Synergistic Surface Reconstruction and Defect Passivation via Guanidine Sulfonate for High-Efficiency Perovskite Photovoltaics

Perovskite films have long suffered from various defects located at grain boundaries and surfaces (GBS), especially residual lead iodide (PbI₂), which can seriously impair the photoelectric conversion efficiency (PCE) and long-term stability of the corresponding photovoltaic devices. Herein, guanidine sulfamate (GSM), with desired −NH₂, S═O, and Gua⁺ functional groups, is introduced to the perovskite surface by a post-treatment process to achieve high-quality films with fewer defects. It was found that −NH₂ and S═O in GSM contribute to the passivation of various defects in perovskites and suppress non-radiative recombination, thus improving the interfacial carrier transport efficiency. Meanwhile, the guanidine (Gua⁺) cations promote grain fusion during post-treatment to achieve large-sized grains and effectively reduce residual PbI₂ content. Moreover, the optimized perovskite films also exhibited better energy level alignment and surface hydrophobicity. Consequently, the champion PCE of the optimized perovskite solar cells (PSCs) was increased from 21.69 to 23.85% at the appropriate GMS post-treatment concentration, along with a significant improvement in storage stability and light stability.