Preparation of Cu(In,Ga)S2 Thin Film for Photovoltaic Application by Annealing of Electrodeposited Cu-Ga-S Precursor from Alcohol Solution

Abstract

A new synthetic route for Cu(In,Ga)S2 (CIGS) absorber thin film is presented. It involves the one-step electrodeposition of Cu-Ga-S precursors on indium tin oxide (ITO) substrate from alcohol solution followed by thermal annealing treatment to incorporate In, diffused from the ITO substrate. Several characterization methods including XRD, SEM, EDS, TEM and absorption spectra are used to characterize the synthesized quaternary Cu(In,Ga)S2 (CIGS). Pure quarternary chalcopyrite Cu(In,Ga)S2 (CIGS) phase in good polycrysralline structure without secondary phase is obtained after annealing. The influence of deposition potential on the morphology and optical properties of the films is investigated. A relative positive deposition potential results in a larger crystalline size benefitting the photoelectrical conversion. A possible growth mechanism for explaining the formation of Cu(In,Ga)S2 (CIGS) thin films is proposed and briefly discussed. The electrochemical photoresponse of the Cu(In,Ga)S2 (CIGS) thin films indicating a p-type semiconductor implies its potential application in photovoltaic devices.