Real-time analysis of the microstructural evolution and optical properties of Cu(In,Ga)Se2 thin films as a function of Cu content

Thin films of Cu(In,Ga)Se-2 with various copper contents were deposited by co-evaporation onto thermally oxidized silicon substrates. Characterization by real-time spectroscopic ellipsometry reveals clear similarities among the samples, as well as key variations with Cu content. Although all films exhibit a Volmer-Weber nucleation and similar fundamental critical point energies in the analysis of optical properties, Cu-rich films exhibit enhanced coalescence, smoother surfaces, larger grain sizes, as well as a sub-bandgap absorption which is absent in Cu-poor films. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim