Oxygen-Mediated Tunability in the Physicochemical Properties of Radio-Frequency-Sputtered Vanadium Pentoxide Thin Films toward Energy Harvesting

The efficiency of a photoconversion device is presently restricted by the effectiveness of carrier extraction or contact layers. Metal oxide thin films, allowing a wide range of work function adjustability, hold promise for efficient charge extraction from light-absorbing materials. However, strict stoichiometric control remains pivotal for realizing their full potential. This study harnesses the unique attribute of ion impingement during a reactive radio-frequency (RF) sputtering technique, leading to the formation of a 2D-layered van der Waals-like structure in a room-temperature-grown amorphous vanadium pentoxide (V2O5–x) thin film by precise control of the O2 flow during growth. Moreover, the layered and phase-pure films possess the highest work function and band-gap values, rendering it highly suitable as a transparent carrier extraction layer for photovoltaic devices. An electronic transition model, comparing various spectroscopic and microscopic analyses, is proposed to correlate the seemingly contrasting trend in the band-gap and work function values as a function of the O2 flow rate and is found to depend on the degree of electronic delocalization of oxygen vacancy defects. This work adorns the crucial role of a controlled O2 flow rate in shaping both the surface and 2D-layered structure-mediated bulk properties of V2O5–x films, advancing its potential for diverse energy applications, while the adopted low-power, low-temperature growth conditions align well with the device fabrication needs.