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Dazhen Huang, Huiying Yao, Yutao Cui, Ye Zou, Fengjiao Zhang, Chao Wang, Hongguang Shen, Wenlong Jin, Jia Zhu, Ying Diao, Wei Xu, Chong-An Di, Daoben Zhu
Conjugated backbones play a fundamental role in determining the electronic properties of organic semiconductors. Based on two solution-processable dropyrrolo[3,4-c]pyrrole-1,4-diylidene)bis(thieno[3,2-b]thiophene derivatives with aromatic and quinoid structures, we have carried out a systematic study of the relationship between the conjugated-backbone structure and the thermoelectric properties. In particular, a combination of UV-vis-NIR spectra, photoemission spectroscopy and doping optimization are utilized to probe the interplay between energy levels, chemical doping, and thermoelectric performance...
August 18, 2017: Journal of the American Chemical Society
Jiangang He, Cesare Franchini
In this paper we assess the predictive power of the self-consistent hybrid functional scPBE0 in calculating the band gap of oxide semiconductors. The computational procedure is based on the self-consistent evaluation of the mixing parameter α by means of an iterative calculation of the static dielectric constant using the perturbation expansion after discretization (PEAD) method and making use of the relation α = 1/ε<sub>∞</sub>. Our materials dataset is formed by 30 compounds covering a wide range of band gaps and dielectric properties, and includes materials with a wide spectrum of application as thermoelectrics, photocatalysis, photovoltaics, transparent conducting oxides, and refractory materials...
August 16, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Yoshiyuki Nonoguchi, Shunsuke Sudo, Atsushi Tani, Tomoko Murayama, Yuriko Nishiyama, Ryoko M Uda, Tsuyoshi Kawai
This study investigates the hydride-mediated electron transfer doping of single-walled carbon nanotubes using absorption spectroscopy and thermoelectric measurements. Specific solvent basicity is found to be important for the efficient n-type doping of carbon nanotubes. This progress is an essential requirement for the future development of electronic and energy devices.
August 16, 2017: Chemical Communications: Chem Comm
Giselle A Elbaz, Wee-Liat Ong, Evan Ambrose Doud, Philip Kim, Daniel W Paley, Xavier Roy, Jonathan A Malen
Thermal management plays a critical role in the design of solid state materials for energy conversion. Lead halide perovskites have emerged as promising candidates for photovoltaic, thermoelectric and optoelectronic applications but their thermal properties are still poorly understood. Here we report on the thermal conductivity, elastic modulus, and sound speed of a series of lead halide perovskites MAPbX3 (X = Cl, Br, I), CsPbBr3, and FAPbBr3 (MA = methylammonium, FA = formamidinium). Using frequency domain thermoreflectance, we find that the thermal conductivities of single crystal lead halide perovskites range from 0...
August 14, 2017: Nano Letters
Akira Aiba, Firuz Demir, Satoshi Kaneko, Shintaro Fujii, Tomoaki Nishino, Kazuhito Tsukagoshi, Alireza Saffarzadeh, George Kirczenow, Manabu Kiguchi
The thermoelectric voltage developed across an atomic metal junction (i.e., a nanostructure in which one or a few atoms connect two metal electrodes) in response to a temperature difference between the electrodes, results from the quantum interference of electrons that pass through the junction multiple times after being scattered by the surrounding defects. Here we report successfully tuning this quantum interference and thus controlling the magnitude and sign of the thermoelectric voltage by applying a mechanical force that deforms the junction...
August 11, 2017: Scientific Reports
Aniket Singha, Bhaskaran Muralidharan
Investigating in detail the physics of energy filtering through a single planar energy barrier in nanostructured thermoelectric generators, we reinforce the non-trivial result that the anticipated enhancement in generated power at a given efficiency via energy filtering is a characteristic of systems dominated by incoherent scattering and is absent in ballistic devices. In such cases, assuming an energy dependent relaxation time τ(E) = kE (r) , we show that there exists a minimum value r min beyond which generation can be enhanced by embedding nanobarriers...
August 11, 2017: Scientific Reports
Dafei Yuan, Dazhen Huang, Cheng Zhang, Ye Zou, Chong-An Di, Xiaozhang Zhu, Daoben Zhu
To achieve efficient n-type doping, we designed and synthesized three dopants, Cyc-DMBI-H, (2-Cyc-DMBI)2, and (2-Cyc-DMBI-Me)2 with precisely regulated electron-donating ability to dope a small molecule 2DQTT-o-OD with high electron mobility and ambient stability. An unexpectedly high power factor of 33.3 μW m(-1) K(-2) was obtained by the new dopant (2-Cyc-DMBI-Me)2. Notably, with the intrinsically low lateral thermal conductivity of 0.28 W m(-1) K(-1), the figure of merit was determined to be 0.02 at room temperature...
August 11, 2017: ACS Applied Materials & Interfaces
Chaochao Dun, Corey A Hewitt, Qi Li, Yang Guo, Qike Jiang, Junwei Xu, Gabriel Marcus, Drew C Schall, David L Carroll
Precise control of the selective growth of heterostructures with specific composition and functionalities is an emerging and extremely challenging topic. Here, the first investigation of the difference in binding energy between a series of metal-semiconductor heterostructures based on layered V2 -VI3 nanostructures is investigated by means of density functional theory. All lateral configurations show lower formation energy compared with that of the vertical ones, implying the selective growth of metal nanoparticles...
August 11, 2017: Advanced Materials
Guoying Chen, Bunhong Lai, Xuefei Mao, Tuanwei Chen, Miaomiao Chen
Hydride generation (HG) is an effective technique that eliminates interfering matrix species and enables hydride separation. Arsenic speciation analysis can be fulfilled by cryogenic trapping (CT) based on boiling points of resulting arsines using liquid nitrogen (LN2) as a coolant. In this work, LN2 was replaced by thermoelectric effect using a cryo-genic trap that consisted of a polytetrafluoroethylene (PTFE) body sandwiched by two Peltier modules. After the trap was precooled, the arsines flew along a zigzag channel in the body and reached a sorbent bed of 0...
August 10, 2017: Analytical Chemistry
Dan Zhang, Junyou Yang, Qinghui Jiang, Zhiwei Zhou, Xin Li, Jiwu Xin, Abdul Basit, Yangyang Ren, Xu He, Weijing Chu, Jingdi Hou
The effect of Al-, Ga-, and In-doping on the thermoelectric (TE) properties of Cu3SbSe4 has been comparatively studied on the basis of theoretical prediction and experimental validation. It is found that tiny Al/Ga/In substitution leads to a great enhancement of electrical conductivity with high carrier concentration and also large Seebeck coefficient due to the preserved high band degeneracy and thereby a remarkably high power factor. Ultimately, coupled with the depressed lattice thermal conductivity, all three elements (Al/Ga/In) substituted samples have obtained a highly improved thermoelectric performance with respect to undoped Cu3SbSe4...
August 17, 2017: ACS Applied Materials & Interfaces
H M Dong, L L Li, W Xu, J L Liu
We theoretically investigate on the thermoelectric (TE) transport properties of edge and bulk states in a temperature-driven two-dimensional (2D) topological insulator (TI) realized from CdTe/HgTe/CdTe quantum wells (QWs). It is found that the temperature can effectively drive a TI phase in CdTe/HgTe/CdTe QWs. We find that the TE transport properties of 2D TI can be governed by edge states, bulk states, or their interplay, depending on driving temperature and chemical potential of the system. Moreover, we find that the TE figure of merit ZT shows a peak at relatively low temperatures due to the competition between bulk and edge transports...
August 8, 2017: Scientific Reports
Tiejun Zhu, Yintu Liu, Chenguang Fu, Joseph P Heremans, Jeffrey G Snyder, Xinbing Zhao
No abstract text is available yet for this article.
August 2017: Advanced Materials
Sigurdur I Erlingsson, Andrei Manolescu, George Alexandru Nemnes, Jens H Bardarson, David Sanchez
We calculate the charge current generated by a temperature bias between the two ends of a tubular nanowire. We show that in the presence of a transversal magnetic field the current can change sign; i.e., electrons can either flow from the hot to the cold reservoir, or in the opposite direction, when the temperature bias increases. This behavior occurs when the magnetic field is sufficiently strong, such that Landau and snaking states are created, and the energy dispersion is nonmonotonic with respect to the longitudinal wave vector...
July 21, 2017: Physical Review Letters
Renshuang Zhai, Lipeng Hu, Haijun Wu, Zhaojun Xu, Tie-Jun Zhu, Xin-Bing Zhao
Bismuth-telluride-based solid solutions are the unique thermoelectric (TE) materials near room temperature. Various approaches have been applied to enhance the thermoelectric performance, and much progress has been made in their p-type materials. However, for the n-type counterparts, little breakthrough has been obtained. We herein report on enhancing thermoelectric performance of n-type bismuth-telluride-based alloys by nonstoichiometry to mediate the point defects, combined with one-time hot deformation. The improved power factor of 3...
August 15, 2017: ACS Applied Materials & Interfaces
Shaodong Sun, Pengju Li, Shuhua Liang, Zhimao Yang
As a significant metal chalcogenide, copper sulfide (Cu2-xS, 0 < x < 1), with a unique semiconducting and nontoxic nature, has received significant attention over the past few decades. Extensive investigations have been employed to the various Cu2-xS micro-/nanostructures owing to their excellent optoelectronic behavior, potential thermoelectric properties, and promising biomedical applications. As a result, micro-/nanostructured Cu2-xS with well-controlled morphologies, sizes, crystalline phases, and compositions have been rationally synthesized and applied in the fields of photocatalysis, energy conversion, in vitro biosensing, and in vivo imaging and therapy...
August 4, 2017: Nanoscale
Wei-Hsuan Hsu, Wan-Ting Chien
Titanium alloys have several advantages, such as a high strength-to-weight ratio. However, the machinability of titanium alloys is not as good as its mechanical properties. Many machining processes have been used to fabricate titanium alloys. Among these machining processes, electrical discharge machining (EDM) has the advantage of processing efficiency. EDM is based on thermoelectric energy between a workpiece and an electrode. A pulse discharge occurs in a small gap between the workpiece and electrode. Then, the material from the workpiece is removed through melting and vaporization...
November 24, 2016: Materials
Kaya Wei, Xiaoyu Zeng, Terry M Tritt, Artem R Khabibullin, Lilia M Woods, George S Nolas
Tin clathrate-II framework-substituted compositions are of current interest as potential thermoelectric materials for medium-temperature applications. A review of the literature reveals different compositions reported with varying physical properties, which depend strongly on the exact composition as well as the processing conditions. We therefore initiated an approach whereby single crystals of two different (K,Ba)16(Ga,Sn)136 compositions were first obtained, followed by grinding of the crystals into fine powder for low temperature spark plasma sintering consolidation into dense polycrystalline solids and subsequent high temperature transport measurements...
August 26, 2016: Materials
Ana Isabel Torres-Gómez, Enrique F Ledesma, Rocio Otero, José Maria Fernández, José Ramón Jiménez, Jorge de Brito
This work evaluates the effects of using non-conforming fly ash (Nc-FA) generated in a thermoelectric power plant as filler material for mortars made with natural sand (NA) and recycled sand from masonry waste (FRMA). The incorporation of powdered recycled masonry filler (R-MF) is also tested as an alternative to siliceous filler (Si-F). Three families of mortars were designed to study: the effect of replacing Si-F with Nc-FA on mortars made with NA; the effect of replacing Si-F with Nc-FA on mortars made with 50% of NA and 50% of FRMA; and the effect of replacing Si-F with R-MF on mortars made with NA and FRMA...
August 25, 2016: Materials
Susan M Kauzlarich, Fan Sui, Christopher J Perez
Earth abundant element clathrate phases are of interest for a number of applications ranging from photovoltaics to thermoelectrics. Silicon-containing type I clathrate is a framework structure with the stoichiometry A8-xSi46 (A = guest atom such as alkali metal) that can be tuned by alloying and doping with other elements. The type I clathrate framework can be described as being composed of two types of polyhedral cages made up of tetrahedrally coordinated Si: pentagonal dodecahedra with 20 atoms and tetrakaidecahedra with 24 atoms in the ratio of 2:6...
August 23, 2016: Materials
Dong Xue, Charles W Myles, Craig Higgins
Type II clathrates are interesting due to their potential thermoelectric applications. Powdered X-ray diffraction (XRD) data and density functional calculations for NaxSi136 found a lattice contraction as x increases for 0 < x < 8 and an expansion as x increases for x > 8. This is explained by XRD data that shows that as x increases, the Si28 cages are filled first for x < 8 and the Si20 cages are then filled for x > 8. Motivated by this work, here we report the results of first-principles calculations of the structural and vibrational properties of the Type II clathrate compounds AxSi136, AxGe136, and AxSn136...
August 11, 2016: Materials
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