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 CrO_x-based hole-transport material has been introduced. The feasibility of fabrication efficient perovskite solar cells with CrO_x and Cu-CrO_x 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 CrO_x film, which can increase work function, electrical conductivity, and carrier mobility of the CrO_x 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.