Homogenizing Morphology and Composition of Methylammonium-Free Wide-Bandgap Perovskite for Efficient and Stable Tandem Solar Cells

A facile and eco-friendly dimethyl sulfoxide-mediated solution aging (DMSA) treatment is presented to control the crystallization dynamics of methylammonium (MA)-free wide-bandgap (WBG) perovskite films, enhancing film quality, and morphology for high-performance tandem solar cells. The comprehensive structural, morphological, and characterization analyses reveal that the DMSA treatment significantly enhances composition and morphology homogeneity while suppressing halide segregation. Consequently, opaque, and semi-transparent MA-free WBG perovskite solar cells (PSCs) exhibit remarkable power conversion efficiencies (PCEs) of 18.28% and 17.61%, respectively. Notably, the unencapsulated DMSA-treated devices maintain 95% of the initial PCE after 900 h of continuous operation at 55 °C ± 5 °C. Furthermore, stacking semi-transparent DMSA-treated PSCs as top cells in a 4T tandem configuration, along with silicon heterojunction (SHJ), lead–tin (Pb–Sn) alloyed PSCs, and organic photovoltaics (OPV) as bottom cells, yields impressive PCEs of 28.09%, 26.09%, and 25.28%, respectively, for the fabricated tandem cells. This innovative approach opens new avenues for enhancing the photo-stability and photovoltaic performance of perovskite-based tandem solar cells.