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Blocking Ion Migration Stabilizes the High Thermoelectric Performance in Cu 2 Se Composites
Author(s) -
Yang Dongwang,
Su Xianli,
Li Jun,
Bai Hui,
Wang Shanyu,
Li Zhi,
Tang Hao,
Tang Kechen,
Luo Tingting,
Yan Yonggao,
Wu Jinsong,
Yang Jihui,
Zhang Qingjie,
Uher Ctirad,
Kanatzidis Mercouri G.,
Tang Xinfeng
Publication year - 2020
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.202003730
Subject(s) - materials science , ionic bonding , thermoelectric effect , ion , schottky barrier , composite material , thermoelectric materials , space charge , condensed matter physics , electron , optoelectronics , thermal conductivity , physics , diode , quantum mechanics , thermodynamics
The applications of mixed ionic–electronic conductors are limited due to phase instability under a high direct current and large temperature difference. Here, it is shown that Cu 2 Se is stabilized through regulating the behaviors of Cu + ions and electrons in a Schottky heterojunction between the Cu 2 Se host matrix and in‐situ‐formed BiCuSeO nanoparticles. The accumulation of Cu + ions via an ionic capacitive effect at the Schottky junction under the direct current modifies the space‐charge distribution in the electric double layer, which blocks the long‐range migration of Cu + and produces a drastic reduction of Cu + ion migration by nearly two orders of magnitude. Moreover, this heterojunction impedes electrons transferring from BiCuSeO to Cu 2 Se, obstructing the reduction reaction of Cu + into Cu metal at the interface and hence stabilizes the β‐Cu 2 Se phase. Furthermore, incorporation of BiCuSeO in Cu 2 Se optimizes the carrier concentration and intensifies phonon scattering, contributing to the peak figure of merit ZT value of ≈ 2.7 at 973 K and high average ZT value of ≈ 1.5 between 400 and 973 K for the Cu 2 Se/BiCuSeO composites. This discovery provides a new avenue for stabilizing mixed ionic–electronic conduction thermoelectrics, and gives fresh insights into controlling ion migration in these ionic‐transport‐dominated materials.