Stoichiometry controlled conversion efficiency in nanostructured heterojunction solar cell of CdS/CuInSXSe2−X grown by chemical ion exchange method at room temperature

Here in the present paper, we report on growth of stoichiometric and nonstoichiometric nanostructured heterojunction solar cell of CdS/CuInSXSe2–X varying X from 0 to 2 in the interval of 0.5 using cost effective, simple, chemical ion exchange method at room temperature on ITO glass substrate. The as-grown varying composition solar cells annealed at 200 °C in air and characterized for structural, compositional, optical and illumination studies. The X-ray diffraction pattern obtained from CdS/CuInSXSe2–X solar cell confirms the formation of CuInSe2, CuInS0.5Se1.5, CuInS1Se1, CuInS1.5Se0.5 and CuInS2 phases having tetragonal structure with varying crystallite size from 19, 19.37, 28, 33 and 20 nm respectively. The energy dispersive X-ray analysis (EDAX) confirms the expected elemental composition in the heterojunction solar cell. Optical absorbance analysis confirms composition controlled electronic transitions in the thin films while energy band gap observed to be red shifted with increase the value of X. The solar energy conversion efficiency achieved upon illuminating to 100 mW/cm2 observed to be 0.27%, 0.06%, 0.17%, 0.02% and 0.23% for CuInSe2, CuInS0.5Se1.5, CuInS1Se1, CuInS1.5Se0.5 and CuInS2 respectively, which correspond for stoichiometric dependent electron–hole pair generation and separation phenomenon.

► Nanostructured CdS/CuInSXSe2-X thin films can be grown using ion exchange method.
► Ion exchange method & 200 °C annealing useful for interface & surface modifications.
► Upon illuminating, conversion efficiency observed 0.27%, 0.06%, 0.17%, 0.02% & 0.23%.
► Results suggest stoichiometry controls conversion efficiency in thin film solar cells.