A Novel Organic Phosphonate Additive Induced Stable and Efficient Perovskite Solar Cells with Efficiency over 24% Enabled by Synergetic Crystallization Promotion and Defect Passivation

Defect passivation is crucial to enhancing the performance of perovskite solar cells (PSCs). In this study, we successfully synthesized a novel organic compound named DPPO, which consists of a double phosphonate group. Subsequently, we incorporated DPPO into a perovskite solution. The presence of a P═O group interacting with undercoordinated Pb²⁺ yielded a perovskite film of superior crystallinity, greater crystal orientation, and smoother surface. Additionally, the addition of DPPO can passivate defect states and enhance upper layer energy level alignment, which will improve carrier extraction and prevent nonradiative recombination. Consequently, an impressive champion efficiency of 24.24% was achieved with a minimized hysteresis. Furthermore, the DPPO-modified PSCs exhibit enhanced durability when exposed to ambient conditions, maintaining 95% of the initial efficiency for 1920 h at an average relative humidity (RH) of 30%.