Choline Chloride-Modified SnO₂ Achieving High Output Voltage in MAPbI₃ Perovskite Solar Cells

Choline chloride as a photosynthesis promoter is important for increasing plant yield, and we have found that it has a similar effect in perovskite solar cells (PSCs). Here, we propose the innovation of using molecular self-assembly methods to produce a choline chloride monolayer on the surface of the SnO2; this monolayer works as a passivation layer that reduces the surface oxygen vacancies and improves the performance of CH3NH3PbI3 (MAPbI3) PSCs. The MAPbI3 PSC based on SnO2 modified by choline chloride (Chol-SnO2) electron transport layer (ETL) achieves an optimal power conversion efficiency (PCE) of 18.90% under one solar illumination. The PCE is increased by 10–25% compared to the device without modification, and hysteresis is significantly reduced by eliminating the charge accumulation between the interface of the perovskite and ETL. More importantly, the MAPbI3 PSC based on Chol-SnO2 ETL exhibits a higher open-circuit voltage (VOC) of 1.145 V compared to the control device (1.071 V). This work provides a very simple and effective way to improve PSC performance, which has long-term significance for the sustainable development of energy.