bromo-phenethylammonium chloride (4-Br-PEACl) is obtained, Figure 1 The nuclear magnetic hydrogen spectrum thereof is shown in Figure 1.

[0040] A flexible perovskite solar cell, the preparation method of which is as follows:

[0041] A PEN / ITO conductive flexible substrate (2 cm x 1.25 cm) is used as the positive electrode of the cell, and the PEN / ITO is ultrasonically cleaned in deionized water and anhydrous ethanol for 5 minutes each. SAM (MeO-2PACz) is used as the hole transport layer material, and is spin-coated on the surface of the flexible substrate by using a spin coater, with the spin-coating conditions being a speed of 3000 rpm and spin-coating for 30 s.

[0042] The above prepared p-bromophenethylammonium chloride (4-Br-PEACl) was dissolved in DMF to prepare an interfacial modification solution of 20 mM, which was continuously shaken in a shaker for more than 2 h; the interfacial modification solution was spin-coated on the PEN / ITO / SAM substrate at a speed of 5000 rpm for 30 s (acceleration of 2000 rpm / s) by using a spin coater, and then annealed at 100 ℃ for 5 min on a heating table to form a buried interfacial modification layer.

[0043] A perovskite layer was spin-coated on the buried interfacial modification layer: FA 0.92 MA 0.08 PbI 2.76 Br 0.24 As the perovskite light-absorbing material, it was spin-coated at a speed of 1000 rpm for 10 s (acceleration of 1000 rpm / s), and then spin-coated at a speed of 5000 rpm for 30 s (acceleration of 2000 rpm / s), and the anti-solvent ethyl acetate (EA) was added at the 10 s of the second step, and finally annealed at 100 ℃ for 1 h to form a perovskite layer.

[0044] An electron transport layer C 60 (23 nm), BCP (8 nm) and a 90 nm electrode silver (Ag) were vacuum evaporated on the perovskite layer in sequence to prepare a trans flexible perovskite solar cell.

[0045] Figure 2 The SEM images of the perovskite surface before and after modification by 4-Br-PEACl in this embodiment can be seen that the grain size of the modified perovskite becomes more uniform. Figure 3 The cross-sectional SEM images of the perovskite before and after modification by 4-Br-PEACl in this embodiment can be clearly seen that after modification, the perovskite layer and the hole transport layer are more compact, and the gap between the two layers is uniformly filled by the buried interfacial modification material provided by the application. Figure 4 The current density-voltage curves of the trans flexible perovskite solar cell before and after modification by 4-Br-PEACl can be seen that the device shows higher output voltage and output current after modification by the buried interfacial material.

[0046] Example 2

[0047] A buried interfacial material was prepared by the same method as in Example 1, except that the hydrogen halide was an HBr solution (48 wt%). After drying in a nitrogen environment for 24 h, about 24 mmol of solid product p-bromophenethylammonium bromide (4-Br-PEABr) was obtained, and its structural formula is shown below. And it was prepared into a flexible perovskite solar cell according to the same method as in Example 1.

[0048]

[0049] Example 3

[0050] A buried interface material was prepared using the same method as in Example 1, except that the bromophenylethylamine derivative was o-bromophenylethylamine. After drying in a nitrogen atmosphere for 24 hours, approximately 24 mmol of the solid product o-bromophenylethylammonium chloride (2-Br-PEACl) was obtained, with the structural formula shown below. Flexible perovskite solar cells were then prepared using the same method as in Example 1.

[0051]

[0052] Example 4

[0053] A buried interface material was prepared using the same method as in Example 1, except that the bromophenylethylamine derivative was o-bromophenylethylamine, and the hydrogen halide was an HBr solution (48 wt%). After drying in a nitrogen atmosphere for 24 hours, approximately 24 mmol of the solid product o-bromophenylethylammonium bromide (2-Br-PEABr) was obtained, with the structural formula shown below. Flexible perovskite solar cells were then prepared using the same method as in Example 1.

[0054]

[0055] Example 5

[0056] The buried interface modification layer and perovskite layer were prepared using the same method as in Example 1, except that the substrate structure used was changed from a PEN / ITO conductive flexible substrate to a pure PEN substrate. To further investigate the modification effect of the organic aryl ammonium salt on the perovskite film, time-resolved photoluminescence spectroscopy of the perovskite film was performed using 485 nm excitation light. The results are as follows: Figure 5 As shown. From Figure 5 As can be seen, the average carrier lifetime of the perovskite modified with 4-Br-PEACl is significantly increased from 582 ns to 901 ns. The longer lifetime indicates that 4-Br-PEACl exhibits superior passivation of defects and the ability to reduce nonradiative recombination of carriers.

[0057] Example 6

[0058] This embodiment investigates the effect of different concentrations of 4-Br-PEACl organic halide solutions on the film thickness. Inverted flexible perovskite solar cells were prepared using different concentrations of 4-Br-PEACl solutions following the same method as in Example 1. The effective area of ​​the cell was 0.16 cm². 2 The simulated solar radiation intensity is 100 mW·cm. -2 This involves testing the photoelectric conversion efficiency under sunlight. Specific test parameters and results are shown in Table 1.

[0059] Table 1 Efficiency of solar cells modified by different concentrations of 4-Br-PEACl

[0060]

[0061] Note: The parameters in the table are forward scans.

[0062] From the data in Table 1, it can be seen that with the increase of the concentration of 4-Br-PEACl solution, the photoelectric conversion efficiency shows a trend of first increasing and then decreasing. When the concentration of the ammonium halide organic solution is 20 mM, the photoelectric conversion efficiency reaches the highest, and when the concentration of 4-Br-PEACl reaches 40 mM, the modified layer is too thick, and the average photoelectric conversion efficiency and the highest photoelectric conversion efficiency are both decreased compared with 20 mM. The unmodified trans flexible perovskite solar cell has the highest photoelectric conversion efficiency of 15.4%, while the battery based on the optimal concentration of 20 mM has the highest photoelectric conversion efficiency of 20.2%.

[0063] Comparative Example 1

[0064] A flexible perovskite solar cell was prepared according to the same method as in Example 1, except that the buried bottom interface material was phenethylammonium iodide (PEAI).

[0065] Comparative Example 2

[0066] A flexible perovskite solar cell was prepared according to the same method as in Example 1, except that the buried bottom interface material was phenethylammonium chloride (PEACl).

[0067] Comparative Example 3

[0068] A flexible perovskite solar cell was prepared according to the same method as in Example 1, except that the buried bottom interface material was phenethylammonium bromide (PEABr).

[0069] Performance test

[0070] The perovskite solar cells prepared in Examples 1-4 and Comparative Examples 1-3 were tested, and the effective area of the battery was 0.16 cm 2 , and the simulated solar light intensity was 100 mW·cm -2 , i.e. the photoelectric conversion efficiency test under the irradiation of one sun light. The test results are shown in Table 2.

[0071] Table 2 Photovoltaic parameters of batteries prepared based on different organic ammonium salts for interface modification layer

[0072] Organic ammonium salt V OC (V) J SC (mA cm -2 )]]> FF (%) PCE (%) PEAI 1.04 21.59 78.34 17.59 PEACl 1.07 21.71 76.46 17.83 PEABr 1.09 21.55 75.05 17.68 2-Br-PEACl 1.08 21.76 76.68 18.14 2-Br-PEABr 1.09 23.34 74.04 18.82 4-Br-PEACl 1.08 22.54 78.10 19.06 4-Br-PEABr 1.10 22.23 75.22 18.42

[0073] Note: The parameters in the table are forward scans.

[0074] As can be seen from Table 2, the interface modification material provided by the present application can significantly improve the battery efficiency. By comparing PEAI, PEACl and PEABr, it can be found that the filling factor of the battery modified by PEAI is the highest, but the voltage is not as high as PEACl and PEABr, and the final efficiency is also slightly lower than the two. However, the photovoltaic parameters of the four batteries modified by the ammonium salt with bromine substitution on the benzene ring provided by the present application are higher than those of the comparative examples, because the bromine atoms on the benzene ring can interact with the FA cations through strong hydrogen bonds, so that the hole transport layer and the perovskite layer are more closely connected.

[0075] In summary, the present application relates to a preparation method of an interface modification material and its application. The preparation steps of the interface modification layer are as follows: adding an ammonium halide salt into an organic solution, mixing uniformly, and preparing an ammonium halide salt organic solution; wherein the ammonium halide salt is prepared by neutralizing p-bromo-phenethylamine or o-bromo-phenethylamine with hydrogen halide acid and base; the ammonium halide salt organic solution is spin-coated on a hole transport layer (HTL), and after low-temperature annealing treatment on a heating table, an interface modification layer is obtained. The ammonium halide salt provided by the present application has low cost, simple synthesis process and easy operation, and can be spin-coated or printed to prepare an interface modification layer, which is suitable for flexible devices and rigid devices, and is conducive to popularization in other photovoltaic device fields.

[0076] It should be noted that each of the above embodiments belongs to the same inventive concept, and the description of each embodiment has its own emphasis. If the description is not exhaustive in individual embodiments, the description in other embodiments can be referred to.

[0077] The above-described embodiments only express the implementation of the present application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A flexible perovskite solar cell, characterized by, The flexible perovskite solar cell is provided with a buried bottom interface modification layer between the hole transport layer and the perovskite layer, and the buried bottom interface modification layer is made of a buried bottom interface material; the structural formula of the buried bottom interface material is: or , In the formula, X is Cl or Br; The buried bottom interface material is prepared by neutralizing p-bromo-phenethylamine or o-bromo-phenethylamine with a halogenated hydrogen acid-base; The preparation method of the flexible perovskite solar cell comprises the following steps: providing a flexible substrate; preparing a hole transport layer on the flexible substrate; preparing a buried bottom interface modification layer on the hole transport layer; the preparation method of the buried bottom interface modification layer comprises the following steps: dissolving a buried bottom interface material in an organic solution to obtain a modification agent solution; spin coating the modification agent solution on the surface of the hole transport layer to form the buried bottom interface modification layer after annealing treatment; preparing a perovskite layer on the buried bottom interface modification layer; preparing an electron transport layer on the perovskite layer; preparing a metal electrode on the electron transport layer. 2.The flexible perovskite solar cell of claim 1, wherein, The flexible substrate is a PEN / ITO conductive flexible substrate, and the material forming the hole transport layer is MeO-2PACz. 3.The flexible perovskite solar cell of claim 1, wherein, The material forming the perovskite layer is FA 0.92 MA 0.08 PbI 2.76 Br 0.24 . 4.The flexible perovskite solar cell of claim 1, wherein, The organic solvent is one of N,N-dimethylformamide and toluene; the concentration of the modification agent solution is 5-40 mM. 5.The flexible perovskite solar cell of claim 1, wherein, When the modification agent solution is spin coated on the surface of the hole transport layer, the spin coating is performed at a speed of 3000-5000 rpm for 30 s, and the acceleration is 2000 rpm / s. 6.The flexible perovskite solar cell of claim 1, wherein, The temperature of the annealing treatment is 80-100 DEG C, and the annealing time is 5-10 min.

Images