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Rahul Singh, Ranjith Kottokkaran, Vikram L Dalal, Ganesh Balasubramanian
Organic/inorganic lead and tin halide perovskites (CH3NH3PbI3 and CH3NH3SnI3) have been promising for photovoltaics because of their high charge carrier mobility, and large absorption coefficient and diffusion length. Both these perovskites also have a notable Seebeck coefficient, depending on the doping level, indicating their potential as thermoelectrics. We create superlattices of these hybrid organic-inorganic halide perovskites and investigate electronic transport through them using first principles computations and experiments...
May 23, 2017: Nanoscale
Yihan Wang, Jie Yang, Lingyu Wang, Kai Du, Qiang Yin, QinJian Yin
Polypyrrole/Graphene/Polyaniline (PPy/GNs/PANi) ternary nanocomposite with high thermoelectric power factor has been successfully prepared through the combination of in situ polymerization and solution process. FTIR, Raman spectra, XRD and SEM analyses show the strong π-π interactions existed among PPy, GNs and PANi, leading to the formation of more ordered regions in the composite. Both the in situ polymerization and solution process can enhance the dispersion homogeneity of graphene in the polymer matrix, bringing about increased nano-interfaces in the PPy/GNs/PANi composite...
May 22, 2017: ACS Applied Materials & Interfaces
Kelly W Mauser, Seyoon Kim, Slobodan Mitrovic, Dagny Fleischman, Ragip Pala, K C Schwab, Harry A Atwater
Photodetectors are typically based either on photocurrent generation from electron-hole pairs in semiconductor structures or on bolometry for wavelengths that are below bandgap absorption. In both cases, resonant plasmonic and nanophotonic structures have been successfully used to enhance performance. Here, we show subwavelength thermoelectric nanostructures designed for resonant spectrally selective absorption, which creates large localized temperature gradients even with unfocused, spatially uniform illumination to generate a thermoelectric voltage...
May 22, 2017: Nature Nanotechnology
Guangzhao Qin, Zhenzhen Qin, Sheng-Ying Yue, Qing-Bo Yan, Ming Hu
The manipulation of thermal transport is in increasing demand as heat transfer plays a critical role in a wide range of practical applications, such as efficient heat dissipation in nanoelectronics and heat conduction hindering in solid-state thermoelectrics. It is well established that the thermal transport in semiconductors and insulators (phonons) can be effectively modulated by structure engineering or materials processing. However, almost all the existing approaches involve altering the original atomic structure of materials, which would be hindered due to either irreversible structure change or limited tunability of thermal conductivity...
May 17, 2017: Nanoscale
Tongzhou Wang, Congcong Liu, Fengxing Jiang, Zhaofen Xu, Xiaodong Wang, Xia Li, Changcun Li, Jingkun Xu, Xiaowei Yang
Graphene-based two-dimensional (2D) heterostructures have ignited intensive interest in recent years because of their excellent physical performance. However, the most common method to prepare them uses chemical vapor deposition, which has the drawback of a complex process unsuitable for large-scale production. In this respect, reduced graphene oxide and transitional metal dichalcogenides (rGO-TMDs) composite thin-films were fabricated by a simple solution-processing method and their thermoelectric performance was investigated systematically...
May 17, 2017: Physical Chemistry Chemical Physics: PCCP
Changcun Li, Fangfang Kong, Congcong Liu, Huixuan Liu, Yongjing Hu, Tongzhou Wang, Jingkun Xu, Fengxing Jiang
The wet-chemical approach is of great significance for the synthesis of two-dimensional (2D) bismuth telluride nanoplatelets as a potential thermoelectric (TE) material. Herein, we proposed a simple and effective solution method with the assistance of aniline for the fabrication of bismuth telluride nanoplatelets at a low temperature of 100 °C. The choice of aniline with its dual function avoided the simultaneous use of a capping regent and a toxic reductant. The as-synthesized nanoplatelets have a large size of more than 900 × 500 nm(2) and a small thickness of 15...
May 17, 2017: Nanotechnology
Guangbao Wu, Zhi-Guo Zhang, Yongfang Li, Caiyan Gao, Xin Wang, Guangming Chen
Taking advantages of high electrical conductivity of single-walled carbon nanotube (SWCNT) and large Seebeck coefficient of rylene diimide, a convenient strategy is proposed to achieve high-performance n-type thermoelectric (TE) composites containing SWCNT and amino-substituted perylene diimide (PDINE) or naphthalene diimide (NDINE)). The obtained n-type composites display greatly enhanced TE performance with the maximum power factors of 112±8 (PDINE/SWCNT) and 135±14 (NDINE/SWCNT) μW m-1 K-2. A short doping time of 0...
May 16, 2017: ACS Nano
Da Hwi Gu, Seungki Jo, Hyewon Jeong, Hyeong Woo Ban, Sung Hoon Park, Seung Hwae Heo, Fredrick Kim, Jeong In Jang, Ji Eun Lee, Jae Sung Son
Electronically doped nanoparticles formed by incorporation of impurities have been of great interest because of their controllable electrical properties. However, the development of a strategy for n-type or p-type doping on sub-10 nm-sized nanoparticles under the quantum confinement regime is very challenging using conventional processes owing to the difficulty in synthesis. Herein, we report the colloidal chemical synthesis of sub-10 nm-sized Te-doped Bi nanoparticles with precisely controlled Te content from 0% to 5% and systematically investigate their low-temperature charge transport and thermoelectric properties...
May 16, 2017: ACS Applied Materials & Interfaces
Antonino Proto, Marek Penhaker, Silvia Conforto, Maurizio Schmid
Humans generate remarkable quantities of energy while performing daily activities, but this energy usually dissipates into the environment. Here, we address recent progress in the development of nanogenerators (NGs): devices that are able to harvest such body-produced biomechanical and thermal energies by exploiting piezoelectric, triboelectric, and thermoelectric physical effects. In designing NGs, the end-user's comfort is a primary concern. Therefore, we focus on recently developed materials giving flexibility and stretchability to NGs...
May 12, 2017: Trends in Biotechnology
Keiko Kikuchi, Kodai Yamamoto, Naoyuki Nomura, Akira Kawasaki
Magnesium silicide (Mg2Si)/carbon nanotube (CNT) thermoelectric nanofibers for use as a flexible thermoelectric material were successfully synthesized through the combined processes of the sol-gel method, magnesiothermic reduction, and liquid-solid phase reaction. In the resulting product, each CNT was coated with Mg2Si which was an approximately 60-nm-thick single crystal. The synthesized Mg2Si-coated CNTs exhibited n-type thermoelectric behavior confirming that n-type thermoelectric composite nanofibers were successfully obtained...
December 2017: Nanoscale Research Letters
Brandon Bonham, Gregory Guisbiers
Silicon-germanium is an important alloy mainly used in thermoelectricity and electronics. However, its thermal and optical properties still need further investigation at the nanoscale. That is why in this study, the size and shape effect on the silicon-germanium phase diagram is investigated through the nano-thermodynamics methodology. As expected, the phase diagram undergoes a shift down in temperature when the size decreases. However, it is demonstrated and explained why the size effect on the solidus-liquidus curves is much stronger than the one on the miscibility gap...
May 11, 2017: Nanotechnology
V R Akshay, M V Suneesh, M Vasundhara
Here, we report a simple, cost-effective, surfactant-assisted, and aqueous-based low-temperature reflux method for the synthesis of Bi2Te3 nanocrystals. Thermoelectric properties of n-type bismuth telluride (BT) nanostructures are reported by varying the morphology and crystal structure. Tuning the reaction time from 1 to 36 h enables the phase transformation from BiTe with a hexagonal crystal structure to Bi2Te3 with a rhombohedral crystal structure, which is evident from the refined X-ray diffraction results and high-resolution transmission electron microscopy analysis...
May 10, 2017: Inorganic Chemistry
Hye Jin Lee, Dae-Han Jung, Tae-Hyeon Kil, Sang Hyeon Kim, Ki-Suk Lee, Seung-Hyub Baek, Won Jun Choi, Jeong Min Baik
A facile method to fabricate a mechanically robust, stretchable solar absorber for stretchable heat generation and an enhanced thermoelectric generator (TEG) is demonstrated. This strategy is very simple: it uses a multilayer film made of titanium and magnesium fluoride optimized by a two-dimensional finite element frequency-domain simulation, followed by the application of mechanical stresses such as bending and stretching to the film. This process produces many microsized sheets with submicron thickness (∼500 nm), showing great adhesion to any substrates such as fabrics and polydimethylsiloxane...
May 19, 2017: ACS Applied Materials & Interfaces
Xinyu Wang, Yang Hong, Paddy K L Chan, Jingchao Zhang
Two-dimensional (2D) hybrid materials have drawn enormous attentions in thermoelectric applications. In this work, we apply molecular dynamics (MD) simulation to investigate the phonon thermal transport in silicene-germanene superlattice. A non-monotonic thermal conductivity of silicene-germanene superlattice with period length is revealed, which is due to the coherent-incoherent phonon conversion and phonon confinement mechanisms. We also calculate the thermal conductivity of Si-Ge random mixing monolayer, showing a U-shaped trend...
May 9, 2017: Nanotechnology
Andrew Gaul, Qing Peng, David J Singh, Ganpati Ramanath, Theodorian Borca-Tasciuc
First-principles calculations revealing insulator-to-metal transitions in Bi2Te3 and Bi2Te2Se, at 9 GPa and 12.5 GPa, respectively, match with prior experiments. Our electronic band structure calculations and accompanying Boltzmann transport calculations of thermoelectric properties for Bi2-xSbxTe2-ySey alloys explain and predict large power factor changes induced by pressure. Complex band degeneracy changes preceding insulator-to-metal transitions significantly alter the density of states near the Fermi level, and foster the disentangling of the unfavorable coupling between Seebeck coefficient and electrical conductivity...
May 24, 2017: Physical Chemistry Chemical Physics: PCCP
Qian Zhang, Zhiguang Cui, Zhiyong Wei, Siang Yee Chang, Lin Yang, Yang Zhao, Yang Yang, Zhe Guan, Youfei Jiang, Jason Fowlkes, Juekuan Yang, Dongyan Xu, Yunfei Chen, Terry T Xu, Deyu Li
Nanowires of complex morphologies, such as kinked wires, have been recently synthesized and demonstrated for novel devices and applications. However, the effects of these morphologies on thermal transport have not been well studied. Through systematic experimental measurements, we show that single-crystalline, defect-free kinks in boron carbide nanowires can pose a thermal resistance up to ∼30 times larger than that of a straight wire segment of equivalent length. Analysis suggests that this pronounced resistance can be attributed to the combined effects of backscattering of highly focused phonons and required mode conversion at the kink...
May 11, 2017: Nano Letters
Dimple, Nityasagar Jena, Abir De Sarkar
Strain and temperature induced tunability in the thermoelectric properties in monolayer MoS2 (ML-MoS2) has been demonstrated using density functional theory coupled to semi-classical Boltzmann transport theory. Compressive strain, in general and uniaxial compressive strain (along the zig-zag direction), in particular, is found to be most effective in enhancing the thermoelectric power factor, owing to the higher electronic mobility and its sensitivity to lattice compression along this direction. Variation in the Seebeck coefficient and electronic band gap with strain is found to follow the Goldsmid-Sharp relation...
June 7, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
D D Fan, H J Liu, L Cheng, J Zhang, P H Jiang, J Wei, J H Liang, J Shi
Using the first-principles pseudopotential method and Boltzmann transport theory, we give a comprehensive understanding of the electronic and phonon transport properties of the thermoelectric material BiCuSeO. By choosing an appropriate hybrid functional for the exchange-correlation energy, we find that the system is a semiconductor with a direct band gap of ∼0.8 eV, which is quite different from those obtained previously using standard functionals. Detailed analysis of a three-dimensional energy band structure indicates that there is a valley degeneracy of eight around the valence band maximum, which leads to a sharp density of states and is responsible for a large p-type Seebeck coefficient...
May 24, 2017: Physical Chemistry Chemical Physics: PCCP
Huimin Wang, Guangzhao Qin, Guojian Li, Qiang Wang, Ming Hu
Two-dimensional (2D) materials have attracted tremendous interest due to their fascinating physical and chemical properties and promising applications in nano-electronics, where thermal transport plays a vital role in determining the performance of devices. In this paper, we present a first-principles study of the thermal transport properties of monolayer zinc oxide (ZnO), which has potential applications in nano-electronics and thermoelectrics. The thermal conductivity of monolayer ZnO is found to be as low as 4...
May 24, 2017: Physical Chemistry Chemical Physics: PCCP
Jonathan M Skelton, Lee A Burton, Adam J Jackson, Fumiyasu Oba, Stephen C Parker, Aron Walsh
We present an in-depth first-principles study of the lattice dynamics of the tin sulphides SnS2, Pnma and π-cubic SnS and Sn2S3. An analysis of the harmonic phonon dispersion and vibrational density of states reveals phonon bandgaps between low- and high-frequency modes consisting of Sn and S motion, respectively, and evidences a bond-strength hierarchy in the low-dimensional SnS2, Pnma SnS and Sn2S3 crystals. We model and perform a complete characterisation of the infrared and Raman spectra, including temperature-dependent anharmonic linewidths calculated using many-body perturbation theory...
May 17, 2017: Physical Chemistry Chemical Physics: PCCP
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