Inorganic halogen perovskite CsBI₃ (B = Pb, Sn, and Ge) thermoelectric material

In recent years, there has been a growing interest in thermoelectric conversion materials that convert the various waste heat into electric energy, while actively utilizing renewable energy including solar, geothermal and wind energy. Unlike traditional thermoelectric conversion materials, halogen perovskite materials are regarded as promising candidates due to their abundant resources, very low fabrication cost and excellent thermoelectric properties.

We have applied the first-principles material design method based on density functional theory to evaluate the thermoelectric conversion performance of inorganic halogen perovskite CsBI₃ (B = Ge, Sn, Pb) by studying the lattice dynamics and transport properties.

First, crystal structure optimization was carried out using PBEsol exchange-correlation functionals for inorganic halogen perovskite CsBI₃ (B = Ge, Sn, Pb) to obtain lattice parameters that are in good agreement with previous experimental studies, and then lattice dynamics and transport properties were studied using the optimized crystal structures.

Next, we conducted a first-principles study of the electronic structure and electron transport properties of inorganic halogen perovskite CsBI₃ (B = Ge, Sn, Pb) and evaluated the thermoelectric conversion performance of this material.

Figure. Figure of merit at T = 700 K as a function of carrier concentration in cubic CsBI₃ (B = Pb, Sn, and Ge)

Figure of merit at T = 700 K as a function of carrier concentration in cubic CsBI₃ is shown in the Figure. As CsGeI₃ has a low thermal conductivity and a high figure of merit ZT, it is more favorable for the thermo-electric conversion with ZT of about 1.2 upon n-type doping at 700K compared to GeTe with ZT of 0.9. The results show that inorganic halogen perovskite CsBI₃ (B = Ge, Sn, Pb) has very low lattice thermal conductivity and high figure of merit, which makes it possible to apply it to the fabrication of low-cost and high-efficiency thermo-electric conversion devices.

This result has been published in "The Journal of the Physical Chemistry C" under the title of "High Thermoelectric Performance in the Cubic Inorganic Cesium Iodide Perovskites CsBI₃(B=Pb, Sn, and Ge) from First-Principles" (https://doi.org/10.1021/acs.jpcc.0c09929).