Synergistic Lattice Stabilization and Bandgap Tuning in Wide-Bandgap Perovskite Solar Cells

Wide-bandgap (WBG) perovskites are key light-absorbing materials for high-efficiency tandem solar cells, but their performance remains severely limited by halide phase separation. Here, we report a two-component synergistic regulation strategy based on dimethyldiamine dihydrochloride (DMACl) and lead chloride (PbCl₂) to enhance the structural stability of wide-bandgap perovskite crystals. The introduction of DMA⁺ not only stabilizes the crystal lattice by enhancing electrostatic interactions within the grains but also induces a significant bandgap blue shift, allowing the system to precisely tune the bandgap to 1.68 eV even with a significantly reduced bromine content, thereby fundamentally weakening the thermodynamic driving force for halide phase separation. Concurrently, PbCl₂ introduces Cl^- doping during the regulation of crystallization kinetics, promoting the formation of a stable alloy phase and effectively passivating halide vacancies. This synergistic regulation strategy significantly improves the film's crystallinity, extends carrier lifetime, and reduces the density of trap states. WBG perovskite solar cells fabricated using this optimized film achieved a power conversion efficiency (PCE) of 23.53%. Notably, after 1500 h of continuous maximum power point tracking (MPPT) testing under 1 sun irradiance, the unencapsulated devices retained 80% of their initial PCE.