Thermoelectric Performance of CuInTe₂ from First Principles Using Hybrid-DFT and Lattice Dynamics

Fossil fuels provide 80% of the world’s energy¹ and of that energy, an estimated 80% is wasted in the form of heat.² This has motivated world leaders to invest in alternative forms of energy generation.³ One such alternative to be explored is the use of thermoelectric materials (TE).<br/>Thermoelectric materials can convert heat into electricity through the Seebeck effect allowing them to increase the overall efficiency of existing processes, as well as serve as a clean source of electricity. Materials in use today are composed of toxic elements like lead or are plagued by low efficiencies. To measure thermoelectric efficiency, we use the figure of merit, ZT. For comparison, the average ZT of a well-known TE that has been used in many NASA space missions, PbTe is 1.4.⁴<br/>In this work, we explore a chalcopyrite semiconductor, CuInTe₂ (CIT) with an experimental ZT of 1.18 at 850 K⁵ which has been predicted to increase up to 1.72 (10¹⁸ carriers cm^-3).⁶ The hybrid-DFT functional (HSE06) with spin-orbit coupling (SOC) is used to accurately predict the band structure and the AMSET code⁷ is used to calculate the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and mobility. We use the supercell approach employed by Phono3py⁸ to calculate third-order phonon-phonon interactions and determine the lattice thermal conductivity. These results allow us to fully calculate the ZT of CIT from first principles where previous theoretical studies have used a semi-empirical approach.⁶<br/>A fundamental understanding of the dopability is key to yielding a proper prediction of the thermoelectric performance, therefore, a study of the full defect chemistry using hybrid-DFT will give insights into realistic doping concentrations by calculating the self-consistent fermi level. We will also assess the effect of different dopants on ZT. This can help guide experimental studies by screening a range of dopants that haven’t been studied before in this system such as Sb.⁹<br/><br/>1 Fossil Fuels | EESI, https://www.eesi.org/topics/fossil-fuels/description, (accessed 26 April 2022).<br/>2 Q. Bian, <i>Environ. Syst. Res.</i>, 2020, <b>9</b>, 8.<br/>3 P. A. Finn, C. Asker, K. Wan, E. Bilotti, O. Fenwick and C. B. Nielsen, <i>Front. Electron. Mater.</i><br/>4 X. Hao, X. Chen, X. Zhou, L. Zhang, J. Tao, C. Wang, T. Wu and W. Dai, <i>Front. Energy Res.</i><br/>5 R. Liu, L. Xi, H. Liu, X. Shi, W. Zhang and L. Chen, <i>Chem. Commun.</i>, 2012, <b>48</b>, 3818–3820.<br/>6 J. Wei, H. J. Liu, L. Cheng, J. Zhang, J. H. Liang, P. H. Jiang, D. D. Fan and J. Shi, <i>AIP Adv.</i>, 2015, <b>5</b>, 107230.<br/>7 A. M. Ganose, J. Park, A. Faghaninia, R. Woods-Robinson, K. A. Persson and A. Jain, <i>Nat. Commun.</i>, 2021, <b>12</b>, 2222.<br/>8 A. Togo, L. Chaput and I. Tanaka, <i>Phys. Rev. B</i>, 2015, <b>91</b>, 094306.<br/>9 S. Hachmioune et al. (in submission)