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

Herein, a dual-function strategy, in which CsPbI 2 Br is treated by CsPbBr 3 nanocrystals (NCs) via addition and surface modification to construct the “electron bridge” and gradient heterojunction, respectively, to notably improve the performance of the CsPbI 2 Br solar cells, is proposed. The “electron bridge” formed by the CsPbBr 3 NCs provides an extra transport channel for the photogenerated electrons in the CsPbI 2 Br layer, thus facilitating electron transport. Meanwhile, surface modification of CsPbI 2 Br by the CsPbBr 3 NCs forms a gradient heterojunction between the CsPbI 2 Br layer and the P3HT layer, enhancing hole extraction accordingly. In addition, the CsPbBr 3 NC treatment passivates the defects at the bulk and surface of the CsPbI 2 Br layers, thus suppressing carrier recombination. Thanks to these positive effects of the CsPbBr 3 NCs, the demonstration device with a simple configuration of ITO/SnO 2 /CsPbI 2 Br/P3HT/Ag achieves a notable power conversion efficiency of 17.03%, which is among the highest efficiencies reported for CsPbI 2 Br-based solar cells.