Synthesis and Characterization of Cadmium Chalcogenide Semiconductor Quantum Dots Based Thin Film

Quantum dot solar cell is turned out to be the highly interesting subject of study for the next generation solar cells. The quantum dots (QDs) offer the impressive ability to harvest sunlight, beneficial features of photo stability, large molar extinction coefficients, dimension dependent optical properties and small expenses. The present work describes the synthesis and characterization of CdS chalcogenide semiconductor quantum dots. The CdS quantum dots with 6% and 10% PVA concentration were prepared by means of a sol–gel/spin coating method. The XRD studies show the amorphous nature of CdS quantum dot thin films. The HRTEM image shows the fringes of tiny dots with average sizes of 3–5 nm. The photoluminescence (PL) spectroscopy was examined with the excitation wavelength of 320 nm. The PL spectra depict a strong emission near 450 nm, corresponding to CdS band-edge emission. Raman spectra of CdS films were excited by the 632.4 nm line of an Ar ion laser. The characteristics Raman peak at 302 cm^–1 is obtained by CdS thin films, which is ascribed to CdS longitudinal optical (1LO) phonon. The CdS quantum dots follow the role of direct transition. It was observed that the optical band gap increases from 3.87 to 4.07 eV as PVA concentration increases from 6 to 10%. From dc conductivity measurement, the observed values of activation energy were found to increase from 0.89 to 1.03 with increasing PVA concentration from 6 to 10%.