Photoconductivity in sprayed β-In2S3 thin films under sub-band-gap excitation of 1.96 eV

beta-In2S3 thin films with a band gap of similar to 2.67 eV exhibited persistent photoconductivity when excited using photons with energy of 1.96 eV. The photoconductive response to extrinsic photoexcitation could be removed when the film stoichiometry was changed. Photoluminescence studies in the films revealed an emission of 1.826 eV, due to donor-acceptor pair (DAP) recombination, which was absent in the film not responding to extrinsic excitation. Hence, it was concluded that presence of the DAP was responsible for the extrinsic photoconductivity under the 1.96 eV excitation. This study can initiate further a methodology for tailoring the photoresponse of this semiconducting thin film by spatially controlling the film stoichiometry.