Achieving 17.46% Efficiency CsPbI2Br Perovskite Solar Cells via Multifunction Lead Chloride‐Modified ZnO Electron Transporting Layer

Abstract CsPbI 2 Br perovskite solar cells (PSCs) have garnered significant attention owing to their remarkable thermal stability and desirable bandgap. However, CsPbI 2 Br‐based devices still face critical challenges, particularly at the interfaces between the active layer and adjacent components. In this study, a multifunctional ZnO composition has developed as the electron transporting layer (ETL) for CsPbI 2 Br PSCs, enabling simultaneous efficient charge extraction and passivation of buried interface defects in CsPbI 2 Br. The nanocomposite, composed of PbCl 2 ‐modified ZnO (PbCl 2 ‐ZnO), facilitates the regulation of bandgap and conduction band to align the energy level of ETL and CsPbI 2 Br. Additionally, the residual PbCl 2 at the buried interface of the perovskite incorporates into the perovskite lattice, reducing I defect and thus improving film quality. The improved energy level alignment at the ETL/CsPbI 2 Br interface and the suppressed I defect‐induced carrier nonradiative recombination result in a remarkable reduction in energy loss from 0.73 to 0.52 eV. Finally, the PbCl 2 ‐ZnO hybrid nanocomposite ETL significantly enhances the efficiency of CsPbI 2 Br PSCs, increasing it from 14.15% to 17.46%, representing one of the highest reported power conversion efficiency (PCE) values for CsPbI 2 Br PSCs. These findings demonstrate the potential of PbCl 2 ‐ZnO hybrid nanocomposite as an effective ETL for CsPbI 2 Br PSCs.