Effect of annealing on photovoltaic characteristics of nanostructured p-Cu2S/n-CdS thin film

Nanostructured heterojunction solar cells of CdS/Cu2S were grown by simple chemical ion exchange reaction by immersing the CdS thin films in Cu ion solution at room temperature. The as-grown nanostructured thin films were annealed at 250 °C in air for improving the interface and crystallinity of the heterojunction. These as grown and annealed nanostructured heterojunction were characterized for photovoltaic and other optoelectronic characteristics. Increase in conversion efficiency is obtained from annealed (η = 0.24%) than the as grown heterojunction (η = 0.09%), on illuminating to 100 mW/cm2 light source. The X-ray diffraction (XRD) pattern confirms improvement in crystallinity with increase in crystallite size from 29 to 32 nm on annealing. The optical absorbance strength observed to be increased along with red shift in energy band gap value from Eg = 2.02–2.20 eV after annealing.

► Nanostructured Cu2S/CdS thin film can be prepared by chemical ion exchange route.
► 250 °C annealing improves interface, stoichiometry & morphology of Cu2S/CdS film.
► Increase in solar conversion efficiency from 0.09 to 0.24% is observed.
► Annealing improves physicochemical and optoelectronic properties of thin films.