High Thermoelectric Performance through Crystal Symmetry Enhancement in Triply Doped Diamondoid Compound Cu2SnSe3. Issue 42 (9th October 2021)

• Record Type: Journal Article
• Authors: Hu, Lei; Luo, Yubo; Fang, Yue‐Wen; Qin, Feiyu; Cao, Xun; Xie, Hongyao; Liu, Jiawei; Dong, Jinfeng; Sanson, Andrea; Giarola, Marco; Tan, Xianyi; Zheng, Yun; Suwardi, Ady; Huang, Yizhong; Hippalgaonkar, Kedar; He, Jiaqing; Zhang, Wenqing; Xu, Jianwei; Yan, Qingyu; Kanatzidis, Mercouri G.
• Is Part Of: Advanced energy materials. Volume 11:Issue 42(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-10-09
• Subjects: crystal symmetry -- diamondoid structure -- nanoscale defects -- thermoelectrics; Energy harvesting -- Materials -- Periodicals; Energy conversion -- Materials -- Periodicals; Energy storage -- Materials -- Periodicals; Photovoltaics -- Periodicals; Fuel cells -- Periodicals; Thermoelectric materials -- Periodicals; 621.31
• DOI: 10.1002/aenm.202100661
• Languages: English
• ISSNs: 1614-6832

Abstract

Abstract: The presence of high crystallographic symmetry and nanoscale defects are favorable for thermoelectrics. With proper electronic structures, a highly symmetric crystal tends to possess multiple carrier channels and promote electrical conductivity without sacrificing Seebeck coefficient. In addition, nanoscale defects can effectively scatter acoustic phonons to suppress thermal conductivity. Here, it is reported that the triple doping of Cu2 SnSe3 leads to a high ZT value of 1.6 at 823 K for Cu1.85 Ag0.15 (Sn0.88 Ga0.1 Na0.02 )Se3, and a decent average ZT ( ZT ave ) value of 0.7 is also achieved for Cu1.85 Ag0.15 (Sn0.93 Mg0.06 Na0.01 )Se3 from 475 to 823 K. This study reveals: 1) Ag doping on Cu sites generates numerous point defects and greatly decreases lattice thermal conductivity. 2) Doping Mg or Ga converts the monoclinic Cu2 SnSe3 into a cubic structure. This symmetry enhancing leads to an increase in the effective mass from 0.8 m e to 2.6 m e ( m e, free electron mass) and the power factor from 4.3 µW cm −1 K −2 for Cu2 SnSe3 to 11.6 µW cm −1 K −2 . 3) Na doping creates dense dislocation arrays and nanoprecipitates, which strengthens the phonon scattering. 4) Pair distribution function analysis shows localized symmetry breakdown in the cubic Cu1.85 Ag0.15 (Sn0.88 Ga0.1 Na0.02 )Se3 . This work provides a standpoint to design promising thermoelectric materials by synergistically manipulating crystal symmetry and nanoscale defects. Abstract : The highest ZT value of 1.6 at 823 K is achieved in the diamondoid compound Cu2 SnSe3 by a triple doping strategy. Crystal symmetry enhanced from monoclinic to cubic leads to band convergence, favorable for electrical properties. The existence of nanoscale defects effectively decreases lattice thermal conductivity. The joint effect produces the highest ZT value in thermoelectric materials with diamondoid structures.