Enhanced Photovoltaic Performance and Stability of CsPbI₃ Quantum Dots via Ligand Exchange and Compositional Defect Passivation

Inorganic CsPbI 3 perovskite quantum dots (PQDs) possess excellent optical properties, holding broad application prospects in the field of photovoltaics. However, the issues of a complex surface chemical environment and high compositional defect density for CsPbI 3 PQDs have severely influenced the performance of CsPbI 3 PQD solar cells (PQDSCs). Herein, the sequential treatment strategy based on the ligand exchange of trimethyliodosilane (TMIS) and the compositional defect regulation of formamidinium iodide (FAI) is introduced. Short-chain ligands of TMIS are used to replace the original ligands of CsPbI 3 PQDs and robustly anchor to the PQD surface, which guarantees the high stability and efficient charge carrier transport of CsPbI 3 PQDs. Furthermore, FAI is introduced by the vacancies and dangling bonds as the driving force on the PQD surface to passivate the defects of Cs and I vacancies while reducing the exciton binding energy and band gap of the CsPbI 3 PQDs. Consequently, the power conversion efficiency of PQDSCs is achieved to be 15.07%, which is greatly enhanced compared with that of the control device (12.09%), and only 26% of the initial efficiency is lost after aging under ambient conditions (20–30% RH) for 14 days.