STRUCTURAL, OPTICAL AND ELECTRICAL PROPERTIES OF CUINGASE2 (CIGS) THIN FILMS TO BE USED AS ABSORBER LAYER IN SOLAR CELLS

Abstract

Electrodeposition method is used in the present study to prepare thin films of copper indium gallium di selenide (CuInGaSe₂) using ITO coated glass substrates. Properties of CuInGaSe₂ thin films have been optimized for their potential use as an absorber layer in solar cell. Cyclic Voltameter is used to determine the reduction potentials of metals. The reduction potential value is observed in the range of 0.5 to 0.9 V. Electrodeposition process is used to prepare the five sample by varying the reduction potential applied during the process of electrodeposition. X-ray Diffraction (XRD), spectroscopic ellipsometer and Hall measurements are used to study the structural optical and electrical properties of the sample deposited on  substrate as a thin film. CuInGaSe₂ thin films, prepared and deposited at 0.5V and 0.6 V, exhibit mixed crystal phases. Whereas, single phase CuInGaSe₂ structure is observed with the increase in voltage to 0.7 V. XRD confirm the tetragonal structure of CuInGaSe₂ thin film prepared by electrodeposition process. Single phase structure persist with the further increase in voltage to 0.8V to 0.9V, however, reduced crystallite size along with increased dislocation density is observed at higher deposition voltages. Optical properties show that the electrodeposited thin films are capable to absorb maximum part of solar spectrum. The fundamental absorption edge is appeared at 1070 nm. Value of the direct band gap observed is ~1.16eV. Temperature dependent Hall measurements are performed for the thin films prepared with 0.7 V. High value of conductivity, low resistivity, high mobility and large value of carrier concentration are observed at ~315K.