Oxygen-Mediated\nTunability in the Physicochemical\nProperties of Radio-Frequency-Sputtered Vanadium Pentoxide Thin Films\ntoward Energy Harvesting

The\nefficiency of a photoconversion device is presently restricted\nby the effectiveness of carrier extraction or contact layers. Metal\noxide thin films, allowing a wide range of work function adjustability,\nhold promise for efficient charge extraction from light-absorbing\nmaterials. However, strict stoichiometric control remains pivotal\nfor realizing their full potential. This study harnesses the unique\nattribute of ion impingement during a reactive radio-frequency (RF)\nsputtering technique, leading to the formation of a 2D-layered van\nder Waals-like structure in a room-temperature-grown amorphous vanadium\npentoxide (V<sub>2</sub>O<sub>5–<i>x</i></sub>) thin\nfilm by precise control of the O<sub>2</sub> flow during growth. Moreover,\nthe layered and phase-pure films possess the highest work function\nand band-gap values, rendering it highly suitable as a transparent\ncarrier extraction layer for photovoltaic devices. An electronic transition\nmodel, comparing various spectroscopic and microscopic analyses, is\nproposed to correlate the seemingly contrasting trend in the band-gap\nand work function values as a function of the O<sub>2</sub> flow rate\nand is found to depend on the degree of electronic delocalization\nof oxygen vacancy defects. This work adorns the crucial role of a\ncontrolled O<sub>2</sub> flow rate in shaping both the surface and\n2D-layered structure-mediated bulk properties of V<sub>2</sub>O<sub>5–<i>x</i></sub> films, advancing its potential\nfor diverse energy applications, while the adopted low-power, low-temperature\ngrowth conditions align well with the device fabrication needs.