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(I0.9Br0.1)3 films to regulate the film crystallization dynamics and passivate vacancy defects. The introduction of volatile MASCN additives into the MAPb(I0.9Br0.1)3 precursor effectively improves the crystallinity and grain size of the films. Meanwhile, the introduction of BAFA ILs passivates undercoordinated Pb2+ 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 (Voc) 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%.