High thermoelectric power factor in p-type Cu8GeSe6

Having a unique crystal structure with large unit cell, the decoupling of charge and phonon transport in superionic compound Cu8GeSe6 is possible for enhanced thermoelectric applications. Here, we report a promising Cu based superionic compound Cu8GeSe6 which shows a high power factor and poor thermal conductivity. The metallic charge transport and poor thermal conductivity can be understood with high carrier concentration and disordered cations via weak Cu bonds respectively. The maximum power factor value reaches 264 µWm−1K−2 at 638 K with thermoelectric figure of merit ZT∼0.3 at 623 K which is optimized for pure Cu8GeSe6.