Materials informatics platform with three dimensional structures, workflow and thermoelectric applications

High throughput screening of semiconductors with low lattice thermal transport induced by long-range interactions

Semiconductors with long-range interactions (LRI) due to resonant bonding exhibit delocalized electronic states and low lattice thermal conductivity, contributing to the efficiency of heat-to-electricity conversion. Here, we build a descriptor for high-throughput screening of LRI materials from the second-order interaction force constants. We identify 75 semiconducting candidates from the binary compounds in the MatHub-3d database that contain LRI. By analyzing the bonding properties of LRI atoms, we classify LRI in materials into two categories: type I and type II. In the structural unit of type I LRI, the atoms have strong bond connections, while a weak bond exists between the two groups in the structural unit of type II LRI. We have identified atypical type I LRI formed by Sb-Sb and Mg-Mg pairs in the emerging thermoelectric material Mg3Sb2, resulting in the softening of TA1 phonons and large anharmonicity. For type II LRI, the LRI of Ge-Ge and Se-Se pairs in R3m-GeSe can cross different layers. Moreover, we observe a combination of type II LRI and rattling effect in BaSe2 to restrict thermal transport. This work is of great significance for understanding the relationship between LRI and thermal transport properties, and for designing new LRI-induced low lattice thermal conductivity materials.

High throughput calculations for a dataset of bilayer materials

Bilayer materials made of 2D monolayers are emerging as new systems creating diverse opportunities for basic research and applications in optoelectronics, thermoelectrics, and topological science among others. Herein, we present a computational bilayer materials dataset containing 760 structures with their structural, electronic, and transport properties. Different stacking patterns of each bilayer have been framed by analyzing their monolayer symmetries. Density functional theory calculations including van der Waals interactions are carried out for each stacking pattern to evaluate the corresponding ground states, which are correctly identified for experimentally synthesized transition metal dichalcogenides, graphene, boron nitride, and silicene. Binding energies and interlayer charge transfer are evaluated to analyze the interlayer coupling strength. Our dataset can be used for materials screening and data-assisted modeling for desired thermoelectric or optoelectronic applications.

Functional-Unit-Based Material Design: Ultralow Thermal Conductivity in Thermoelectrics with Linear Triatomic Resonant Bonds

We demonstrate the use of functional-unit-based material design for thermoelectrics. This is an efficient approach for identifying high-performance thermoelectric materials, based on the use of combinations of functional fragments relevant to desired properties. Here, we reveal that linear triatomic resonant bonds (LTRBs) found in some Zintl compounds provide strong anisotropy both structurally and electronically, along with strong anharmonic phonon scattering. An LTRB is thus introduced as a functional unit, and compounds are then screened as potential thermoelectric materials. We identify 17 semiconducting candidates from the MatHub-3d database that contain LTRBs. Detailed transport calculations demonstrate that the LTRB-containing compounds not only have considerably lower lattice thermal conductivities than other compounds with similar average atomic masses, but also exhibit remarkable band anisotropy near the valence band maximums due to the LTRB. K₅CuSb₂ is adopted as an example to elucidate the fundamental correlation between the LTRB and thermoelectric properties. The [Sb-Cu-Sb]^5- resonant structures demonstrate the delocalized Sb-Sb interaction within each LTRB, resulting in the softening of TA phonons and leading to large anharmonicity. The low lattice thermal conductivity (0.39 W/m·K at 300 K) combined with the band anisotropy results in a high thermoelectric figure of merit (ZT) for K₅CuSb₂ of 1.3 at 800 K. This work is a case study of the functional-unit-based material design for the development of novel thermoelectric materials.

High-Throughput Screening for Thermoelectric Semiconductors with Desired Conduction Types by Energy Positions of Band Edges

The conduction type of semiconductors is vitally important in many fields (e.g., photovoltaics, transistors, and thermoelectrics), but so far, there is no effective and simple indicator to quickly judge or predict the conduction type of various semiconductors. In this work, based on the relationship between the formation energy of charged defect and the Fermi level, we propose a simple and low-cost strategy for high-throughput screening the potential n-type or p-type semiconductors from the material database by using energy positions of band edges as indicators. As a case study, we validate this strategy in searching potential n-type thermoelectric materials from copper (Cu)-containing metal chalcogenides. A new promising thermoelectric material, CuIn₅Se₈, with potential intrinsic n-type conduction, is successfully screened from 407 Cu-containing metal chalcogenides and validated in the subsequent experiments. Upon doping iodine in CuIn₅Se₈, a peak thermoelectric figure of merit zT of 0.84 is obtained at 850 K. Beyond thermoelectrics, the strategy proposed in this study also sheds light on the new material development with desired conduction types in photovoltaics, transistors, and other fields.