Energy Band Alignment of ZnS_xSe_(1-x) Films on Si for Photovoltaic Carrier-Selective Contacts

ZnS_xSe_(1-x) films are promising materials for front carrier-selective contacts in silicon photovoltaics given their wide bandgaps and low resistivities compared to amorphous silicon. Xray photoelectron spectra of ZnS_xSe_(1-x) (x ranging from 0 to 1) films grown on Si by molecular beam epitaxy were used to measure band offsets of ZnS_xSe_(1-x) with respect to Si for purposes of accurate optoelectronic simulations of photovoltaic devices incorporating ZnS_xSe_(1-x) carrier-selective contacts. Conduction band offsets ranged from 0.68 eV (x = 0) to 1.52 eV (x = 1) showing a significant departure from both Anderson model and density functional theory predictions.