“…Cadmium sulphide (CdS) as an important II-VI semiconductor with direct band gap of 2.42eV at room temperature is a promising candidate for solar cells, green lasers, photoconductors, light emitting diode and thin film transistors, photochemical catalysis, gas sensors, detectors for laser and infrared, display screen,nonlinear optical materials, various luminescence devices, optoelectronic devicesand so on [1,2,4,5,6,7,8,9,11,12,13,14].Optical constant as an input data in design process of the thin film devices gives the designer an additional tool for optimization of the product design, thus an accurate knowledge of optical constant over wide range of wavelength is essentially important [7].…”