We studied the effect of doping with Bi on the thermoelectric properties of SnTe-based materials. Doping with Bi reduced the density of holes and increased the Seebeck coefficient over a wide temperature range as a result of modulation of the carrier concentration and an increase in the density of states effective mass. The lattice thermal conductivity was also greatly reduced as a result of the wide frequency range of phonon scattering by multiscale architectures derived from Bi doping. A maximum ZT value of c. 1.1 at 873 K was obtained in Sn_0.94Bi_0.06Te, an enhancement of 165% compared with the undoped sample.

Thermoelectrics can recover waste heat, environmental heat or heats from different sources and convert it to electricity. Inorganic or metal thermoelectrics have higher ZT values and efficiency; however, they are also expensive, rigid or have poor mechanical properties, and they contain toxic or rare elements. Organic thermoelectrics have low cost, flexible mechanical properties, and facile and rapid formation; however, they have very low ZT values and efficiency compared with inorganic materials. Organic–inorganic composite thermoelectrics can benefit from both properties and are also extremely competitive for commercial applications. This review will focus on flexible organic–inorganic composite thermoelectrics and devices as well as their challenges.