Regulating crystal growth and enhancing efficiency in CsPbBr3 perovskite solar cells through the incorporation of Pb(SCN)2 additive in ambient multistep deposition process

Abstract

All−inorganic CsPbBr<inf>3</inf> perovskite has served as a light−absorbing layer in solar cells due to its excellent humidity and temperature tolerance. However, the photovoltaic performance of CsPbBr<inf>3</inf>−based solar cells remains low because of poor film morphology, crystallinity, and high defect density. Additive engineering efficiently controls the crystallization dynamics, suggesting a high−quality perovskite film. This research introduces Pb(SCN)<inf>2</inf> as an additive to the CsPbBr<inf>3</inf> perovskite by incorporating Pb(SCN)<inf>2</inf> into the PbBr<inf>2</inf> precursor solution in a multistep spin−coating method conducted in ambient air. The PbBr<inf>2</inf> films modified with Pb(SCN)<inf>2</inf> exhibited large grain size and low wettability, hindering the crystallization process of CsPbBr<inf>3</inf> perovskite films because of the interaction between SCN⁻ and Pb²⁺ ions. The modified CsPbBr<inf>3</inf> perovskite film demonstrated full coverage, enhanced crystallinity, reduced defect density, a smoother surface, and larger grain size. The optimal performance of the modified CsPbBr<inf>3</inf> solar cells achieved the highest power conversion efficiency (PCE) of 5.85 %. Moreover, the modified CsPbBr<inf>3</inf> device without encapsulation exhibited remarkable long−term stability under ambient conditions, lasting over 2000 h, outperforming the pristine version. This study emphasizes that the Pb(SCN)<inf>2</inf> additive is valuable for preparing high−quality and stable inorganic CsPbBr<inf>3</inf> perovskite films in ambient air, which could benefit photovoltaics and other optoelectronic applications.