Cu2SnS3 is a promising low-cost and eco-friendly thermoelectric material. However, its rigid diamond crystal structure leads to a high thermal conductivity and hence its overall poor thermoelectric properties. Here we show Ni doping at the Sn site can introduce a dense dislocation of density of ∼4.83 × 109 cm-2 to Cu2SnS3. The abundant dislocations generate a large strain within the matrix, which effectively scatters heat-carrying phonons. The resultant lowest κlatt reaches ∼0.41 W m-1 K-1 at 723 K, approaching the theoretical limit (0.30 W m-1 K-1). The regulation strategy on dislocations is expected to reduce the thermal conductivity and improve the functionalities of other diamond-like materials.
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