Atomically Thick Bismuth
Selenide Freestanding Single
Layers Achieving Enhanced Thermoelectric Energy Harvesting
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Abstract
Thermoelectric materials can realize significant energy
savings
by generating electricity from untapped waste heat. However, the coupling
of the thermoelectric parameters unfortunately limits their efficiency
and practical applications. Here, a single-layer-based (SLB) composite
fabricated from atomically thick single layers was proposed to optimize
the thermoelectric parameters fully. Freestanding five-atom-thick
Bi<sub>2</sub>Se<sub>3</sub> single layers were first synthesized
via a scalable interaction/exfoliation strategy. As revealed by X-ray
absorption fine structure spectroscopy and first-principles calculations,
surface distortion gives them excellent structural stability and a
much increased density of states, resulting in a 2-fold higher electrical
conductivity relative to the bulk material. Also, the surface disorder
and numerous interfaces in the Bi<sub>2</sub>Se<sub>3</sub> SLB composite
allow for effective phonon scattering and decreased thermal conductivity,
while the 2D electron gas and energy filtering effect increase the
Seebeck coefficient, resulting in an 8-fold higher figure of merit
(<i><i>ZT</i></i>) relative to the bulk material.
This work develops a facile strategy for synthesizing atomically thick
single layers and demonstrates their superior ability to optimize
the thermoelectric energy harvesting