posted on 2020-03-11, 13:49authored byBingchao Qin, Yang Zhang, Dongyang Wang, Qian Zhao, Bingchuan Gu, Haijun Wu, Hongjun Zhang, Bangjiao Ye, Stephen J. Pennycook, Li-Dong Zhao
Crystalline
SnSe has been revealed as an efficient thermoelectric
candidate with outstanding performance. Herein, record-high thermoelectric
performance is achieved among SnSe crystals via simply introducing
a small amount of SnSe2 as a kind of extrinsic defect dopant.
This excellent performance mainly arises from the largely enhanced
power factor by increasing the carrier concentration high as 6.55
× 1019 cm–3, which was surprisingly
promoted by introducing extrinsic SnSe2 even though pristine
SnSe2 is an n-type conductor. The optimized carrier concentration
promotes a deeper Fermi level and activates more valence bands, leading
to an extraordinary room-temperature power factor ∼54 μW
cm–1 K–2 through enlarging the
band effective mass and Seebeck coefficient. As a result, on the basis
of simultaneously depressed thermal conductivity induced from both
Sn vacancies and SnSe2 microdomains, maximum ZT values ∼0.9–2.2 and excellent average ZT > 1.7 among the working temperature range are achieved in Na
doped
SnSe crystals with 2% extrinsic SnSe2. Our investigation
illustrates new approaches on improving thermoelectric performance
through introducing defect dopants, which might be well-implemented
in other thermoelectric systems.