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Graphene quantum dots embedded in Bi2Te3 nanosheets to enhance thermoelectric performance Shuankui Li, Tianju Fan, Xuerui Liu, Fusheng Liu, Hong Meng, Yidong Liu, and Feng Pan ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b14274 • Publication Date (Web): 10 Jan 2017 Downloaded from http://pubs.acs.org on January 11, 2017
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ACS Applied Materials & Interfaces
Graphene Quantum Dots Embedded in Bi2Te3 Nanosheets to Enhance Thermoelectric Performance Shuankui Li, a† Tianju Fan, a† Xuerui Liu, a Fusheng Liu, b Hong Meng, a Yidong Liu, a* and Feng Pana* a
School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen,
518055, China. E-mail:
[email protected] (Prof. F. Pan) b
College of Materials Science and Engineering, Shenzhen University and Shenzhen Key
Laboratory of Special Functional Materials, Shenzhen, 518060, China. KEYWORDS: Thermoelectric materials, Graphene quantum dot, Hybrid nanostructure, Charged interface, Phonon scattering ABSTRACT: Novel Bi2Te3/Graphene quantum dot (Bi2Te3/GQDs) hybrid nanosheets with a unique structure that GQDs homogeneously embedded in the Bi2Te3 nanosheet matrix have been synthesized by a simple solution-based synthesis strategy. A significantly reduced thermal conductivity and enhanced powder factor are observed in the Bi2Te3/GQDs hybrid nanosheets, which is ascribed to the optimized thermoelectric transport properties of the Bi2Te3/GQDs interface. Furthermore, by varying the size of GQDs, the thermoelectric performance of Bi2Te3/GQDs hybrid nanostructures could be further enhanced, which could be attributed to the optimization of the density and dispersion manner of GQDs in the Bi2Te3 matrix. A maximum ZT of 0.55 is obtained at 425 K for the Bi2Te3/GQDs-20nm, which is higher than that of Bi2Te3
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without hybrid nanostrucure. This work provides the insights for the structural design and synthesis of Bi2Te3-based hybrid thermoelectric materials, which will be important for future development of broadly functional material system. 1. Introduction Bismuth telluride and their solid solutions are some of the most efficient thermoelectric materials near the room-temperature, but they are still not widely applied in useable thermoelectric devices because of the poor energy conversion efficiency.1-3 The conversion efficiency is characterized by the dimensionless figure-of-merit ZT= (S2σ/ҡ)T, where S, σ, ҡ, T are the Seebeck coefficient, electrical conductivity, total thermal conductivity, and absolute temperature, respectively. Obviously, an excellent thermoelectric material should have large power factor (S2σ) as well as low thermal conductivity, which is difficult to achieve in conventional material because of the interdependence of these three physical parameters.4-5 However, as the decreasing of the material dimensionality from conventional micro to nanometer, the new variable of length scale becomes available for controlling materials thermoelectric properties, which might allow new opportunities to optimize the three physical parameters independently. Extensive efforts have been made to controllable synthesis of Bi2Te3-based nanostructures. Various nanomaterials, such as nanowire,6 nanorod,7 nanoplates/nanosheets,8 nano-heterostructures, have been developed to improve their thermoelectric performances. 9-10 Moreover, constructed hybrid nanostructure with domain size comparable to or smaller than the carriers’ mean free path and/or coherence length is another promising way to realize the ballistic/coherent transport of heat and charge carriers. Unfortunately, limited works have been reported on the design and synthesis of Bi2Te3-based hybrid nanostructures with well-controlled components and interfaces to achieve simultaneously large power factor and low thermal conductivity.
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Graphene quantum dots (GQDs), a class of zero-dimensional carbon nanoparticles with typical dimensions of ca
