Preparation of CuInSe2 thin films by spin-coating and selenization

In order to fabricate low cost and printable CuInSe2 (CIS) thin film solar cells, a chemical process has been developed to fabricate uniform CIS films with large grain size and close stoichiometry to chalcopyrite phase. Cu(NO3)2, InCl3 and ethyl cellulose (EC) were adopted to form the starting solution. CIS films were prepared by spin-coating and selenization. Precursor films and CIS films were investigated by SEM, EDS and XRD. CuCl and InCl3 crystals appeared in the precursor films. During the selenization process, CuCl first reacted with Se vapor to form Cu2-xSe. With increasing selenization temperature, InCl3 reacted with Cu2-xSe to form CIS accompanying the evaporation of chlorine in the form of gas. It is revealed that the element ratio in final CIS film is determined by the raw material ratio in the starting solution and the selenization temperature.