Unveiling the defect levels in SnS thin films for photovoltaic applications using photoluminescence technique

Exploiting the potential of the material for the photovoltaic applications requires an extensive defect level analysis, mandatory. Photoluminescence (PL) technique was employed to probe the defect levels in p-SnS thin films deposited using chemical spray pyrolysis (CSP) technique. Three PL emissions were recorded at 1.09, 0.76, and 0.75 eV. Systematic investigations performed, focusing the 1.09 eV emission, revealed that the shoulder at 1.093 eV gets completely quenched beyond 110K. From this study, we could identify a bound exciton associated to a shallow donor level whose activation energy was calculated to be 20 meV from Arrhenius plot. By studying the variation of PL intensity with excitation power, we could zero-in that the emission at 1.09 eV was a donor acceptor pair (DAP) transition. Knowing the band gap to be 1.33 eV, we could identify a deep acceptor at 0.22 eV above valence band. The band structure deduced from the present analysis is depicted in the abstract figure.