Tin-based chalcogenides have a lot of potential as thermoelectric materials due to their ultralow thermal conductivity. Therefore, most reports on doped SnS focus on its power factor as the other condition for a high thermoelectric figure of merit (ZT). Here, we use the Boltzmann transport formalism to calculate both the power factor and the thermal conductivity for SnS, SnSe, and SnSxSe1−x and compare it with experimental measurements. Our theoretical model, based on a relaxation-time formalism, is in very good agreement with the reported values. We conclude that, while impurity scattering plays a major role in electron transport and, therefore, largely determines the power factor, alloy scattering is crucial for phonon transport. Specifically, alloying reduces the thermal conductivity of SnSe0.70S0.30 by a factor of ∼1.3 compared to SnSe and by a factor of ∼2 compared to SnS. This leads to ∼65% and ∼33% enhancements of ZT for p-type and n-type doping, respectively, at 800 K with respect to SnSe.

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