Opto-electrical characterisation of In-doped SnS thin films for photovoltaic applications

Spray pyrolised SnS thin films doped with indium were studied using various optical and electrical techniques. Structural analysis shows that all films crystallise in an orthorhombic structure with (111) as a preferential direction, without secondary phases. The doping of SnS layers with indium results in better morphology with increased grain size. Absorption measurements indicate a dominant direct transition with energy decreasing from around 1.7 eV to 1.5 eV with increased indium supply. Apart from the direct transition, an indirect one, of energy of around 1.05 eV, independent of indium doping, was identified. The photoluminescence study revealed two donors to acceptor transitions between two deep defect levels and one shallower one, with an energy of around 90 meV. The observed transitions did not depend significantly on In concentration. The conductivity measurements reveal thermal activation of conductivity with energy decreasing from around 165 meV to 145 meV with increased In content.