Aqueous precipitation and electrical properties of In2S3: characterization of the In2S3/polyaniline and In2S3/ polypyrrole heterojunctions

Article abstract of DOI:10.1007/BF00367815

The stability of indium sulphide aqueous supersaturated solutions at pH 2.50 and 25°C was investigated. Spontaneous precipitation proceeded at rates proportional to the solution supersaturation via a polynuclear mechanism and the phase formed was identified as In₂S₃. The absorption spectrum of In₂S₃ was measured from 190-800 nm and from the absorption threshold the optical energy gap was estimated to be E_o=(1.8±0.1) eV. The thermal energy gap E_t=(1.6±0.2) eV was determined from resistivity against temperature measurements and a thermopower coefficient S=-100μVK^-1 at room temperature was found. Finally, In₂S₃/polyaniline and In₂S₃/ polypyrrole heterojunctions were prepared and from the investigation of their I-V characteristics, the values of the ideality factor, n, the saturation current density, J_o, and the effective barrier height, φ_B, were determined to be n=(15±2), J_o=(38±7) A m^-2 and φ_B=0.56 eV for the polyaniline and n=(64±8), J_o=(13±2) A m^-2 and φ_B=0.59 eV for the polypyrrole heterojunction.