Gas‐Quenching Assisted Crystallization of Wide‐Bandgap Perovskite for Triple‐Junction Perovskite Solar Cells

The theoretical power conversion efficiency limit of multi-junction solar cells exhibits a progressive enhancement with increasing number of junctions. However, the performance of all-perovskite triple-junction solar cells is currently limited by the quality of the ≈2 eV wide bandgap perovskite layer, primarily due to its rapid and uncontrolled crystallization process. In this study, a gas quenching method into the fabrication of wide-bandgap perovskite films is introduced, effectively modulating the crystallization kinetics by elevating the nucleation energy barrier, thereby achieving smooth films with uniform vertical halogen distribution. The derived wide bandgap perovskite solar cells exhibit a high open-circuit voltage of 1.42 V with excellent reproducibility. Based on the optimized WBG perovskite, all-perovskite triple-junction solar cells that achieve a remarkable efficiency of 25.3% with an open-circuit voltage of 3.23 V under AM 1.5G illumination are fabricated. This work provides an effective strategy to overcome the crystallization challenge in WBG perovskites, paving the way for the development of efficient and stable multi-junction perovskite solar cells.