Enhanced Efficiency and Intrinsic Stability of Wide-Bandgap Perovskite Solar Cells Through Dimethylamine-Based Cation Engineering.

High efficiency and stable wide-bandgap (WBG) perovskite solar cells (PSCs) are crucial for the development of perovskite-based tandem solar cells. However, the efficiency and stability of WBG PSCs are compromised by significant phase segregation and surface defects. In this study, we introduce a cation engineering strategy for WBG perovskite, employing a two-step sequential method that incorporates dimethylamine hydroiodide (DMAI) into the lead halide complex during the initial step. The addition of DMAI modifies the crystal structure and grain growth of the perovskite film, leading to improved crystal quality, reduced photo-induced halide segregation, decreased defect density, and enhanced charge carrier mobility. Consequently, we achieved a champion power conversion efficiency (PCE) of 21.9 % for 1.68 eV WBG PSCs. Furthermore, the stability of PSCs based on DMA-doped perovskite was significantly improved. After 1500 hours of exposure to ambient air, the unencapsulated device retained an impressive 80.6 % of its initial efficiency. This result highlights the substantial potential for stable and efficient WBG PSCs.