A green solvent engineering process for synthesizing perovskite films in high humidity atmospheres for efficient solar cells

Fabrication of highly efficient perovskite solar cells (PSCs) under open air conditions is highly desired for their commercialization. However, it is still a huge challenge to prepare highly efficient PSCs in open air conditions because the perovskite films are highly sensitive to moisture. Additionally, the solvents used for the preparation of perovskite films are usually toxic and should not be handled under open air conditions. These obstacles hinder the efforts to prepare high performance PSCs under open air conditions, especially in high humidity atmospheres. Therefore, the power conversion efficiency (PCE) of PSCs prepared in the open air still lag far behind those prepared in inert atmospheres. The method reported in our previous work that only uses green solvents reduces the concerns surrounding solvent toxicity during the processing of perovskite films in open air conditions. Herein, we propose a new strategy that only uses green solvents, which combines substrate preheating with high-temperature short-time annealing, to prepare high quality perovskite films in a high humidity atmosphere (relative humidity of (70-80%)). Based on this new strategy, a typical PSC that utilizes a perovskite film processed in air under a high humidity atmosphere shows a PCE of 19.86%, which is very close to the PCE of a PSC prepared in an N2-filled glove box. This feasible strategy minimizes the gap between the PCEs of PSCs prepared using green solvents in inert atmospheres and those prepared in a humid atmosphere. These advantages will make this strategy appealing for applications in the future commercialization of PSCs in terms of equipment cost control, efficiency loss minimization and its environmentally friendly nature. High quality perovskite films processed using only green solvents in a high humidity atmosphere.