Raman spectroscopic study of CdS, PVA composite films

A new material, which can be used in solar energy utilization, is obtained here by adding different weights of poly(vinyl alcohol) (PVA) to the semiconducting material CdS. The effect of this addition was studied by using FT-Raman spectrometer (based on 1500 mW Nd: YAG laser at 1064 nm), UV-Vis-IR (190-800 nm) spectrophotometer, and X-ray diffractometer. Our experimental results indicated the appearance of several new Raman bands, which have not existed in both CdS and PVA. Some of the bands which are already existing in the Raman spectra of PVA showed an unexpected systematic increase in their intensities after the addition of CdS to the matrix. On the other hand, some of the new Raman bands appeared in special concentrations of PVA only, whereas some of the Raman bands of CdS were found to disappear after adding PVA. Finally, shifts in some bands associated with random increase in their intensities after adding PVA to CdS was detected in the FT-Raman analysis. The experimental evidence given here might be attributed to the occurrence of new bonds, indicating that the produced mixture is a new material. The assignment of the new bands as well as an interpretation of the obtained variations is given here. Our X-ray diffraction data confirmed the interpretation introduced here. Moreover, the UV-Vis spectra confirmed the existence of new absorption bands in the Visible region. The IN characteristic curve was measured for a selected concentration of the new composite material, showing a remarkable increase in the values of the conduction current of about two orders of magnitude as compared with the pure PVA material. (C) 2004 Wiley Periodicals, Inc.