Ternary Ag-In-S polycrystalline films deposited using chemical bath deposition for photoelectrochemical applications

This paper describes the preparation and characterization of ternary Ag-In-S thin films deposited on indium tin oxide (ITO)-coated glass substrates using chemical bath deposition (CBD). The composition of the thin films was varied by changing the concentration ratio of [Ag]/[In] in the precursor solutions. The crystal structure, optical properties, and surface morphology of the thin films were analyzed by grazing incidence X-ray diffraction (GIXRD), UV-vis spectroscopy, and field-emission scanning electron microscopy (FE-SEM). GIXRD results indicate that the samples consisted of AgInS₂ and/or AgIn₅S₈ crystal phases, depending on the composition of the precursor solutions. The film thicknesses, electrical resistivity, flat band potentials, and band gaps of the samples were between 1.12 and 1.37 μm, 3.73 × 10^-3 and 4.98 × 10⁴ Ω cm, -0.67 and -0.90 V vs. NHE, and 1.83 and 1.92 eV, respectively. The highest photocurrent density was observed in the sample with [Ag]/[In] = 4. A photocurrent density of 9.7 mA cm^-2 was obtained with an applied potential of 0.25 V vs. SCE in the three-electrode system. The photoresponse experiments were conducted in 0.25 M K₂SO₃ and 0.35 M Na₂S aqueous electrolyte solutions under irradiation by a 300 W Xe light (100 mW cm^-2). The results show that ternary Ag-In-S thin film electrodes have potential in water splitting applications.