Influence of anionic substitution on the electrolyte electroreflectance study of band edge transitions in single crystal Cu2ZnSn(SxSe1−x)4 solid solutions

Single crystals of Cu2ZnSn(SxSe1−x)4 (CZTSSe) solid solutions were grown by chemical vapor transport technique using iodine trichloride as a transport agent. As confirmed by X-ray investigations, the as-grown CZTSSe solid solutions are single phase and crystallized in kesterite structure. The lattice parameters of CZTSSe were determined and the S contents of the obtained crystals were estimated by Vegard’s law. The composition dependent band gaps of CZTSSe solid solutions were studied by electrolyte electroreflectance (EER) measurements at room temperature. From a detailed lineshape fit of the EER spectra, the band gaps of CZTSSe were determined accurately and were found to decrease almost linearly with the increase of Se content, which agreed well with the recent theoretical first-principle calculations by S. Chen, A. Walsh, J.H. Yang, X.G. Gong, L. Sun, P. X. Yang, J.H. Chu, S.H. Wei, Phys. Rev. B 83 (2011) 125201 (5pp).

► Growth of Cu2ZnSn(SxSe1−x)4 single crystals by chemical vapor transport method.
► Electrolyte electroreflectance study of Cu2ZnSn(SxSe1−x)4 were performed at 300 K.
► Band gaps of Cu2ZnSn(SxSe1−x)4 were obtained by lineshape fits of the EER spectra.
► Band gaps of Cu2ZnSn(SxSe1−x)4 were decreased almost linearly with the Se content.