Notable Performance Enhancement of CsPbI₂Br Solar Cells by a Dual-Function Strategy with CsPbBr₃ Nanocrystals

Herein, a dual-function strategy, in which CsPbI₂Br is treated by CsPbBr₃ nanocrystals (NCs) via addition and surface modification to construct the "electron bridge" and gradient heterojunction, respectively, to notably improve the performance of the CsPbI₂Br solar cells, is proposed. The "electron bridge" formed by the CsPbBr₃ NCs provides an extra transport channel for the photogenerated electrons in the CsPbI₂Br layer, thus facilitating electron transport. Meanwhile, surface modification of CsPbI₂Br by the CsPbBr₃ NCs forms a gradient heterojunction between the CsPbI₂Br layer and the P3HT layer, enhancing hole extraction accordingly. In addition, the CsPbBr₃ NC treatment passivates the defects at the bulk and surface of the CsPbI₂Br layers, thus suppressing carrier recombination. Thanks to these positive effects of the CsPbBr₃ NCs, the demonstration device with a simple configuration of ITO/SnO₂/CsPbI₂Br/P3HT/Ag achieves a notable power conversion efficiency of 17.03%, which is among the highest efficiencies reported for CsPbI₂Br-based solar cells.