Structural and compositional properties of Cu(In,Ga)Se2 thin films prepared by the thermal evaporation of compound materials

In this study, device quality chalcopyrite thin films were prepared by the thermal evaporation of pulverized compound materials from a single crucible. The starting materials were heated from ambient temperature to around 1450degreesC over a period of only 10 min. This 'semi-flash' process prevented many of the reported shortcomings of standard flash processes. The final thicknesses and compositions of the chalcopyrite thin films were determined by the predetermined masses of the starting materials. The material quality (i.e. surface morphologies, formation of crystalline phases and in-depth compositional uniformity) of the films was evaluated at substrate temperatures ranging between 250degreesC and 500degreesC. From these studies, optimum growth conditions were determined for the deposition of device quality absorber material. The conversion efficiencies of completed glass/Mo/Cu(In,Ga)Se-2/CdS/ZnO solar cell devices were correlated against the material quality of the respective absorber films.