Photoelectrochemical\nProperties of CuFeO<sub>2</sub> Photocathodes Prepared by Pulsed Laser\nDeposition

Photoelectrochemical\n(PEC) water splitting using tandem\ncell devices\noffers a promising method for generating green hydrogen from solar\nenergy. Developing suitable semiconductor materials is crucial for\nthe cost-effectiveness and scalability of this technology. CuFeO<sub>2</sub> has gained attention due to its narrow bandgap, positive\nphotocurrent onset potential, and earth-abundant nontoxic composition.\nHowever, CuFeO<sub>2</sub> photocathode performance is hindered by\nweak catalytic activity, Fermi level pinning, bulk defect states,\nand charge carrier localization. In this work, we employ pulsed laser\ndeposition (PLD) to produce high-purity CuFeO<sub>2</sub> thin films\nwith controlled morphology and crystal structure. We optimize the\nparameters for the PLD process to produce compact and uniform films,\nminimizing diffuse optical scattering. By doing so, we can accurately\ndetermine the absorption coefficient, as well as the direct and indirect\nband gaps of the films. Our study provides important insights into\nthe carrier dynamics in CuFeO<sub>2</sub> thin films, including localization\nin the picosecond and nanosecond time scales. Important electrical\nproperties such as the dielectric constant and the flat-band potential\nare identified. Surface chemical states are elucidated by detailed\nX-ray photoelectron spectroscopy analyses. In addition, photoelectrochemical\ntests show promising potential for these films in water splitting.\nThese findings highlight key properties and improvement opportunities\nfor CuFeO<sub>2</sub> films for photoelectrochemical applications.