Effect of Co doping on CIS2 thin films

Abstract

In recent years, substantial scientific attention has been focused on renewable energy resources, which utilize natural resources for the production of electrical energy. Chalcopyrite semiconductors are used as one of the alternatives, Cu(In,Ga)Se2 (CIGS) and CuInS2 (CIS) are used for the fabrication of solar cells. These materials possess various properties Viz. ideal band gap (1.5 eV), high optical absorption, low light degradation, high radiation resistance, etc., hence they are suitable in the fabrication of solar cells. In contrast to other chalcopyrates, CuInS2 is nontoxic, low-cost and easy to prepare by simple deposition techniques. Several impurities were doped to CuInS2 bulks, to control conduction and also to obtain low resistivity. In this context, the structural, morphological and optical properties are reported for cobalt-doped CuInS2 (CIS2) thin films prepared by electro-deposition technique at room temperature. In the present study, we have used different cobalt concentration in the range of 0–5 wt.%. Doping of cobalt does not lead to the formation of any secondary phase, either in the form of metallic clusters or impurity complexes. However, with increase in cobalt concentration a decrease in the optical band gap, from 2.10 to 1.53 eV, is observed. In addition, implantation of cobalt in the CIS2 gave changes in structural and surface properties of the thin films obtained. These thin films are also subjected to elemental analysis using EDAX.