Band alignment at the Cu2ZnSn(SxSe1-x)(4)/CdS interface

Abstract

Energy band alignments between CdS and Cu2ZnSn(SxSe1-x)(4) (CZTSSe) grown via solution-based and vacuum-based deposition routes were studied as a function of the [S]/[S+Se] ratio with femtosecond laser ultraviolet photoelectron spectroscopy, photoluminescence, medium energy ion scattering, and secondary ion mass spectrometry. Band bending in the underlying CZTSSe layer was measured via pump/probe photovoltage shifts of the photoelectron spectra and offsets were determined with photoemission under flat band conditions. Increasing the S content of the CZTSSe films produces a valence edge shift to higher binding energy and increases the CZTSSe band gap. In all cases, the CdS conduction band offsets were spikes. (C) 2011 American Institute of Physics. [doi:10.1063/1.3600776]