Halide Perovskites as Thermoelectric Materials

Halide perovskites are well known as promising candidates for photovoltaics and light-emitting diodes. Additionally, promising thermoelectric performance has been reported for a small number a halide perovskites, with this class of materials offering ultralow thermal conductivity, good Seebeck coefficients and potential advantages in processing and sustainability. However, there is not yet a good understanding of how thermoelectric performance of halide perovskites can be optimised. This talk will cover the origins of ultralow thermal conductivity and quanitfy both the Lorenz number and the thermal boundary resistance [3] in polycrystalline films. Extrinsic doping and self-doping will be discussed as methods to optimise the thermoelectric figure of merit zT, with values of zT reaching 0.14 in CsSnI₃ [2] The case of self-doping by Sn-oxidation in CsSnI₃ will be examined in detail and strategies to improve performance and control the rate of oxidation by modification of deposition procedures, or by using mixed halide and mixed metal stoichiometries will be presented. Thin-film vapour deposition, single crystal growth [1] and solid-state synthesis of pellets will be discussed, along with doping techniques to improve stability and conductivity.<br/><br/>[1] Tang, W; Zhang, J; Ratnasingham, SR; et al<b>., <b>Substitutional doping of hybrid organic-inorganic perovskite crystals for thermoelectrics</b></b>, <i>J. Mater. Chem. A 2020,</i> <b>8</b>, 13594 – 13599.<br/>[2] Liu, T; Zhao, X; Li, J; Liu, Z; Liscio, F; Milita, S; Schroeder, BC; Fenwick, O <b>Enhanced control of self-doping in halide perovskites for improved thermoelectric performance</b>, <i>Nature Communications</i>, 2019, <b>10</b>(1):5750.<br/>[3] Liu, T; Yue, SY; Ratnasingham, SR; Degousée, T; Varsani, PR; Briscoe, J; McLachlan, MA; Hu, M; Fenwick, O <b>Unusual thermal boundary resistance in halide perovskites: A way to tune ultralow thermal conductivity for thermoelectrics, </b><i>ACS Applied Materials and Interfaces</i>, 2019, <b>11</b> (50), 47507–47515.