Multifunctional Regulation of Highly Orientated Tin–Lead Alloyed Perovskite Solar Cells

Tin–lead (Sn–Pb) alloyed perovskites are promising candidates for next-generation photovoltaics due to their appropriate bandgaps for multijunction tandem solar cells, which can potentially overcome the Shockley-Queisser limit. However, their power conversion efficiency (PCE) and stability are still impeded by the poor absorber quality and defects caused by the oxidation of Sn2+. Here, we introduced trimethylsulfoxonium iodide (TMSI) as an additive along with SnF2 to fabricate Sn–Pb perovskite films with enlarged grains and improved film quality. TMSI restrained the oxidation of Sn2+ through molecular interactions, reducing the formation of detrimental Sn vacancies. As a result, a highly oriented Sn–Pb alloyed perovskite with a lower defect density was obtained, along with suppressed ion migration. The TMSI-treated Sn–Pb-based devices exhibited a champion PCE of 22.6% and outstanding stability, retaining 83% of their original efficiency after 6000 h of storage under a N2 atmosphere and maintaining 88% of their initial value after 1200 h of continuous one-sun illumination.