Interfacial band offset engineering with barium-doping towards enhanced performance of all inorganic CsPbI 2 Br perovskite solar cells.

This study investigates the incorporation of Ba 2+ at a low concentration into CsPbI 2 Br, resulting in the formation of mixed CsPb 1- x Ba x I 2 Br perovskite films. Photovoltaic devices utilizing these Ba-doped CsPbI 2 Br (Ba-CsPbI 2 Br) perovskite films achieved a higher stabilized power conversion efficiency of 14.07% compared to 11.60% for pure CsPbI 2 Br films. First-principles density functional theory calculations indicate that the improved device performance can be attributed to the efficient transport of conduction electrons across the interface between Ba-CsPbI 2 Br and the TiO 2 electron transporting layer (ETL). The Ba-CsPbI 2 Br/TiO 2 interface exhibits a type-II staggered band alignment with a smaller conduction band offset (CBO) of 0.25 eV, in contrast to the CsPbI 2 Br/TiO 2 interface with a CBO of 0.48 eV. The reduced CBO at the Ba-CsPbI 2 Br/TiO 2 interface diminishes the barrier for conduction electrons to transfer from the Ba-CsPbI 2 Br layer to the TiO 2 layer, facilitating efficient charge transport.