Efficient and Stable Tin‐Lead Mixed Perovskite Solar Cells Using Post‐Treatment Additive with Synergistic Effects

Abstract Inhibiting the oxidation of Sn 2+ during the crystallization process of Sn−Pb mixed perovskite film is found to be as important as the oxidation resistance of precursor solution to achieve high efficiency, but less investigated. Considering the excellent reduction feature of hydroquinone and the hydrophobicity of tert‐butyl group, an antioxidant 2,5‐di‐tert‐butylhydroquinone (DBHQ) was introduced into Sn−Pb mixed perovskite films using an anti‐solvent approach to solve this problem. Interestingly, we find that DBHQ can act as function alterable additive during its utilization. On the one hand, DBHQ can restrict the oxidation of Sn 2+ during the crystallization process, facilitating the fabrication of high‐quality perovskite film; on the other hand, the generated oxidation product 2,5‐di‐tert‐butyl‐1,4‐benzoquinone (DBBQ) can functionalize as defect passivator to inhibit the charge recombination. As a result, this synergetic effect renders the Sn−Pb mixed PSC a power conversion efficiency (PCE) up to 23.0 %, which is significantly higher than the reference device (19.6 %). Furthermore, the unencapsulated DBQH‐modified PSCs exhibited excellent long‐term stability and thermal stability, with the devices maintaining 84.2 % and 78.9 % of the initial PCEs after aging at 25 °C and 60 °C for 800 h and 120 h under N 2 atmosphere, respectively. Therefore, the functional alterable strategy provides a novel cornerstone for high‐performance Sn−Pb mixed PSCs.