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 PbI2 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.