A Novel Anion Doping for Stable CsPbI 2 Br Perovskite Solar Cells with an Efficiency of 15.56% and an Open Circuit Voltage of 1.30 V

The Cs‐based inorganic perovskite solar cells (PSCs), such as CsPbI 2 Br, have made a striking breakthrough with power conversion efficiency (PCE) over 16% and potential to be used as top cells for tandem devices. Herein, I − is partially replaced with the acetate anion (Ac − ) in the CsPbI 2 Br framework, producing multiple benefits. The Ac − doping can change the morphology, electronic properties, and band structure of the host CsPbI 2 Br film. The obtained CsPbI 2− x Br(Ac) x perovskite films present lower trap densities, longer carrier lifetimes, and fast charge transportation compared to the host CsPbI 2 Br films. Interestingly, the CsPbI 2− x Br(Ac) x PSCs exhibit a maximum PCE of 15.56% and an ultrahigh open circuit voltage ( V oc ) of 1.30 V without sacrificing photocurrent. Notably, such a remarkable V oc is among the highest values of the previously reported CsPbI 2 Br PSCs, while the PCE far exceeds all of them. In addition, the obtained CsPbI 2− x Br(Ac) x PSCs exhibit high reproducibility and good stability. The stable CsPbI 2− x Br(Ac) x PSCs with high V oc and PCE are desirable for tandem solar cell applications.