Blocking Ion Migration Stabilizes the High Thermoelectric Performance in Cu2Se Composites. Issue 40 (2nd September 2020)

• Record Type: Journal Article
• Authors: 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
• Is Part Of: Advanced materials. Volume 32:Issue 40(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-09-02
• Subjects: Cu 2Se -- mixed ionic–electronic conductors -- Schottky junction -- stable thermoelectric materials -- thermoelectric properties; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.202003730
• Languages: English
• ISSNs: 0935-9648

Abstract

Abstract: 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 Cu2 Se is stabilized through regulating the behaviors of Cu + ions and electrons in a Schottky heterojunction between the Cu2 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 Cu2 Se, obstructing the reduction reaction of Cu + into Cu metal at the interface and hence stabilizes the β‐Cu2 Se phase. Furthermore, incorporation of BiCuSeO in Cu2 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 Cu2 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. Abstract : The space‐charge region between Cu2 Se host matrix and in‐situ‐formed BiCuSeO under a direct current causes drastic suppression of the Cu + ion migration in such composites and obstructs the reduction reaction of Cu + into Cu metal. This, together with the effective regulation of carrier concentration as well as enhanced interfacial phonon scattering, greatly stabilizes the improved thermoelectric performance.