Band offset of SnS solar cell structure measured by X-ray photoelectron spectroscopy

The energy band offset at the heterointerface is one of the most important properties of semiconductor heterostructures, particularly in solar photovoltaic devices. Band discontinuities of CdS/SnS and SnS/SnO₂ heterointerfaces were measured by X-ray photoelectron spectroscopy and capacitance-voltage measurements. The valence band offsets were determined to be approximately 1.5 eV for CdS/SnS and 3.5 eV for SnS/SnO₂ interfaces whereas the conduction band discontinuities for these junctions were respectively found to be 0.4 eV and 1.0 eV. Using these values and the energy band gaps of the corresponding layers, the energy band diagram was developed and it was considered to be a TYPE-II heterostructure. The Fermi level was found to be much closer to the valence band maximum for SnS, whereas it appeared in the upper half of the band gap for both CdS and SnO₂.