Lewis base additive diazine induced efficient and stable perovskite solar cells made in ambient air via a post-adding strategy

Lewis base molecules as common additives provide a promising strategy for regulating the nucleation and growth of high-performance perovskite solar cells (PSCs). However, the more complex nucleation pathways encountered by all-air-processed PSCs present more formidable challenges. Herein, we propose a post-adding strategy that incorporated the weakly alkaline molecule additive diazine into the perovskite precursor only introducing diazine prior to the spin-coating step to delay Lewis adduct generation and slow down the crystallization rate of perovskite in ambient air. Specifically, the diazine contained electron-rich N atoms not only can suppress the charged defects of perovskite films, but also improve the energy level alignment between the light absorption layer and the transport layers. By optimizing the concentration of diazine, the resulting PSCs fabricated in air without control atmosphere achieve a champion PCE of over 21 % and a high V OC of 1.2 V. Furthermore, the unencapsulated devices maintain over 80 % of their initial PCE after 1920h in the full ambient air condition (25 ± 5 % RH). This post-adding strategy of diazine provides a new view for finding suitable Lewis base additives and optimizing the fabrication conditions to realize efficient and stable all-air-processed PSCs.