Synergistic Effect of Methylammonium Thiocyanate and Butanammonium Formate Additives on Efficiency Enhancement in Wide-Bandgap Perovskite Solar Cells

The development of high-performance wide-bandgap perovskite solar cells (WBG PSCs) is particularly crucial for advancing tandem solar cell technology. However, the rapid crystallization of bromine-rich WBG perovskite films leads to poor film quality, which severely limits further improvements in the power conversion efficiency (PCE) and long-term stability of the PSCs. Herein, we innovatively introduced two functional additives, butanammonium formate ionic liquids (BAFA ILs) and methylammonium thiocyanate (MASCN), simultaneously into the MAPb(I 0.9 Br 0.1 ) 3 films to regulate the film crystallization dynamics and passivate vacancy defects. The introduction of volatile MASCN additives into the MAPb(I 0.9 Br 0.1 ) 3 precursor effectively improves the crystallinity and grain size of the films. Meanwhile, the introduction of BAFA ILs passivates undercoordinated Pb 2+ cation defects (halide vacancies) and undercoordinated I – /Br – anion defects (methylammonium (MA) vacancies), suppressing nonradiative recombination. Notably, when MASCN and BAFA ILs additives are introduced simultaneously, they exhibit a synergistic optimization effect. Consequently, the WBG PSCs attained a PCE of 20.54% and an open-circuit voltage ( V oc ) of 1.19 V. Meanwhile, semitransparent perovskite solar cells (ST-PSCs) were successfully fabricated, achieving a PCE of 18.61% while maintaining an average near-infrared (NIR) transmittance exceeding 80%.