Application of Bidirectional Passivation Agents at the Tin Oxide/Perovskite Interface to Enhance the Performance of Perovskite Solar Cells

In recent years, there have been reports of continuous breakthroughs in the efficiency of perovskite solar cells, and perovskite solar cells based on n–i–p device structures have achieved certified efficiencies of around 27%. The key factor behind these latest breakthroughs is the use of tin oxide as an electron transport layer, which enhances device performance by effectively controlling the extraction, transport, and recombination of charges. However, the performance of perovskite devices is affected by issues such as energy level mismatch and numerous interface defects at the tin oxide electron transport layer/perovskite interface. To address these issues, researchers have optimized the electron transport layer/perovskite interface using different materials. Among them, the material with bidirectional passivation effect, namely bidirectional passivator, has attracted the attention of researchers. This article mainly analyzes the application and prospect of bidirectional passivators at the SnO 2 /perovskite interface in the n–i–p structure. It can not only passivate the defects of the lower tin oxide layer and reduce the agglomeration of SnO 2 crystals, but also improve the growth of the upper perovskite and passivate the defects of the perovskite layer, thereby optimizing the interface contact of SnO 2 /perovskite and significantly improving the photoelectric performance of the device. The bidirectional passivators are classified into three categories, inorganic salts, acid radical salts, and amino organic compounds, and the mechanism of their bidirectional passivation effect on the SnO 2 /perovskite interface is elaborated in detail in this paper. Finally, the further development and challenges of bidirectional passivators are discussed.