Synergistic Effect of Codoped Nickel Oxide Hole–Transporting Layers for Highly Efficient Inverted Perovskite Solar Cells

摘要

Inverted perovskite solar cells (PSCs), which feature an attractive structure fordiverse applications such as tandem SCs or flexible devices, continue to berapidly developed. Among various hole-transporting layer (HTL) materials, nickelO_xide (NiO_x) is widely used as a stable and superior HTL even though it exhibitspoor conductivity. Although various methods have been proposed to overcomethe low conductivity of NiO_x films, codoping methods have not been extensivelystudied and remain poorly understood. Herein, Li:Cu:NiO_x is systematicallyinvestigated to explore the synergistic effect of codoping in various NiO_x HTLsand PSCs. The optical, chemical, and morphological properties of the films arecharacterized and the dependence of these properties on the codoping ratio areinvestigated. A gradual improvement of the electrical properties and a tunableFermi energy level resulting from the Li:Cu codopants is subsequently demonstrated.Furthermore, the structure of the perovskite films on HTLs and thesynergistic effect on the preferred crystal growth behavior are elucidated. Aninverted PSC with high efficiency was attained as a result of the enhancedelectrical properties of the NiO_x HTLs and the high quality of the perovskite film,which were attributed to the synergistic effect of the Li:Cu codoping method.