ANatural Antioxidant Organic Material Modifying theBuried Interface To Regulate the Photovoltaic Performance and Stabilityof Pure Tin-Based Perovskite Solar Cells

Despite showing great potential in lead-free green energy, tin-based perovskite materials still face challenges such as inherent material instability and energy level misalignment with the hole transport layer (HTL), which limits the advancement of tin-based perovskite solar cells (Sn-PSCs). In this work, a natural antioxidant organic small molecule, thiolactic acid (TA), is used to modify the interface between PEDOT:PSS and the tin-based perovskite film. The TA molecule can cross-link to form a network polymer and regulate the microstructure and photoelectrical characteristics of PEDOT:PSS. Meanwhile, TA contains CO and CS groups, which can interact with Sn²⁺ to inhibit its oxidation. Moreover, the introduction of TA interfacial modification effectively improves the morphology of the perovskite film, suppresses interfacial charge recombination, and promotes carrier transport. Thus, TA-modified Sn-PSCs achieve a champion power conversion efficiency of 9.03%, surpassing 6.92% of the control PSCs. Even after being stored for 1000 h in a nitrogen atmosphere, the unencapsulated devices with TA modification still maintain 95.4% of their original PCE, compared to only 66.5% of the control devices. This study demonstrates the significance of the PEDOT:PSS/tin-perovskite interfacial modification on the efficiency and stability of Sn-PSCs.