We investigated the dependence of absolute SnS band-edge energies on surface orientation using density functional theory and GW method for all surfaces with Miller indices 3h,k,l3 and found variations as large as 0.9 eV as a function of (hkl). Variations of this magnitude may affect significantly the performance of photovoltaic devices based on polycrystalline SnS thin-films and, in particular, may contribute to the relatively low measured open circuit voltage of SnS solar cells. X-ray diffraction measurements confirm that our thermally evaporated SnS films exhibit a wide distribution of different grain orientations, and the results of Kelvin force microscopy support the theoretically predicted variations of the absolute band-edge energies.

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See supplementary material at http://dx.doi.org/10.1063/1.4879558 for the detailed description of Kelvin force microscopy.

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