High thermoelectric performance realized through manipulating layered phonon-electron decoupling

Abstract

Thermoelectric materials allow for direct conversion between heat and electricity, offering the potential for power generation. The average dimensionless figure of merit ZT ave determines device efficiency. N-type tin selenide crystals exhibit outstanding three-dimensional charge and two-dimensional phonon transport along the out-of-plane direction, contributing to a high maximum figure of merit Z max of ~3.6 × 10 −3 per kelvin but a moderate ZT ave of ~1.1. We found an attractive high Z max of ~4.1 × 10 −3 per kelvin at 748 kelvin and a ZT ave of ~1.7 at 300 to 773 kelvin in chlorine-doped and lead-alloyed tin selenide crystals by phonon-electron decoupling. The chlorine-induced low deformation potential improved the carrier mobility. The lead-induced mass and strain fluctuations reduced the lattice thermal conductivity. Phonon-electron decoupling plays a critical role to achieve high-performance thermoelectrics.

Mechanically Induced Highly Efficient Hydrogen Evolution from Water over Piezoelectric SnSe nanosheets

“…The positive slope of the C −2 curves obtained at three different frequencies (0.5, 1, and 1.5 kHz) indicates a n‐type semiconducting characteristics of the SnSe NSs (Figure S6, Supporting Information), which may originate from the chlorination induced during the synthesis process, in agreement with previous reports using similar solution‐phase synthesis methods [ 41 ] and our recent work. [ 42 ] According to the intercept of the Mott–Schottky plots, the flat band potential ( E fb vs NHE) can be determined to be around −0.35 eV ( E fb vs NHE = E Ag/AgCl + 0.197 eV) for SnSe NSs. As a result, the conduction band minimum (CBM) edge was estimated at −0.45 eV (the CBM is usually about 0.1 eV negative than the E fb for n‐type semiconductor), which is more negative than the potential of H + /H 2 (0 eV) and thus favorable for H 2 evolution reaction via water splitting.…”

Strategies to Improve the Thermoelectric Figure of Merit in Thermoelectric Functional Materials

“…At 600–800 K, SnSe has a continuous phase transition process from low-symmetry Pnma (L-Pnma) phase to high-symmetry Pnma (H-Pnma) phase, and then to high-temperature high-symmetry Cmcm phase. In addition to temperature, introducing stress into SnSe crystals by doping/solid solution can also adjust the symmetry of the crystal structure, thereby optimizing the thermoelectric properties of the material, as shown in Figure 4 ( Su et al, 2022 ).…”

“… 3D electron-2D phonon transport properties outside the n-type SnSe layer: Layered SnSe crystals use their layer structure to suppress (lattice vibration) phonon transport, but electrons different from phonons can tunnel through overlapping electron orbital transport ( Su et al, 2022 ). …”

“… The figure of merit of TE, thermoelectricity in recent years ( Ioffe et al, 1959 ; Cutler et al, 1964 ; Hicks and Dresselhaus, 1993 ; Horbach et al, 2001 ; Yang et al, 2001 ; Dashevsky et al, 2002 ; Kuznetsov et al, 2002 ; Hsu et al, 2004 ; Shutoh and Sakurada, 2005 ; Heremans et al, 2008 ; Poudel et al, 2008 ; Wang et al, 2008 ; Yang et al, 2008 ; Zhao et al, 2008 ; Xie et al, 2009 ; Bergum et al, 2011 ; Du et al, 2011 ; Levin et al, 2011 ; Pei et al, 2011 ; Li et al, 2012 ; Liu et al, 2012 ; Chen et al, 2013 ; Gelbstein et al, 2013 ; Sui et al, 2013 ; Yamini et al, 2013 ; Yan et al, 2013 ; Hu et al, 2014 ; Lee et al, 2014 ; Tan et al, 2014 ; Wu et al, 2014 ; Zhao et al, 2014a ; Zhao et al, 2014b ; Zhong et al, 2014 ; Kim et al, 2015 ; Kraemer et al, 2015 ; Tan et al, 2015a ; Tang et al, 2015 ; Liu et al, 2016 ; Tan et al, 2016a ; Liu et al, 2017 ; Roychowdhury et al, 2017 ; Zhang et al, 2017 ; Chang et al, 2018 ; Li et al, 2018 ; Zhou et al, 2018 ; Xiang et al, 2019 ; Chong et al, 2020 ; Feng et al, 2020 ; Qin et al, 2020 ; Yvenou et al, 2020 ; Selimefendigil et al, 2021 ; Su et al, 2022 ). …”

Two-dimensional multiferroic material of metallic p-doped SnSe

“…The group-IV monochalcogenides, such as SnSe, possess orthorhombic crystal structure 16,17 and have been predicted to be ferroelastic-ferroelectric multiferroics with spontaneous electric polarization and lattice strain 18,19 . Recently, the ferroelectricity has been experimentally validated in SnSe and SnS, respectively.…”