A method to improve the efficiency and stability of tin-lead alloy perovskite cells

Abstract

The present invention belongs to a method for improving the photoelectric conversion efficiency and stability of tin-lead alloy perovskite solar cells, and specifically relates to a method for effectively regulating the energy disorder of the film by hydrogen bonding and coordination with the tin-lead alloy perovskite to inhibit the photoelectric conversion efficiency and stability of the tin-lead alloy perovskite solar cells. 2+ The method of reducing the defect density of the film and optimizing the extraction and transport of carriers is to add additives to SnF 2 The present invention effectively inhibits the Sn-lead alloy perovskite film from being doped with an additive by introducing an organic small molecule containing a sulfoxide group into the perovskite film. 2+ It can reduce the oxidation of the film and reduce the defect density of the film, optimize the carrier extraction and transmission, and improve the photoelectric conversion efficiency and stability of the battery device; the material cost is low and it is easy to implement in the process.

Description

Technical Field

[0001] The present invention belongs to a method for improving the photoelectric conversion efficiency and stability of tin-lead alloy perovskite solar cells, and specifically relates to using organic small molecules with reducing and electron-rich sulfoxide groups to effectively regulate film energy disorder through hydrogen bonding and coordination with tin-lead alloy perovskite, thereby inhibiting Sn 2+ The present invention relates to a method for reducing the oxidation of the film and the defect density of the film, thereby optimizing the extraction and transport of carriers. Background Art

[0002] Energy disorder of halide perovskites caused by phase instability or structural instability can lead to higher Urbach energies (E u ) and significantly reduce the open circuit voltage (V OC ). According to the Schockley-Queisser limit theory, for single-junction Sn-Pb alloy perovskite solar cells with optimal band gap, the electronic disorder is related to Sn 2+ Oxidized to Sn 4+ Although various strategies have been used to enhance perovskite crystallization and suppress Sn 2+ To Sn 4+ However, the corresponding device performance and long-term stability are still worse than those of pure lead-based perovskite solar cells. Therefore, it remains a major challenge to achieve efficient and excellently stable Sn-Pb alloy perovskite solar cells. Here, we introduce the organic small molecule 1-bromo-4-(methylsulfinyl)benzene (BBMS) together with SnF2 into the perovskite precursor solution, and regulate the energy disorder and suppress the Sn in the perovskite film through the hydrogen bonds and coordination bonds between BBMS and perovskite. 2+ The BBMS-treated battery device showed high photoelectric conversion efficiency and excellent stability. Summary of the invention

[0003] The purpose of the invention is to provide a method for improving the photoelectric conversion efficiency and stability of a tin-lead alloy perovskite solar cell device.

[0004] To achieve the above purpose, the present invention adopts the following technical solution:

[0005] The additive is added together with SnF2 into a tin-lead alloy perovskite precursor solution, and a tin-lead alloy perovskite film doped with the additive is obtained through spin coating and annealing operations.

[0006] Among them, the additive used is a sulfoxide derivative, the scientific name of which is 1-bromo-4-(methylsulfinyl)benzene, abbreviated as BBMS.

[0007] Preferred:

[0008] Mix the required components in proportion, use DMSO / DMF as solvent, stir thoroughly until completely dissolved, and obtain FA 0.7 MA 0.25 Cs 0.05 Sn 0.5 Pb 0.5 I3 precursor solution. The tin-lead alloy perovskite film was prepared by the anti-solvent method, the anti-solvent was chlorobenzene, the precursor solution used in the control group contained SnF2 but no additives, and the experimental group contained SnF2 and additives of different concentrations. The obtained wet perovskite film was then heat treated.

[0009] The mass concentration of the additive in the precursor solution is 0 to 1.0 mg / mL.

[0010] The heat treatment temperatures of the film are 100°C and 65°C.

[0011] More preferably:

[0012] SnF2 and additives were added to the precursor solution, and the film was prepared by spin coating and heated to 100°C and then to 65°C, and then the battery device was assembled. When the additive concentration was 0.5mg / ml, the battery device obtained the best photovoltaic performance parameters, and there was a downward trend when changing other concentrations.

[0013] The additive is a sulfoxide derivative, and its scientific name is 1-bromo-4-(methylsulfinyl)benzene, referred to as BBMS.

[0014] Its structural formula is:.

[0015] The perovskite structure of the tin-lead alloy perovskite film is ABX3, A is a cation containing formamidine NH2-CH=NH2 (FA) ions, methylamine CH3NH3 (MA) ions and cesium (Cs) ions; B is Sn ions and Pb ions; and X is I ions.

[0016] The tin-lead alloy perovskite film obtained by the above method improves energy disorder and inhibits Sn 2+ The oxidation of the film is reduced, the defect density of the film is reduced, the extraction and transmission of charges is optimized, and the charge recombination at the interface is reduced, which greatly improves the photovoltaic performance and working life of the device, which is particularly important for the commercial application of tin-lead alloy perovskite battery devices.

[0017] The advantages of the present invention are:

[0018] The present invention introduces BBMS small molecules into the perovskite film, which can effectively regulate energy disorder and inhibit Sn 2+The oxidation of the film is reduced, the defect density of the film is reduced, the extraction and transmission of charges are optimized, and the charge recombination at the interface is reduced, which greatly improves the photovoltaic performance and stability of the device. The material cost is low and it is easy to implement in the process.

[0019] The present invention introduces BBMS small molecules into the initial film, which can be prepared by conventional spin coating method. The sulfoxide groups contained in the material have strong interaction with Sn and Pb ions of perovskite.

[0020] The perovskite film containing BBMS small molecules prepared by the method of the present invention has fewer defects and reduced charge recombination losses. The tin-lead alloy perovskite film prepared based on the present invention exhibits better perovskite film quality and longer carrier lifetime, and the stability of the corresponding device is also significantly improved.

[0021] The process of the invention is easy to operate, has good repeatability and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 XRD patterns of the perovskite film prepared before and after BBMS was introduced into the precursor solution provided in the embodiment of the present invention.

[0023] Figure 2 SEM photos of the perovskite film prepared before and after the introduction of BBMS into the precursor solution provided in the embodiment of the present invention; the left picture is before the addition of BBMS, and the right picture is after the addition of 0.5 mg / ml BBMS.

[0024] Figure 3 The NMR spectra of formamidine iodide (FAI), an important component of the precursor provided in the embodiment of the present invention, before and after the introduction of BBMS.

[0025] Figure 4 XPS spectra of the perovskite film prepared before and after the introduction of BBMS into the precursor solution provided in the embodiment of the present invention.

[0026] Figure 5 The IV curves of the perovskite battery prepared before and after the introduction of BBMS into the precursor solution provided in the embodiment of the present invention.

[0027] Figure 6 The stability curves of the unpackaged perovskite cells prepared before and after the introduction of BBMS into the precursor solution provided in the embodiment of the present invention.

[0028] Figure 7 SCLC curves of the perovskite film prepared before and after the introduction of BBMS into the precursor solution provided in the embodiment of the present invention.

[0029] Figure 8 V of the perovskite battery prepared before and after the introduction of BBMS into the precursor solution provided in the embodiment of the present inventionoc -Light intensity dependency curve.

[0030] Fig. 9 The TPV curves of the perovskite cell prepared before and after the introduction of BBMS into the precursor solution provided in the embodiment of the present invention.

[0031] Fig.10 EIS curves of perovskite cells prepared before and after BBMS was introduced into the precursor solution provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] 1. Device Preparation

[0033] First, ITO was used as the glass substrate and washed with alkaline cleaning solution, deionized water, anhydrous isopropanol, and anhydrous ethanol in sequence, and dried in an oven. The glass substrate was treated with O2-plasma for 5 minutes before use. The PEDOT:PSS solution was spin-coated on the clean glass substrate at 4000rpm for 30s, and then placed on a hot stage and heated at 140℃ for 20min to obtain a dense PEDOT:PSS hole transport layer, which was then transferred to a nitrogen box.

[0034] Secondly, accurately weigh 216.68 mg FAI, 71.54 mg MAI, 335.27 mg SnI2, 414.91 mg PbI2, and 23.38 mg CsI, and dissolve them in 1 mL of mixed solvent, DMSO:DMF=1:1 v / v. In addition, the precursor solution also contains 7.05 mg SnF2, and the composition is FA 0.7 MA 0.25 Cs 0.05 Sn 0.5 Pb 0.5 I3 (trace SnF2) precursor solution. Take 30μL of the precursor solution and spin coat it on the substrate containing the hole transport layer at 1000rpm for 10s and then at 4000rpm for 50s. In the second step, spray 400μL of chlorobenzene at 20s. The precursor solution of the control group does not contain BBMS, while the experimental group contains BBMS and the optimal concentration is 0.5mg / ml. The resulting wet film was annealed on a 100℃ hot stage for 10min and then transferred to a 65℃ hot stage for annealing for 20min. Compared with the experimental group, the control group perovskite film significantly improved the crystallinity of the perovskite, resulting in an increase in the XRD peak intensity. The peak position did not move and no new peaks appeared, indicating that the doping process did not induce the formation of new phases (see Figure 1 ). At the same time, SEM images show that the addition of BBMS leads to a smoother film, with significantly larger grains and fewer grain boundaries (see Figure 2). NMR and XPS spectra reflect the hydrogen bonding and coordination between the additive BBSM and the perovskite (see Figure 3 and 4 ). In addition, the SCLC curve also shows that the defect density of the perovskite film with the addition of BBMS is greatly reduced, which is inseparable from the improvement of the morphology and crystal particle size of the perovskite film.

[0035] Finally, according to the prior art, an electron transport layer C is deposited on the surface of the two different perovskite films obtained above. 60 , hole blocking layer Bathocuproine (BCP) and silver electrode. The solar cell device was assembled and then the IV performance was measured. The measurement conditions were forward and reverse scanning between -0.1V and 0.9V. The photoelectric conversion efficiency of the device containing BBMS was significantly improved, and the most important thing was to improve the open circuit voltage (V OC ), indicating that the non-radiative recombination losses in the device are reduced.

[0036] The solar cell obtained in this example was placed in a nitrogen environment at room temperature or 60°C, and the nitrogen stability and thermal stability were tested respectively. Figure 6 It can be seen that the stability of the battery device doped with BBMS has been significantly improved. OC ) and light intensity (Light intensity) dependence curve can reflect the degree of defect-assisted recombination in the perovskite film by calculating the ideal factor n. The n value of the perovskite film passivated by BBMS decreases from 1.80 to 1.51, indicating that the defect-assisted recombination in the film is suppressed after the introduction of BBMS. At the same time, it can be understood that the introduction of BBMS in the perovskite film reduces the defect density (see Figure 8 ), which is consistent with the result of SCLC curve. It can be seen from the TPV curve (see Fig. 9 ), the perovskite film with BBMS has a longer decay time, which means that the introduction of BBMS can effectively prolong the carrier lifetime and inhibit non-radiative recombination. EIS curves are often used to further understand the effects of additives on charge transport and recombination (see Fig.10 ), and the resistance values ​​were obtained by fitting the circuit diagram in the inset. The battery device containing BBMS showed a lower series resistance (R s ) and higher composite resistance (R rec ), indicating that the introduction of BBMS in battery devices effectively promotes charge transfer and inhibits charge recombination.

Claims

1. A method for improving the photoelectric conversion efficiency and stability of tin-lead alloy perovskite solar cell devices using multifunctional organic small molecules, characterized in that: In the process of preparing the tin-lead alloy perovskite film, an additive is added to a precursor solution to obtain a tin-lead perovskite film doped with the additive; The additive is 1-bromo-4-(methylsulfinyl)benzene.

2. The method for improving the photoelectric conversion efficiency and stability of tin-lead alloy perovskite solar cell devices by using multifunctional organic small molecules according to claim 1, characterized in that: By introducing an additive 1-bromo-4-(methylsulfinyl)benzene into the perovskite film, the energy disorder of the film is adjusted and the Sn 2+ oxidation and reduce the defect density of the film, optimizing the extraction and transport of carriers.

3. The method for improving the photoelectric conversion efficiency and stability of tin-lead alloy perovskite solar cell devices by using multifunctional organic small molecules according to claim 1 or 2, characterized in that: The mass concentration of the additive in the precursor solution is 0.5 mg / ml.

4. The method for improving the photoelectric conversion efficiency and stability of tin-lead alloy perovskite solar cell devices by using multifunctional organic small molecules according to claim 1 or 2, characterized in that: Additives of a certain mass concentration are added to a tin-lead alloy perovskite precursor solution, and a tin-lead alloy perovskite film doped with the additive can be obtained through spin coating and annealing operations; wherein the solvent of the precursor solution is a mixture of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

5. The method for improving the photoelectric conversion efficiency and stability of tin-lead alloy perovskite solar cell devices by using multifunctional organic small molecules according to claim 2, characterized in that: The heat treatment temperatures of the film are 100°C and 65°C.

6. The method for improving the photoelectric conversion efficiency and stability of tin-lead alloy perovskite solar cell devices by using multifunctional organic small molecules according to claim 1 or 2, characterized in that: The perovskite structural formula of the tin-lead alloy perovskite film is ABX3, A is a cation containing one or two or more of methylamine CH3NH3 (MA) ions, formamidine NH2-CH=NH2 (FA) ions and cesium (Cs) ions; B is Pb metal ions and Sn metal ions; X is one or two or more of I, Br, and Cl ions.

7. A tin-lead alloy perovskite film prepared by the method of claim 1, characterized in that: The additive-doped tin-lead alloy perovskite film is prepared according to the method of claim 1.

8. An application of the film according to claim 7, characterized in that: The application of the additive-doped tin-lead alloy perovskite film in solar cells, light-emitting devices or detection devices improves the photoelectric conversion efficiency and stability of the perovskite solar device.

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