Comprehensive Passivation on Different Charged Ions and Defects for High Efficiency and Stable Perovskite Solar Cells

Trap-mediated nonradiative charge recombination poses a significant obstacle to achieving high-efficiency and stability in metal-halide perovskite solar cells (PSCs). Utilizing the interactions between functional groups of molecules and perovskite defects as surface defect passivation strategies is a common approach in addressing this challenge. Nevertheless, the challenge lies in developing a comprehensive molecule capable of effectively depressing and passivating different charged defects. This study explores a multifunctional organic salt neostigmine methyl sulfate (NMS), to finely regulate the crystallization of perovskite film, thereby minimizing defects and passivating surface defects. The C═O and S═O of NMS coordinate with Pb²⁺, while the oxygen atoms of S═O interact with FA⁺ through hydrogen bonds (O∙∙∙H─N). The interactions involving S─O⁻ with Pb²⁺ ions and ─N(CH₃)₃⁺ with the negative halide ions are predominantly electrostatic interactions. Therefore, through NMS treatment, the crystallization process of perovskite film is delayed, energy levels are optimized, and the surface defects are effectively passivated. This leads to a notable decrease in defect density and an improved alignment of perovskite energy levels, enhancing carrier transfer and extraction within the device. Consequently, a stabilized power conversion efficiency (PCE) of 24.95% is achieved. Even after 50 d, the device maintains its environmental stability retaining 89.39%.