Cyclic voltamettry (CV) studies of unitary Cu, Ga, In and Se systems, binary Cu-Se system, and quaternary Cu-In-Ga-Se have been carried out in the solutions with different concentration of sulfamic acid to understand the role of this acid as a complexing agent. Cu(InGa)Se2 (CIGS) thin films were deposited on Mo/soda-lime glass substrates by electrodeposition in the same applied potential and the same electrotyle bath but different in concentration of sulfamic acid, from 0 mM to 40 mM. The composition of the films was determined by EDS. The crystalline structure and morphology of the films were characterized by XRD and SEM, respectively. The obtained results indicate that sulfamic acid with an appropriate concentration (about 20-30 mM) can inhibit the underpotential deposition of Cu-Se phases and the H+ reduction into H2 which are considered as the undesired process. On the other hand, sulfamic acid can promote the reduction of Ga3+, consequently can increase the Ga concentration. The desired Cu(In0.70Ga0.30)Se2 stoichiometry was obtained in the films grown from solution which contains 20-30 mM sulfamic acid.

Keywords: CIGS, Electrodeposition, Complexing agent, Thin film, Solar cell