Dual-Site Synergistic Passivation for CsPbBr3 Perovskite Solar Cells with Record 1.707 V Voc and 11.23% Efficiency

Abstract

Achieving high-quality perovskite films with minimal defect states is critical for the development of efficient and stable perovskite solar cells (PSCs). In this work, we introduce diphenylphosphine (DPP) additives into the PbBr2 precursor solution to passivate defects and enhance device performance. By systematically varying the carbon chain length of DPP molecules, we reveal that phosphorus atoms coordinate with undercoordinated Pb2+ ions in the perovskite lattice, effectively reducing defect densities and improving film quality. The experimental results demonstrate that 1,3-bis (diphenylphosphino) propane (DPPP) with optimal carbon chain length achieves significantly improved defect passivation efficiency through enhanced lattice parameter matching with perovskite structures, whereas excessively long chains hinder performance due to steric effects. The best doping amount of DPPP with the ideal carbon chain length yields a power conversion efficiency (PCE) of 11.23% and a record open-circuit voltage (Voc) of 1.707 V. Furthermore, unencapsulated CsPbBr3 PSCs with DPPP exhibit exceptional thermal and humidity stability, maintaining more than 90 % of the initial performance after 1800 h under 80 °C or 80% relative humidity.