High‐Speed Deposition of Large‐Area Narrow‐Bandgap Perovskite Films for All‐Perovskite Tandem Solar Mini‐Modules

Abstract Developing all‐perovskite tandem solar cells is an effective approach to extend the limit of power conversion efficiency. However, fast preparation of large‐area and high‐quality narrow‐bandgap Sn‐based perovskite films still remains a major challenge in fabricating all‐perovskite tandem modules. Here high‐crystalline and compact narrow‐bandgap perovskite films with an area over 100 cm 2 are well prepared by combining compositional, solvent and additive engineering. The use of 2‐methoxyethanol as a solvent enables the fast deposition of narrow‐bandgap perovskite films. Adding proper amounts of dimethyl sulfoxide and surfactant L‐α‐phosphatidylcholine into the narrow‐bandgap perovskite precursor effectively enhances the crystallinity and coverage of the resulting perovskite films, respectively. Based on these studies, narrow‐bandgap perovskite and all‐perovskite tandem mini‐modules with an aperture area of 10.4 cm 2 are constructed and exhibit high efficiencies of 13.2% and 16.4%, respectively. This study provides an option for fast deposition of high‐quality narrow‐bandgap perovskite films, which is beneficial for the scalable production of all‐perovskite tandem solar modules.