Lead Oxalate-Induced Nucleation Retardation for High-Performance Indoor and Outdoor Perovskite Photovoltaics.

Perovskite solar cells have attracted worldwide attention as one of the key research areas in the field of thin-film photovoltaics. Although they exhibit easy solution processability, it is important to effectively control the crystallization of the light-absorbing layer, which affects the performance and stability of devices. Here, we present lead oxalate (PbC2O4) as a nonhalide lead constituent of the perovskite precursor solution, which contributes to anion replacement during thin film annealing. This strategy limits the perovskite nucleation rate and retards crystallization. As a result, we achieved excellent perovskite films with larger grains and fewer defects. The open-circuit voltage of the optimal device under 1 sun illumination rose to 1.12 V with a power conversion efficiency (PCE) of 20.20%. In addition, the indoor PCE at 1000 lux can reach 34.86%. This nonhalide lead compound dopant provides a guide for the crystallization of perovskite materials and paves a way for the fabrication of nonhalide perovskite solar cells.