Annealing effect of absorber layer on SnS/CdS heterojunction band alignments

The effect of annealing on the physical properties of an SnS thin film and also on SnS/CdS heterojunction band alignment was studied. Vacuum annealing has greatly improved the crystalline quality of SnS and an average grain size of 1.6 μ m was achieved. Sulfur-rich secondary phases observed on the surface of as-grown SnS thin film were eliminated after vacuum annealing, resulting in a decrease of the resistivity and an increase of the carrier concentration of the film. A maximum hole mobility of 17 cm 2 V −1 s −1 was obtained for SnS thin films annealed at 400 °C. A transition of SnS/CdS heterojunction from “spike” type to “cliff” type was observed when the vacuum annealed SnS thin film was post-air-annealed at 200 and 250 °C. The band alignment of SnS/CdS heterojunction could be adjustable between “spike” type to “cliff” type via vacuum annealing followed by post-air-annealing.