Carrier Mobility Optimization in Thermoelectric Materials

Thermoelectric (TE) materials are functional materials that can realize the direct and reversible conversion between heat and electricity. Their conversion efficiency is determined by their average figure of merit (ZT ave). Generally, high ZT ave requires TE materials to possess both excellent electrical transport properties and low thermal conductivity, calledelectron crystal-phonon glass. To date, although commonly used band manipulation and defect designing strategies can optimize the carrier effective mass and lattice thermal conductivity, they reduce the carrier mobility and thus limit the improvement of ZT(ave). Therefore, maintaining high carrier mobility is essential for improving ZT(ave) over a wide temperature range. In this review, the methods to optimize carrier mobility, including crystal defect manipulations and multiple coupling parameter manipulations, were summarized. Specifically, crystal defect manipulations include strategies of crystal growth, crystal symmetry manipulation, and point defect manipulation, and the multiple coupling parameter manipulations include band alignment strategies, modulation doping, and band sharpening. Further, the applications of these strategies in multiple TE material systems were discussed, such as in SnSe/S, PbTe/Se/S, BiCuSeO, and BiAgSeS compounds. It was proven that the above strategies can well optimize the TE performance over the entire working temperature by effectively balancing carrier and phonon scattering and synergistically manipulating the coupling relationships between carrier mobility, effective mass, and carrier density. The importance of carrier mobility optimization in TE materials and a new research idea for developing high-efficiency TE materials were presented.

Automated summary

This review summarizes the methods to optimize carrier mobility in thermoelectric materials, including crystal defect manipulations and multiple coupling parameter manipulations, and discusses their applications in various TE material systems. The importance of carrier mobility optimization in improving TE performance over a wide temperature range is highlighted as a new research idea for developing high-efficiency TE materials.