Lone conduction band in Cu2ZnSnSe4

We present experimental proof for a narrow first conduction band in Cu2ZnSnSe4 semiconductor films as it has been predicted by theoretical calculations. The optical absorption characteristics of Cu2ZnSnSe4 thin films are analyzed by optical transmission spectroscopy. The experimental data show strong evidence for three absorption edges, as expected from theory, involving the valence band and two conduction bands, which are separated by a second band gap. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3691945]