Investigating The Potential of III-V Type-I Clathrates as Thermoelectrics: A Computational Perspective

The significant impact of III-V semiconductors on the electronic materials landscape is indisputable, demonstrated by their widespread use in high-profile applications such as integrated circuits, LEDs, and advanced photovoltaics. Innovations in materials discovery have ushered in the synthesis of type-I clathrate structures with a III-V host framework, exhibiting remarkable p-type mobilities [1]. Clathrate structures, consisting of nanometre-sized polyhedral cages encapsulating guest atoms or molecules, have stirred interest as prospective battery electrodes, photovoltaics, but most relevantly as thermoelectrics [2]. The highly electronically conductive framework coupled with weakly bound "rattler" guest atoms leads to fast electron transport and poor thermal transport, thus fulfilling the 'phonon-glass electron crystal' concept and paving the way for exceptional thermoelectric materials. Despite this notable potential, there exist significant discrepancies previous between theoretical predictions and experimental studies of these materials' properties [1], which our research aims to resolve. In our study, we integrate atomistic simulations with data-driven methodologies to screen and characterize both existing and novel clathrates within the III-V compositional space. Employing the SMACT materials informatics tool [3], we efficiently navigate the vast compositional search space of III-V clathrates using economical heuristic tools, refining the search by evaluating the stability of the proposed clathrates using density functional theory. We further utilized spin-orbit coupling corrected hybrid density functional theory to provide a comprehensive first-principles characterization of these materials' electronic structures. Finding that this alone does not reconcile the experimental-theoretical disparities, we explore the strong influences of disorder and off-stoichiometry on their target properties. Our findings present deeper insights into this exciting class of materials, and offers a range of potential new applications.<br/><br/>1. Owens-Baird et al., Journal of the American Chemical Society, 2020, 142, 4, 2031–2041<br/>2. Krishna, L., & Koh, C., Inorganic and methane clathrates: Versatility of guest–host compounds for energy harvesting. MRS Energy & Sustainability, 2, E8, 2015.<br/>3. Davies et al., SMACT: Semiconducting Materials by Analogy and Chemical Theory. Journal of Open Source Software, 2019, 4(38), 1361