A Novel Anion Doping for Stable CsPbI2Br 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 CsPbI2Br, 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 CsPbI2Br framework, producing multiple benefits. The Ac- doping can change the morphology, electronic properties, and band structure of the host CsPbI2Br film. The obtained CsPbI2-xBr(Ac)(x) perovskite films present lower trap densities, longer carrier lifetimes, and fast charge transportation compared to the host CsPbI2Br films. Interestingly, the CsPbI2-xBr(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 CsPbI2Br PSCs, while the PCE far exceeds all of them. In addition, the obtained CsPbI2-xBr(Ac)(x) PSCs exhibit high reproducibility and good stability. The stable CsPbI2-xBr(Ac)(x) PSCs with high V-oc and PCE are desirable for tandem solar cell applications.