Deposition and characteristics of bismuth sulfide thin films by an in situ chemical reaction process at room temperature: a facile and eco-friendly approach

Uniform, smooth and densely packed Bi₂S₃ thin films were prepared at room temperature by an in situ solution chemical reaction using bismuth nitrate as precursor in a form of thin solid film which was reacted with ammonium sulfide ethanol solution. Bi₂S₃ thin films both as-deposited and annealed at different temperatures were characterized by XRD, SEM, EDS, AFM, UV–Vis–NIR and LSV measurements. The thin films growth with deposition cycle numbers was investigated. The results showed that the as-deposited Bi₂S₃ thin films were almost amorphous and near to chemical stoichiometry. The annealing promoted crystallization to orthorhombic structure as well as crystal growth from very small particles to short-rod shaped nanocrystals. The optical band-gap energy was in the range of 1.34–1.69 eV depended on crystal size on films. The eight dip-cycles Bi₂S₃ films annealed at 300 °C had a better photoelectrochemical performance with photocurrent density of 5.03 mA/cm² bias 0.5 V vs. Ag/AgCl reference electrode. This in situ deposition had an average deposited rate of 40 nm per cycle and a self-perfect function to grow smooth with increase of dip-cycle numbers.