Optical and electrochemical properties of CuInSe2 and CuInS2-CuInSe2 alloys

Abstract
The fundamental optical transitions in single crystals of CuInS2xSe22x alloys have been studied by electrolyte electroreflectance (EER) spectroscopy. The band gap of the alloys increases nonlinearly with increasing sulphur content corresponding to a bowing parameter 0.14. The flatband potential derived from the EER spectra is in excellent agreement with differential capacitance measurements and determined as −0.350 V versus the saturated calomel electrode. CuInS2xSe2−2x liquid junction solar cells are reported that exhibit a long wavelength cutoff in the spectral response matching the EER data.