Photoelectrochemical performance of gallium-doped AgInS2 photoelectrodes prepared by electrodeposition process

Gallium-doped silver–indium–sulfide (Ga-doped AgInS2) samples were deposited onto fluorine-doped-tin-oxide (FTO) glass substrates using a one-step electrodeposition method. The effect of the [Ga]/[In] molar ratio in the solution bath on the structure, morphology, and photoelectrochemical (PEC) properties of samples is reported. X-ray diffraction (XRD) patterns of samples reveal that the peaks of samples shifted to higher angles with increasing [Ga]/[In] ratio in the solution bath. The thickness, direct band gap, and indirect band gap of the samples were in the ranges of 643–580 nm, 1.84 eV–1.93 eV, and 1.42–1.59 eV, respectively. The flat-band potentials of the films were in the range from –0.76 to –0.99 V vs. a normal hydrogen electrode (NHE), as obtained using Mott–Schottky plots and open-circuit potential (OCP) measurements of samples. The maximum photoenhancement current density (10.37±0.13 mA cm−2) was obtained for Ga-doped AgInS2 films with a precursor ratio of [Ga]/[In]=0.03 at an applied bias of +1.0 V vs. Ag/AgCl electrode in K2SO3 (0.25 M) and Na2S (0.35 M) aqueous solution. Results show that high-quality Ga-doped AgInS2 thin films can be deposited on FTO glass using one-step electrodeposition for PEC applications. Stability test of the AgInS2 thin films in aqueous solution is also reported in this study.