Tin based perovskites have been studied for almost as long as the lead based ones but they have been less efficient and much less stable. Work continues to increase their efficiency and stability, e.g.:
"Efficient tin-based perovskite solar cells with trans-isomeric fulleropyrrolidine additives" (2024-01-29)
"Efficient tin-based perovskite solar cells with trans-isomeric fulleropyrrolidine additives" (2024-01-29)
https://www.nature.com/articles/s41566-024-01381-7