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Preprints Archive: Abstract of IC2010008 (2010)
Deposition of single-phase Cu(In,Ga)Se_2 thin films from the selenization of thermally evaporated InSe/Cu/GaSe precursors
Document info: Pages 12, Figures 5.
The relatively small band gap values (~1eV) of CuInSe2 thin films limits the conversion efficiencies of completed CuInSe_2/CdS/ZnO solar cell devices. In the case of traditional two-stage growth techniques, limited success has been achieved to homogeneously increase the band gap by substituting indium with gallium. In this study, thermal evaporation of InSe/Cu/Gase precursors were exposed to an elemental Se vapour under defined conditions. This technique produced large-grained, single-phase Cu(In,Ga)Se_2 thin films with a high degree of in-depth compositional uniformity. The selenization temperature, ramp time, reaction period and the effusion cell temperature with respect to the Cu(In,Ga)Se_2 films were optimized in this study. The homogeneous incorporation of Ga into CuInSe_2 led to a systematic shift in the lattice spacing parameters and band gap of the absorber films. Under optimized conditions, gallium in-cooperation resulted only in a marginal decrease in the grain size, X-ray diffraction studies confirmed single-phase Cu(In,Ga)Se_2 material and X-ray photoluminescence spectroscopy in-depth profiling revealed a uniform distribution of the elements through the entire depth of the alloy. From these studies optimum selenization conditions were determined for the deposition of homogeneous Cu(In,Ga)Se_2 thin films with optimum band gap values between 1.01 and 1.21 eV.