Perspectives on thermoelectrics: from fundamentals to device applications

This review is an update of a previous review (A. J. Minnich, et al., Energy Environ. Sci., 2009, 2, 466) published two years ago by some of the co-authors, focusing on progress made in thermoelectrics over the past two years on charge and heat carrier transport, strategies to improve the thermoelectric figure of merit, with new discussions on device physics and applications, and assessing challenges on these topics. Understanding of phonon transport in bulk materials has advanced significantly as the first-principles calculations are applied to thermoelectric materials, and experimental tools are being developed. Some new strategies have been developed to improve electron transport in thermoelectric materials. Fundamental questions on phonon and electron transport across interfaces and in thermoelectric materials remain. With thermoelectric materials reaching high ZT values well above one, the field is ready to take a step forward and go beyond the materials' figure of merit. Developing device contacts and module fabrication techniques, developing a platform for efficiency measurements, and identifying applications are becoming increasingly important for the future of thermoelectrics.MIT Energy InitiativeSolid-State Solar-Thermal Energy Conversion Center (funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-FG02-09ER46577)United States. Dept. of Energy (DOE Grant No. DE-FG02-08ER46516)Robert Bosch Gmb

Monte Carlo Simulation of Electron Transport in Degenerate Semiconductors

A modified algorithm is proposed to include Pauli exclusion principle in Monte-Carlo simulations. This algorithm has significant advantages to implement in terms of simplicity, speed and memory storage. We show that even in moderately high applied fields, one can estimate electronic distribution with a shifted Fermi sphere without introducing significant errors. Furthermore, the free-flights must be coupled to state availability constraints; this leads to substantial decrease in carrier heating at high fields. We give the correct definition for electronic temperature and show that in high applied fields, the quasi Fermi level is valley dependent. The effect of including Pauli exclusion principle on the band profile; electronic temperature and quasi Fermi level for inhomogeneous case of a single barrier heterostructure is illustrated

Assessment of different anther culture approaches to produce doubled haploids in cucumber (Cucumis sativus L.)

[EN] Cucumber is one of the most important vegetable crops worldwide, which makes it a good candidate to produce doubled haploid (DH) lines to accelerate plant breeding. Traditionally, these approaches involved induction of gynogenesis or parthenogenesis with irradiated pollen, which carries some disadvantages compared to androgenesis. Despite this, studies on anther/microspore cultures in cucumber are surprisingly scarce. Furthermore, most of them failed to unambiguously demonstrate the haploid origin of the individuals obtained. In this work we focused on anther cultures using two cucumber genotypes, different previously published protocols for anther culture, different in vitro culture variants to make it more efficient, and most importantly, a combination of flow cytometry and microsatellite molecular markers to evaluate the real androgenic potential and the impact of anther wall tissue proliferation. We developed a method to produce DH plants involving a bud pretreatment at 4 C, a 35 C treatment to anthers, culture with BAP and 2,4-D, and induction of callus morphogenesis by an additional 35 C treatment and sequential culture first in liquid medium in darkness and second in solid medium with light. We also found that factors such as genotype, proliferation of anther wall tissues, orientation of anthers in the culture medium and growth regulator composition of the initial anther culture medium have a remarkable impact. Our rate of chromosome doubling (81%) was high enough to exclude additional chromosome doubling steps. Together, our results present androgenesis as an improvable but yet more convenient alternative to traditional gynogenesis and parthenogenesis-based approaches.Thanks are due to all the whole staff of the Cell Biology Group for helping and training AA during his stay in the group. This work was supported by Grant AGL2017- 88135-R to JMSS from Spanish Ministerio de Economı´a y Competitividad (MINECO) jointly funded by FEDER.Asadi, A.; Zebarjadi, A.; Abdollahi, MR.; Seguí-Simarro, JM. (2018). Assessment of different anther culture approaches to produce doubled haploids in cucumber (Cucumis sativus L.). Euphytica. 214(216):1-17. https://doi.org/10.1007/s10681-018-2297-xS117214216Abdollahi MR, Najafi S, Sarikhani H, Moosavi SS (2016) Induction and development of anther-derived gametic embryos in cucumber (Cucumis sativus L.) by optimizing the macronutrient and agar concentrations in culture medium. Turk J Biol 40(3):571–579Ashok Kumar HG, Murthy HN (2004) Effect of sugars and amino acids on androgenesis of Cucumis sativus. Plant Cell, Tissue Organ Cult 78(3):201–208. https://doi.org/10.1023/b:ticu.0000025637.56693.68Bai B, Su YH, Yuan J, Zhang XS (2013) Induction of somatic embryos in arabidopsis requires local YUCCA expression mediated by the down-regulation of ethylene biosynthesis. Mol Plant 6(4):1247–1260. https://doi.org/10.1093/mp/sss154Claveria E, Garcia-Mas J, Dolcet-Sanjuan R (2005) Optimization of cucumber doubled haploid line production using in vitro rescue of in vivo induced parthenogenic embryos. J Am Soc Hortic Sci 130(4):555–560Corral-Martínez P, Nuez F, Seguí-Simarro JM (2011) Genetic, quantitative and microscopic evidence for fusion of haploid nuclei and growth of somatic calli in cultured ms1035 tomato anthers. Euphytica 178(2):215–228. https://doi.org/10.1007/s10681-010-0303-zDanin-Poleg Y, Reis N, Tzuri G, Katzir N (2001) Development and characterization of microsatellite markers in Cucumis. 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Int J Agric Crop Sci 5(10):1089Kurtar ES, Balkaya A, Kandemir D (2016) Evaluation of haploidization efficiency in winter squash (Cucurbita maxima Duch.) and pumpkin (Cucurbita moschata Duch.) through anther culture. Plant Cell, Tissue Organ Cult 127(2):497–511. https://doi.org/10.1007/s11240-016-1074-6Lotfi M, Alan AR, Henning MJ, Jahn MM, Earle ED (2003) Production of haploid and doubled haploid plants of melon (Cucumis melo L.) for use in breeding for multiple virus resistance. Plant Cell Rep 21(11):1121–1128Metwally EI, Moustafa SA, El-Sawy BI, Shalaby TA (1998) Haploid plantlets derived by anther culture of Cucurbita pepo. Plant Cell, Tissue Organ Cult 52(3):171–176. https://doi.org/10.1023/a:1005908326663Mohamed M, Refaei E (2004) Enhanced haploids regeneration in anther culture of summer squash (Curcurbita pepo L.). Cucurbit Genet Coop Rep 27:57–60Murashige T, Skoog F (1962) A revised medium for rapid growth and bioassays with tobacco tissue cultures. Physiol Plant 15:473–479Parra-Vega V, Renau-Morata B, Sifres A, Seguí-Simarro JM (2013) Stress treatments and in vitro culture conditions influence microspore embryogenesis and growth of callus from anther walls of sweet pepper (Capsicum annuum L.). Plant Cell, Tissue Organ Cult 112(3):353–360. https://doi.org/10.1007/s11240-012-0242-6Rakha M, Metwally E, Moustafa S, Etman A, Dewir Y (2012) Evaluation of regenerated strains from six Cucurbita interspecific hybrids obtained through anther and ovule in vitro cultures. Aust J Crop Sci 6(1):23–30Saghai-Maroof MA, Soliman KM, Jorgensen RA, Allard RW (1984) Ribosomal DNA spacer-length polymorphisms in barley: mendelian inheritance, chromosomal location, and population dynamics. Proc Natl Acad Sci USA 81(24):8014–8018. https://doi.org/10.1073/pnas.81.24.8014Sauton A, Dumas de Vaulx R (1987) Obtention de plantes haploides chez melon (Cucumis melo L.) par gynogenese indute par du pollen irraidié. Agronomie 7:141–148Seguí-Simarro JM (2016) Androgenesis in solanaceae. In: Germanà MA, Lambardi M (eds) In vitro embryogenesis. Methods in molecular biology, vol 1359. Springer, New York, pp 209–244. https://doi.org/10.1007/978-1-4939-3061-6_9Seguí-Simarro JM, Nuez F (2006) Androgenesis induction from tomato anther cultures: callus characterization. Acta Hort 725:855–861Seguí-Simarro JM, Nuez F (2007) Embryogenesis induction, callogenesis, and plant regeneration by in vitro culture of tomato isolated microspores and whole anthers. J Exp Bot 58(5):1119–1132Seguí-Simarro JM, Nuez F (2008) Pathways to doubled haploidy: chromosome doubling during androgenesis. Cytogenet Genome Res 120(3–4):358–369. https://doi.org/10.1159/000121085Shalaby TA (2006) Embryogenesis and plantlets regeneration from anther culture of squash plants (Cucurbita pepo L.) as affected by different genotypes. 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Experimental Determination of the Lorenz Number in Cu0.01Bi2Te2.7Se0.3 and Bi0.88Sb0.12

Nanostructuring has been shown to be an effective approach to reduce the lattice thermal conductivity and improve the thermoelectric figure of merit. Because the experimentally measured thermal conductivity includes contributions from both carriers and phonons, separating out the phonon contribution has been difficult and is mostly based on estimating the electronic contributions using the Wiedemann-Franz law. In this paper, an experimental method to directly measure electronic contributions to the thermal conductivity is presented and applied to Cu0.01Bi2Te2.7Se0.3, [Cu0.01Bi2Te2.7Se0.3]0.98Ni0.02, and Bi0.88Sb0.12. By measuring the thermal conductivity under magnetic field, electronic contributions to thermal conductivity can be extracted, leading to knowledge of the Lorenz number in thermoelectric materials

Thermoelectric transport perpendicular to thin film heterostructures using Monte Carlo technique

The Monte Carlo technique is used to calculate electrical as well as thermoelectric transport properties across thin film heterostructures. We study a thin InGaAsP barrier layer sandwiched between two InGaAs contact layers, when the barrier thickness is in 50nm-2000nm range. We found that with decreasing size, the effective Seebeck coefficient is increased substantially. The transition between pure ballistic thermionic transport and fully diffusive thermoelectric transport is also described

Combinatorial approach to identify electronically cloaked hollow nanoparticles

The possibility of designing core-shell nanoparticles that are “invisible” to the conduction electrons has been demonstrated recently. A total scattering cross section smaller than 0.01% of the physical cross section was demonstrated by artificially adjusting the parameters of the barrier and the well in a core-shell geometry. In this paper, we aim to extend the developed concept and find realistic material combinations that satisfy the cloaking criteria. We report designs of hollow nanoparticles that could be used to realize the cloaking concept in III–V semiconductor host matrices. Such particles could be used in advanced materials design to enhance and tune the electrical and the thermoelectric properties of a given host matrix. This paper may also contribute to defect engineering by coating defect sites with a proper cloaking layer.United States. Dept. of Energy. Office of Basic Energy Sciences (Award DE-FG02-09ER46577

An electrochemical system for efficiently harvesting low-grade heat energy

Efficient and low-cost thermal energy-harvesting systems are needed to utilize the tremendous low-grade heat sources. Although thermoelectric devices are attractive, its efficiency is limited by the relatively low figure-of-merit and low-temperature differential. An alternative approach is to explore thermodynamic cycles. Thermogalvanic effect, the dependence of electrode potential on temperature, can construct such cycles. In one cycle, an electrochemical cell is charged at a temperature and then discharged at a different temperature with higher cell voltage, thereby converting heat to electricity. Here we report an electrochemical system using a copper hexacyanoferrate cathode and a Cu/Cu2+ anode to convert heat into electricity. The electrode materials have low polarization, high charge capacity, moderate temperature coefficients and low specific heat. These features lead to a high heat-to-electricity energy conversion efficiency of 5.7% when cycled between 10 and 60 degrees C, opening a promising way to utilize low-grade heat.open121