High thermoelectric performance and compatibility in Cu3SbSe4–CuAlS2 composites

Developing a non-toxic tellurium-free alternative for PbTe is crucial for large-scale waste heat recovery. Here we demonstrate that a simple Cu3SbSe4–CuAlS2 composite can reach a peak zT of 1.8 and an average zT of 0.77 in the temperature range of 300–723 K, both of which are the record-high values in diamond-like semiconductors. Experimental transport data and X-ray absorption fine structure spectroscopy analysis suggest that the significantly enhanced electrical performance mainly originates from the diminished carrier scattering deformation potential. More importantly, Cu3SbSe4–CuAlS2 composites exhibit a weak temperature dependence of compatibility, making it superior to most IV–VI thermoelectric compounds from the aspect of device fabrication. Meanwhile, both the thermal stability and mechanical performance of Cu3SbSe4 are improved by CuAlS2 compositing. Our findings reveal that the Cu3SbSe4-based composite made of environmental-friendly and earth-abundant elements can be comparable to p-type PbTe in middle-temperature thermoelectric power generation.