The structural and material properties of Cu(In,Ga)Se 2 thin films

We report on the structural and material properties of Cu-poor CuIn1-xGax Se2 (CIGS) thin films with different gallium contents grown using the co-evaporation technique. Temperature-dependent photoluminescence (PL) and high-resolution X-ray diffraction measurements were performed. The PL emission peaks observed around 1.0-1.2 eV are attributed to donor-acceptor pair luminescence. These donor-acceptor pair emissions are considered to originate from relatively shallow acceptor and donor energy levels. In addition, the X-ray diffraction spectra of the samples are simulated using a theoretical model. From the analysis, it is found that the sample with higher gallium content exhibits smaller grain size and the microstructure size uniformity is reduced. The theoretical calculation result is consistent with the experimental results derived from the PL spectra. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)