Annealing-induced changes in composition and optoelectronic properties of cadmium sulfide films used in copper–indium–gallium–diselenide solar cells

Owing to its wide band gap, cadmium sulfide film is an effective material for coating on windows when it is used with copper–indium–gallium–diselenide film. Optimizing the annealing temperature and holding time can greatly improve the composition and optical and electrical properties of cadmium sulfide film. Studies of the photoluminescence peak intensity with both a low band gap and a high band gap reveal that a higher S/Cd ratio corresponds to higher crystalline quality. This investigation analyzed two bands in the photoluminescence spectrum – one localized at 2.35–2.51 eV and the other at 1.81–1.86 eV. A cadmium sulfide sample with a highly crystalline structure was obtained by annealing at 100 °C for 20 min. The sheet carrier concentration, mobility, band gap, S/Cd ratio, and sheet resistance of the cadmium sulfide sample are −4.56 × 1016 cm−2, 20.5 cm2/V s, 2.412 eV, 0.99, and 6.67 Ω/cm2, respectively. Analysis of a performance of the obtained solar cell under standard air mass 1.5 global illumination revealed a conversion efficiency of 2.392%.

► Optimizing the annealing condition can substantially improve the properties of CdS film.
► The photoluminescence peak intensity showed that, as S/Cd ratio increased, crystalline quality increased.
► CdS sample with good crystalline structure was obtained by annealing at 100 °C for 20 min.