Study of the optimal condition for electroplating of Bi2S3 thin films and their photoelectrochemical characteristics

Bismuth sulfide (Bi₂S₃) thin films were electrodeposited from non-aqueous dimethyl sulfoxide medium containing Bi(NO₃)₃ and thiourea as the precursor salts, triethanol amine as the complexing agent, and TritonX-100 as the surface active agent. The prepared films were subjected to rigorous experimentation in order to validate their potential candidature for solar cells. The films exhibited band gap energy of ∼1.3 eV and resistivity of the order of 2 × 10⁶ Ω cm at room temperature as was obtained from UV–Vis spectroscopy and four-probe measurements, respectively. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and energy dispersive analysis of X-ray were employed to reveal the morphology, structure, and chemical composition of the film matrix. The Bi₂S₃ films were found to be non-decomposable up to the temperature of 1,000 °C with the help of thermogravimetry–differential thermal analysis. The Nyquist and Mott–Schottky plots derived from electrochemical impedance spectroscopy measurements provided important information regarding electrical and semiconducting properties of the films. The n-type film with a donor density of the order of ∼10²³ m⁻³ displayed reasonable photoactivity under illumination and is recommended as a promising candidate for potential photoelectrochemical applications.