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. Perovskites have emerged as a highly efficient material for solar cells, but research continues to make the technology longer lasting. The new NREL cell retained 80% of its maximum efficiency after 1,500 hou...