Improvement of minority-carrier lifetime in tin monosulfide via substrate engineering

Tin (II) monosulfide (SnS) is a promising Earthabundant, non-toxic thin-film absorber due to its near-ideal optoelectronic properties and manufacturability, but low minority-carrier lifetimes limit SnS device efficiencies to below 5%. We employ electron beam-induced current measurements to deduce the effect of structural defects on bulk recombination in our champion thermally evaporated devices, and then use graphene substrates as a means to reduce detrimental structural defects. We demonstrate an improvement in the effective minority-carrier lifetime of SnS using a graphene substrate, suggesting that the use of substrates with van der Waals surface termination may provide a route toward higher-efficiency SnS-based devices.