Enhancement of thermoelectric figure of merit by pressure-driven electronic topological transition

The world is currently facing a state of energy shortage, and thus the alternative green energy is ultimately in demand. Thermoelectric generators, which can generate electricity directly from waste heat with the advantages of reliability and compactness, are considered as potential devices for waste heat recovery. The thermoelectric performance is usually evaluated by a parameter named as the figure of merit zT. So far, the maximum zT at room temperature has remained around 1.0 over sixty years. For practical technological applications, it is highly desired to break this barrier. Here, we choose a Cr doped PbSe with the maximum zT less than 1.0 at high temperature of about 700 K. By simply applying external pressure, we obtain the record high zT value of 1.74 at room temperature. Pressure-driven electronic topological transition is proposed to account for such a huge enhancement. These results and findings point to a new direction in the improvement of zT in the existing thermoelectric materials through the lattice compression.