Buried Interface Passivation with Butylammonium Methyl Sulfonate for High-Performance Inverted Wide-Band Gap Perovskite Solar Cells

The efficiency and stability of wide-band gap perovskite solar cells (PSCs) are primarily constrained by photoinduced halide segregation and interfacial defects. Here, it is shown that the butylammonium methyl sulfonate contains a positively charged ammonium group, a negatively charged sulfonic group, and a long alkyl chain and plays multiple roles in passivating the grain boundary defects at the buried interface, mitigating nonradiative recombination, and reducing the defect state density. The optimized inverted PSCs with a 1.7 eV band gap demonstrated an excellent efficiency of 21.17% and retained 83% of their initial efficiency after being stored in a glovebox for 49 days without encapsulation.