Scientists at the U.S. Department of Energy's National Renewable Energy Laboratory (NREL) have demonstrated a tin-lead perovskite cell that overcomes problems with stability and improves efficiency. The new cell, a tandem design with two layers of perovskites, measured a 25.5% efficiency.
source https://www.lifetechnology.com/blogs/life-technology-technology-news/new-additives-to-perovskite-tandem-solar-cells-boost-efficiency-stability
