A Study of the Absorption Edge of CdS:In Thin Films Prepared by the Spray Pyrolysis Technique

摘要

Cadmium sulphide (CdS) is a II-VI compound with a wide band gap energy that enables it to be used as a window material in the CdTe based solar cells. In this work the absorption edge of indium doped cadmium sulphide (CdS:In) thin films was investigated. The films were prepared on glass substrates using the spray pyrolysis technique at a substrate temperature T_(s) = 490°C. X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed that the films are polycrystalline. The films displayed a wurtzite hexagonal structure with some indications of the presence of the cubic zinc blind phase. The transmittance of the films was measured at room temperature in the wavelength range 400–1100 nm and used to deduce the absorbance. The second derivative of the absorbance revealed the existence of the free exciton peaks of the wurtzite phase. The A and B free exciton peaks showed a merged peak and the C free exciton peak was apparent. These results were compared with those obtained by different authors. The separations of the aforementioned peaks were deduced and found to be in good agreement with the values found in the literature.