通过插层Cu实现SnSe_(2)的高效热电性能

Realizing high thermoelectric performance in SnSe_(2) via intercalating Cu

具有层状结构的SnSe展现出非常优异的热电性能.SnSe_(2)与其具有相似结构,但较低的电传输性能导致SnSe_(2)热电性能表现不佳,本征SnSe_(2)在773 K下最大ZT值仅约0.09.本文在Br掺杂提升SnSe_(2)载流子浓度的基础上,通过熔融法结合放电等离子烧结(SPS)技术合成了一系列成分为SnSe_(1.98)Br_(0.02–y)%Cu(y=0,0.50,0.75,1.00)的块体材料,研究了在具有层间范德瓦耳斯力结合的SnSe_(2)材料中引入额外的Cu对其电传输性能的协同优化作用:一方面,引入的Cu不仅能提供额外的电子,而且能稳定存在于范德瓦耳斯层间隙并形成插层结构,促进层间和层内的电荷传输,从而实现载流子浓度和迁移率的协同优化;另一方面,Cu的动态掺杂特性,使得高温下载流子浓度的增加弥补了因散射作用导致的迁移率的降低,促使样品在高温下仍然保持高电传输特性.研究结果表明,在300 K下,SnSe_(2)沿平行和垂直于SPS烧结方向(//P,⊥P)的功率因子(PF)分别从本征的约0.65和0.98μW·cm^(–1)·K^(–2)提高到SnSe_(1.98)Br_(0.02)–0.75%Cu的约10和19μW·cm^(–1)·K^(–2).最终,在773 K下,沿⊥P方向的最大ZT值达到约0.8.此研究表明SnSe_(2)是一种很具发展潜力的热电材料.

SnSe,a layered material with intrinsic low thermal conductivity,is reported to have excellent thermoelectric properties.SnSe_(2)has a similar structure to SnSe,but the SnSe_(2)has a low electrical transport,resulting in a poor thermoelectric performance,and the intrinsic SnSe_(2)has a maximum ZT value of only~0.09 at 773 K.In this work,SnSe_(1.98)Br_(0.02-y)%Cu(y=0,0.50,0.75,1.0)bulk materials are synthesized by the melting method combined with spark plasma sintering(SPS)based on the carrier concentration improved through Br doping.In the SnSe_(2)materials with van der Waals chemical bonding between layers,the synergistic effects of intercalating Cu on the thermoelectric properties are investigated.On the one hand,the extra Cu not only provides additional electrons but also can be embedded stably in the van der Waals gap and form an intercalated structure,which is beneficial to the charge transfer in or out of the layers,and thus synergistically improving the carrier concentration and carrier mobility.On the other hand,owing to the dynamic Cu doping,the increase of carrier concentration compensates for the decrease of carrier mobility caused by carrier-carrier scattering,which maintains the high electrical transport properties at high temperature.The present results show that at room temperature,the power factors along the parallel and perpendicular to the SPS(//P and⊥P)sintering directions increase from~0.65 and~0.98μW·cm^(–1)·K^(–2) for intrinsic SnSe_(2)to~10 and~19μW·cm^(–1)·K^(–2) for SnSe_(1.98) B_(r0.02)-0.75%Cu samples,respectively.Finally,at 773 K,the maximum ZT value of~0.8 is achieved along the⊥P direction.This study proves that the SnSe_(2)greatly promises to become an excellent thermoelectric material.