Improved Solar Cell Performance of 1.68 eV Perovskite Absorber Through Scaffold and Solvent Engineering for Scalable Two-Step Hybrid Deposition

Abstract

Two‐step perovskite deposition has attracted significant interest due to its compatibility with textured substrates. However, implementing a scalable hybrid process combining inorganic‐layer coevaporation with blade coating remains challenging, as solvent incompatibility during the second‐step conversion often limits perovskite crystallization, film uniformity, and device performance. Here, we demonstrate a solvent coordination engineering strategy for 1.68 eV wide‐bandgap perovskite absorbers fabricated via a vacuum/solution hybrid two‐step process while retaining highly volatile alcohol‐based solvents. By optimizing the inorganic layer to minimize residual PbI 2 and introducing a Lewis base coordinating additive ( N ‐methyl‐2‐pyrrolidone, NMP) into an IPA‐based second‐step solvent, controlled perovskite formation is achieved without resorting to high‐boiling‐point or low‐volatility solvents. The enhanced coordination between NMP and precursor salts moderates crystallization kinetics, improving the absorber morphology, crystallinity, uniformity, and optoelectronic properties. Consequently, an average improvement in open‐circuit voltage ( V oc ) from 1.08 to 1.09 V and the fill factor from 75% to 80.5% without surface passivation is exhibited. With interface improvement, a champion efficiency of 20.7%, a fill factor of 82.3%, and a V oc of 1.16 V are achieved. This solvent strategy enables the production of high‐quality wide‐bandgap perovskites suitable for tandem solar cell integration and has the potential for scale‐up.