CaI2: a more effective passivator of perovskite films than PbI2 for high efficiency and long-term stability of perovskite solar cells

Much less additive content of 0.5% CaI₂ instead of 5% PbI₂ was incorporated into the CH₃NH₃PbI₃ film and a dense and surface-smooth morphology was obtained with much enlarged crystal grains. The champion PSC based on MAPbI₃(CaI₂)_0.005 layer demonstrated a very high PCE of 19.3% with superior long-term stability.