Effects of sulphur and air annealing on the properties of thermally evaporated SnS layers for application in thin film solar cell devices

Thin films of tin sulphide (SnS) have been deposited using the thermal evaporation method and the layers annealed in either air or an environment containing elemental sulphur to increase the grain size while minimising sulphur loss from the annealed layers. Scanning electron microscopy (SEM), X-ray diffractometer (XRD) and optical data are given for the as-deposited and annealed samples. Heterojunction devices were made with CdS as the n-type partner layer in the “superstrate configuration.” The spectral response of these devices exhibited the classic “heterojunction window effect.” Capacitance-voltage measurements indicated uniform doping of the SnS for low reverse biases (<0.5 V) with a carrier concentration 10¹⁴ - 10¹⁵cm^-3 near to the junction and a built-in voltage of 0.85 V. Capacitance frequency measurements corresponded to an interface trap density of 3.06 x 10¹¹FC^-1cm^-2.