Effects of annealing conditions and temperatures on sputtered NiOx thin films for perovskite solar cells

This study focuses on optimizing direct current, reactively sputtered nickel oxide (NiOx) as a hole transport layer (HTL) for perovskite solar cells (PSCs). By employing reactively sputtered NiOx instead of spin-coated NiOx, the redox reaction between the HTL and the perovskite layer in PSCs was minimized. Additionally, the study examines the impact of different annealing conditions on the oxidation state of NiOx HTL and its effect on PSC performance. X-ray diffraction analysis revealed that a higher oxygen flow rate and lower deposition rate resulted in a more continuous film with enhanced crystallinity. X-ray photoelectron spectroscopy further indicated that Ni2+ ion concentration increased with atmospheric and high-temperature annealing. By systematically optimizing sputtering parameters and annealing conditions, the power conversion efficiency of PSCs was significantly improved from 5% to 13.5%, highlighting the importance of controlling the oxidation state of NiOx HTL to enhance PSC performance.