Taking in more sun: Most efforts to grow superior films of organic-inorganic perovskites for solar cells have focused on methylammonium lead iodide (MAPbI ₃ ). However, formamidinium lead iodide (FAPbI ₃ ) has a broader solar absorption spectrum that could ultimately lead to better performance. Yang et al. grew high-quality FAPbI ₃ films by starting with a film of lead iodide and dimethylsulfoxide (DMSO) and then exchanging the DMSO with formamidinium iodide. Their best devices achieved power conversion efficiencies exceeding 20%. Science , this issue p. 1234

Healing defects with triiodide ions: Deep-level defects in organic-inorganic perovskites decrease the performance of solar cells through unproductive recombination of charge carriers. Yang et al. show that introducing additional triiodide ions during the formation of layers of formamidinium lead iodide, which also contain small amounts of methylammonium lead bromide, suppresses the formation of deep-level defects. This process boosts the certified efficiency of 1-cm ² solar cells to almost 20%. Science , this issue p. 1376