Advances in Versatile GeTe Thermoelectrics from Materials to Devices

Abstract

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202208272. = − + ZT S S T (3) in the above equations, T cold and T hot are cold-and hot-end temperatures. ΔT = T hot − T cold , T = (T hot + T cold )/2. S i is the Seebeck coefficient, σ i is the electrical conductivity, and κ i is the thermal conductivity with the subscript i representing n-or p-type materials. Since such a Z T is defined by assuming the temperature-independent S i , σ i , and κ i under the temperature Driven by the intensive efforts in the development of high-performance GeTe thermoelectrics for mass-market application in power generation and refrigeration, GeTe-based materials display a high figure of merit of >2.0 and an energy conversion efficiency beyond 10%. However, a comprehensive review on GeTe, from fundamentals to devices, is still needed. In this regard, the latest progress on the state-of-the-art GeTe is timely reviewed. The phase transition, intrinsic high carrier concentration, and multiple band edges of GeTe are fundamentally analyzed from the perspectives of the native atomic orbital, chemical bonding, and lattice defects. Then, the fabrication methods are summarized with a focus on large-scale production. Afterward, the strategies for enhancing electronic transports of GeTe by energy filtering effect, resonance doping, band convergence, and Rashba band splitting, and the methods for strengthening phonon scatterings via nanoprecipitates, planar vacancies, and superlattices, are comprehensively reviewed. Besides, the device assembly and performance are highlighted. In the end, future research directions are concluded and proposed, which enlighten the development of broader thermoelectric materials.

Ce‐filled Ni1.5Co2.5Sb12 Skutterudite Thin Films with Record‐High Figure of Merit And Device Performance

“…[1] The science such as machine learning are employed to guide the finding of new thermoelectric material systems with potentially high ZTs, as well as the improvement of current thermoelectric materials. [10,11] Till now, many bulk thermoelectric materials have exhibited high experimental ZTs of >2 or even ≈3, which are promising for practical applications, such as GeTe, [12] SnSe, [9] Cu 2 Se/Te, [13] and PbTe. [14] However, these materials are difficult to keep their high thermoelectric performance when acting as thin films.…”

Effects of Si Substrates with Variable Initial Orientations on the Growth and Thermoelectric Properties of Bi-Sb-Te Thin Films

“…Recently, some new material systems, including Ag 2 Se, Cu 2 Se, Mg 3 Sb 2 et al showed outstanding properties and thus performance [ 7 , 8 , 9 , 10 ]. For example, Ding et al reported an n-type Ag 2 Se film on flexible nylon membrane with an ultrahigh power factor ~9.9 μWm −1 K −2 at 300 K with excellent flexibility [ 11 ].…”

Vacancy Suppression Induced Synergetic Optimization of Thermoelectric Performance in Sb-Doped GeTe Evidenced by Positron Annihilation Spectroscopy

“…In recent years, GeTe-based materials have attracted extensive attention for their promising TE applications. − It is well known that the pristine GeTe is a typical p-type degenerate semiconductor with a huge number of intrinsic Ge vacancies, leading to the abundant hole carrier concentration (∼10 21 cm –3 at 300 K) . The excess carrier concentration is detrimental to the TE performance and, thus, provides a lot of room for performance optimization .…”