Defect Passivation and Fermi Level Modification for >10% Evaporated All-Inorganic CsPbBr3 Perovskite Solar Cells

Current CsPbBr3 perovskite solar cells still suffer from a high open-circuit voltage (Voc) loss due to the high defect density. Herein, we demonstrate a strategy to passivate defects and induce Fermi level modification through BaI2 doping. The carrier lifetime is significantly extended after adding BaI2. In addition, the Fermi level is changed as Ba2+ enters the crystal lattice, which increases the built-in potential and promotes the transport of carriers. As a result, the optimized thermally evaporated device shows a record Voc of 1.551 V and an improved power conversion efficiency of 10.09% as well as excellent thermal stability.