Lawrence Berkeley National Laboratory
Solvent-free synthesis of organometallic halides CH3NH3PbI3 and (CH3NH3)3Bi2I9 and their thermoelectric transport properties
- Author(s): Long, Xiang
- Pan, Zhenyu
- Zhang, Zhuolei
- Urban, Jeffrey J
- Wang, Heng
- et al.
Published Web Locationhttp://doi.org/10.1063/1.5113535
© 2019 Author(s). Organometallic halides are great candidates for optoelectronics. As an important family of semiconductors, understanding their thermoelectric transport properties is also important. This has been a challenging task as many of such compounds are highly intrinsic. In this work, we synthesized two halides, CH3NH3PbI3 and (CH3NH3)3Bi2I9, using a solvent-free method. We found an extraordinarily high Seebeck coefficient of +2600 ± 200 μV/K in (CH3NH3)3Bi2I9. For CH3NH3PbI3, our synthesis method led to a negative Seebeck coefficient of -1350 ± 50 μV/K, in contrast to positive values observed in solvent synthesized samples. We also found the thermal conductivity of CH3NH3PbI3 to be 0.38 W/m K, largely independent of temperature from 300 K to 450 K, despite a tetragonal-to-cubic phase transition. (CH3NH3)3Bi2I9 has an even lower thermal conductivity of 0.21 W/m K (also temperature independent) which is due to its soft phonon dispersion and weak bonds.