The Role of Lanthanum in a Nickel Oxide-Based Inverted Perovskite Solar Cell for Efficiency and Stability Improvement

A high-performing inverted perovskite solar cell (PSC) always relies on the hole transporting layer (HTL) quality and its interfaces. This work investigates the impact of La incorporation within the NiOx matrix for defects passivation, thus leading to high charge extraction ability and stability without compromising its power conversion efficiency. In the presence of La, the La-NiOx quality is clearly improved; without the formation of pinholes. In addition, the inclusion of La alters the energy band alignment; consequently, enhancing the hole transportation and widening the V-oc (>1V), as compared to the pristine NiOx. The beneficial effect of La was further revealed through the photoluminescence measurement and density of states (DOS) analysis, in which trap states are passivated by La. More importantly, the perovskite solar cell, with La-NiOx as the HTL, exhibits 21% enhancement in efficiency and a remarkable stability that is greater than that of pristine NiOx. This also unlocks an opportunity for commercialization.