| Metal halide perovskite materials have attracted a lot of attention from researchers in the field of photovoltaics due to their excellent semiconductor properties and solution-preparable characteristics.Over the past decade,the certified power conversion efficiency of perovskite solar cells（PSCs）has reached to 25.7%.The electron transport layer（ETL）is an important component of perovskite solar cells,playing the role of extracting electrons and blocking holes.However,the presence of defects on the ETL surface affects the efficiency and stability of PSCs.This thesis focuses on the study of tin oxide ETL and its interface with perovskite to enhance the efficiency and stability of PSCs by modifying the Sn O2/perovskite interface,developing and using new mixed-valence tin oxide ETLs,and modifying mixed-valence tin oxide ETLs,mainly by:（1）Modification of the interface between Sn O2 and perovskite using the silane coupling agent NQ-62 to obtain PSCs with higher efficiency and better stability.The siloxyl group at one end of NQ-62 is cross-linked by hydrolysis reaction and combines with the hydroxyl group on the surface of Sn O2 to produce a self-assembled layer.A reasonable treatment time of 4 min ensures that the hydroxyl group on the surface of Sn O2is completely reacted and that the self-assembled layer.The multiple amino groups at the other end of NQ-62 enhance the infiltration of Sn O2 into the perovskite and improve the crystallization of perovskite,and passivate the defects in the perovskite,suppressing the non-radiative complex at the interface.The environmental stability of the device is also significantly improved.（2）The controllable preparation of mixed-valence van der Waals tin-based oxides Sn2O3 and Sn3O4 is achieved and its potential as a novel ETL is confirmed.By analyzing their theoretical crystal structures and using Sn Cl2 and Sn Cl4 as the tin sources,different target products are obtained by controlling the ratios of Sn2+and Sn4+using hydrothermal reactions.Stable Sn2O3 and Sn3O4 colloidal dispersions are successfully prepared by controlling the precursor preparation temperature to inhibit the oxidation of Sn2+and improving the dispersion of the products through ion control.Tests show that the synthesized Sn2O3 and Sn3O4 were thermally stable at ambient temperatures below 300°C and 250°C,are n-type semiconductors with lower defect density of states and suitable electron mobility,and are suitable as ETLs for PSCs.（3）Efficient and UV-stable PSCs are prepared using mixed valence tin-based oxides Sn2O3 and Sn3O4 as ETLs.Uniform and dense films are obtained by multiple spin-coating of the dispersions,and the corresponding films do not affect the light transmission of the substrates.Both Sn2O3 and Sn3O4 have a lower density of defect states than Sn O2 and a more suitable energy level alignment with perovskite,showing a better electron extraction capability than Sn O2.The efficiency of PSCs using Sn2O3 and Sn3O4 as ETLs is 22.19%and 21.67%,respectively,which is higher than that of Sn O2 devices with an efficiency of21.03%.In addition,Sn2O3 and Sn3O4 are stable under UV light and form favorable interfacial contacts with perovskite,which suppress the device performance degradation caused by UV irradiation.（4）In order to enhance its electron concentration,Sn3O4 is doped with Yttrium to obtain Sn3O4-based PSCs with higher efficiency.YCl3·6H2O is introduced during the synthesis process,and Y3+partially replaced the Sn2+ions in Sn3O4 to produce an n-type doping effect.The doped Sn3O4 electron concentration is effectively enhanced with higher conductivity and the Fermi energy levels is upward-shifted,which optimize the energy level alignment with perovskite and enhance the built-in electric field and electron extraction ability of Y-Sn3O4 devices,increasing the device efficiency to 23.05%. |
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