Disorder-induced Anderson-like localization for bidimensional thermoelectrics optimization

• Published in: Matter Vol. 4; no. 9; pp. 2970 - 2984
• Main Authors: Agne, Matthias T., Lange, Felix R.L., Male, James P., Siegert, K. Simon, Volker, Hanno, Poltorak, Christian, Poitz, Annika, Siegrist, Theo, Maier, Stefan, Snyder, G. Jeffrey, Wuttig, Matthias
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.09.2021
• Subjects: charge transport; disorder; electronic conductivity; GST; localization; metavalent bonding; phase change materials; Seebeck coefficient; thermoelectrics; localization; Seebeck coefficient; disorder; MAP5: Improvement; thermoelectrics; metavalent bonding; phase change materials; GST; electronic conductivity; charge transport
• ISSN: 2590-2385; 2590-2385
• DOI: 10.1016/j.matt.2021.07.017

Thermoelectric materials could play an important role in global sustainable energy. However, improving thermoelectric efficiency has proved difficult, largely due to the complex interdependence of electronic properties of solids. Early work by Ioffe has developed into the standard thermoelectric optimization paradigm of tuning the electronic carrier concentration in semiconductors. Although the localization theory of electrons by Anderson and Mott has developed in parallel, its potential for thermoelectrics optimization has not been explored. Here, we show that structural-disorder-induced electron localization also provides an effective optimization strategy for thermoelectric materials. By using a transport model that includes the relevant physics of localization, it is shown that the maximum thermoelectric figure of merit can be increased ∼20% by tuning both carrier concentration and disorder. The benefit of slight disorder is confirmed in two model Ge-Sb-Te material systems. Particularly for highly degenerate semiconductors, this bidimensional optimization strategy provides a new methodology to attain high thermoelectric performance. [Display omitted] •Charge transport model for order-disorder transitions•Characterization of Anderson-like localization effects•Disorder optimization of thermoelectric materials A certain level of disorder is inherent to every solid, since it contributes to entropy and minimizes the Gibbs free energy of a system in thermodynamic equilibrium and can be a defining quality of metastable materials like glasses. Controlling and manipulating disorder provides scientists with excellent and widespread opportunities to optimize material properties (e.g., the electronic conductivity). Such endeavors (e.g., optimizing thermoelectrics, photovoltaics, batteries, and [micro]electronics) require a profound understanding of charge transport in solids. This work provides a transferable and experimentally verified model that adds to our understanding of charge transport in disordered solids. By including the relevant physics of Anderson-like electron localization with current state-of-the-art methods of thermoelectric material optimization, we demonstrate a new avenue of charge transport engineering in solids. Decades of thermoelectric research has focused on the optimization of charge carrier concentration to maximize the thermoelectric efficiency. However, analytical considerations of electron localization show that some degree of structural disorder can be necessary to reach the true optimum of thermoelectric efficiency. This is experimentally demonstrated in an exemplary Ge-Sb-Te material system. Furthermore, a quantitative transport model is developed that gives insights for disorder-controlled electronic transport beyond thermoelectrics, including phase-change materials and microelectronics.