Enhanced Thermoelectric Performance in Lead-Free Inorganic CsSn1–xGexI3Perovskite Semiconductors

Halide perovskite semiconductors exhibit ultralow thermal conductivities, making them potentially suitable for thermoelectric applications. Nevertheless, the thermoelectric properties of the prototypical halide perovskite of CH3NH3PbI3have been limited with a very low dimensionless figure of merit (ZT) and a narrow operating temperature window, which are attributed to its poor electronic conductivity and unstable hybrid organic–inorganic composition, respectively. Here, we report the bulk synthesis of a stable, all-inorganic halide perovskite of CsSn0.8Ge0.2I3as a new thermoelectric material, which shows a 10 order of magnitude enhancement in ZT compared with that of CH3NH3PbI3and an operating temperature as high as 473 K. Importantly, this CsSn0.8Ge0.2I3perovskite is also Pb-free in the composition, attesting its high potential as an environmentally friendly candidate material for future thermoelectrics.