The ability of substitution atoms to decrease thermal conductivity is usually ascribed to the enhanced phonon-impurity scattering by assuming the original phonon dispersion relations. In this study, we find that 10% SbGe alloying in GeTe modifies the phonon dispersions significantly, closes the acoustic–optical phonon band gap, increases the phonon–phonon scattering rates, and reduces the phonon group velocities. These changes, together with grain boundaries, nanoprecipitates, and planar vacancies, lead to a significant decrease in the lattice thermal conductivity. In addition, an extra 2–6% Zn alloying decreases the energy offset between valence band edges at L and Σ points in Ge1–x Sb x Te that is found to be induced by the Ge 4s2 lone pairs. Since Zn is free of s2 lone pair electrons, substituting Ge with Zn atoms can consequently diminish the Ge 4s2 lone-pair characters and reduce the energy offset, resulting in two energetically merged valence band maxima. The refined band structures render a power factor up to 40 μW cm–1 K–2 in Ge0.86Sb0.1Zn0.04Te. Ultimately, a superhigh zT of 2.2 is achieved. This study clarifies the impacts of high-concentration substitutional atoms on phonon band structure, phonon–phonon scattering rates, and the convergence of electron valence band edges, which could provide guidelines for developing high-performance thermoelectric materials.

High figure of merit is motivated by the development of novel thermoelectric theories. Here, we explore the Rashba effect to refine the band structure of Sndoped GeTe so that electronic transport is enhanced. The extra Sb alloying optimizes the carrier concentrations. Additionally, the co-existence of stacking faults with other multiscale nanostructures yields an ultra-low thermal conductivity. So, a figure of merit over 2.2 is achieved. The demonstrated strategy of Rashba spin splitting will enlighten the advance of next-generation thermoelectric materials.

Searching an effective method to enhance the thermoelectric properties of flexible organic films can significantly widen the application of flexible thermoelectric devices. Tuning the microstacking structure and oxidation level can effectively optimize the thermoelectric properties of poly(3,4-ethylenedioxithiophene):poly(styrenesulfonate) (PEDOT:PSS) organic films. Here, we adopt triple post-treatments with formamide (CH 3 NO), concentrated sulfuric acid (H 2 SO 4 ), and sodium borohydride in sequence to engineer flexible PEDOT:PSS thermoelectric films. A high power factor of 141 μWm −1 K −2 at 25 °C has been obtained for the PEDOT:PSS film. Such a high power factor stems from the high σ (1786 Scm −1 ) and S (28.1 μVK −1 ) after posttreatment with CH 3 NO, H 2 SO 4 , and NaBH 4 in order. The increased carrier mobility resulting from both the selective removal of excess insulating PSS within the films and the conformation transition after CH 3 NO and H 2 SO 4 treatments is responsible for the enhancement of σ, while the subsequent NaBH 4 treatment optimize the electrical properties (σ and S) by modulating the oxidation level. A homemade thermoelectric device has also been fabricated using the as-prepared flexible PEDOT:PSS films and had a high output power density of ∼1 μWcm −2 with human arm as a heating source. This study indicates that flexible thermoelectric devices based on cheap conducting polymers have great potential in wearable electronics.

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Enhanced thermoelectric performance by band convergence and superlattice precipitates combined with geometry optimization by computer-aided design produced a segmented thermoelectric device with a record-high conversion efficiency.