Copper-Doped Chromium Oxide Hole-Transporting Layer for Perovskite Solar Cells: Interface Engineering and Performance Improvement

To achieve high performance for inverted structure perovskite solar cells, the design of hole-transporting layer (HTL) and related interfacial engineering are very important tasks. To avoid the hygroscopic characteristics of poly (3, 4-ethylenedioxythiophene):poly (styrenesulfonate) that may degrade the adjacent moisture-sensitive perovskite layer, here, a new CrOx-based hole-transport material has been introduced. The feasibility of fabrication efficient perovskite solar cells with CrOx and Cu-CrOx as HTLs is confirmed for the first time. Cu doping can modify the chromium ion contents and suppress the formation of surface hydroxylation and CrO3 in the CrOx film, which can increase work function, electrical conductivity, and carrier mobility of the CrOx films. Consequently, the power conversion efficiency of the corresponding device increases to 10.99% from its original value of 9.27%. This study not only provides a novel HTL system for high performance and decently stable optoelectronic devices but also reveals the importance of HTL doping for interface engineering.