1,720,978 research outputs found
Efectul interacţiunilor între lanţurile moleculare asupra proprietăţilor termoelectrice ale cristalelor nanostructurate de TTT2I3 și TTT(TCNQ)2
Get PDFTeza de doctor & AutoreferatScopul tezei este modelarea și analiza proprietăților termoelectrice ale cristalelor organice cvasiunidimensionale de TTT2I3 și TTT(TCNQ)2 și determinarea parametrilor optimali pentru obținerea eficienței termoelectrice maxime. Obiectivele sânt: elaborarea unui model fizic mai complet pentru cercetarea fenomenelor de transport; deducerea ecuației cinetice de tip Boltzmann și modelarea numerică a proprietăților termoelectrice ale cristalului; elaborarea de recomandări pentru realizarea experimentală
Thermoelectric Properties of a p-n Module Based on TTT2I3 and TTT(TCNQ)2 Organic Crystals
No full textIn this paper the thermoelectric properties of p – n thermoelectric module of organic nanostructured crystals is investigated. A thermoelectric module (TM) is a device designed for direct conversion of heat to electricity or for cooling effect by applying a small electrical current at the pairs legs. TMs are embedded in a various of devices: thermal generators for energy harvesting at industrial scale, personalized mini devices for power generation or local cooling effect for integrated circuits. In modern medical devices, TMs are used for accurate temperature control in PCR (polymerase chain reaction), biological samples and vaccines transportation, continuous temperature monitoring and others. However, most commercialized TMs nowadays are made of inorganic compounds with a low rate of energy conversion. By the other side, organic materials are more reliable, flexible with a higher efficiency at low temperature gradients. Earlier, it was established theoretically that organic crystals of TTT2I3 of p – type and TTT(TCNQ)2 of n– type are very prospective materials for thermoelectric applications at near-to-room temperature. For temperatures not exceeding ~ 400 K, it is expected that crystals properties will not change significantly. The charge transport and thermoelectric properties are predicted to significantly enhance by some manipulations with carrier and impurity concentrations. In the following, the electrical conductivity, the output voltage, and the maximum power factor of a p-n module made of these crystals is calculated numerically for different combinations of crystals parameters and temperature gradients
Enhancement of thermoelectric power factor in crystals of tetrathiotetracene iodide
Get PDFIn this paper we analyze the usefulness of quasi-one-dimensional organic crystals of TTT2I3
as material for a thermoelectric generator or thermoelectric cooler. Therefore, the hermoelectric power factor is calculated in the frame of a more complete three-dimensional physical model, for different values of carrier concentration and purity level. It is demonstrated that the power factor of the crystal can be increased significantly, if some optimizing rocedures are applied. These include the decrease of carrier concentration in comparison with the stoichiometric one and further purification
Analiza comportamentului fononilor în cristale quasi-unidimensionale de TTT(TCNQ)2 în apropierea tranziției structurale Peierls în aproximația 3D
Get PDFThis research paper focuses on investigating the metal-insulator transition occurring in quasi-one-dimensional organic crystals of TTT(TCNQ)2. The study utilizes a 3D approximation approach and introduces a physical model that incorporates two essential electron-phonon interactions. The first interaction is akin to the deformation potential, while the second interaction follows a polaron type behavior. By employing the random phase approximation, the renormalized phonon spectrum is calculated across different temperatures and various values of the dimensionless Fermi momentum kF. The findings indicate that the transition exhibits characteristics of the Peierls type, and the critical temperature associated with the Peierls transition is determined. Furthermore, an interesting observation is made that the Peierls critical temperature experiences a notable decrease with an increase in carrier concentration.Articolul se concentrează pe investigarea tranziției metal-dielectric care are loc în cristalele organice quasi-unidimensionale de TTT(TCNQ)2. Studiul utilizează o abordare de aproximare 3D și introduce un model fizic care încorporează două interacțiuni esențiale electron-fonon. Prima interacțiune este asemănătoare cu potențialul de deformare, în timp ce a doua interacțiune urmează un comportament de tip polaron. Utilizînd aproximația fazelor aleatorii, spectrul renormat al fononilor este calculat la diferite temperaturi și diferite valori ale impulsului adimensional Fermi kF. Constatările indică faptul că tranziția prezintă caracteristici de tip Peierls, iar temperatura critică asociată cu tranziția Peierls este determinată. Mai mult, se face o observație interesantă că temperatura critică Peierls înregistrează o scădere notabilă cu o creștere a concentrației purtătorilor
Thermoelectric properties of a thermoelectric module made of TTT2I3 and TTT(TCNQ)2 organic crystals
Get PDFIn this study, we conduct a comprehensive examination of the thermoelectric characteristics observed in crystals of TTT2I3, which exhibit p-type behavior, and TTT(TCNQ)2, functioning as an n-type conductor. These crystals have demonstrated adjustable thermoelectric properties by controlling the stoichiometry of charge carriers and impurity concentrations. TTT2I3 crystals, structured with alternating layers of tetrathiotetracene and iodide, display effective charge transport along the primary crystallographic axis. Similarly, TTT(TCNQ)2 shares the layeredarchitecture of TTT2I3 but with electron conductivity facilitated by TCNQ chains. In this investigation, we developed a theoretical model incorporating electron-phonon interactions and impurity scattering to analyze transport and thermoelectric characteristics
Thermoelectric properties of p-type TTT2I3 organic crystals as a function of temperature
Get PDFOnly AbstractNanostructured organic materials of tetrathiotetracene-iodide (TTT2I3) are very prospective p – type thermoelectric material. The internal structure is pronounced quasi-one dimensional, with molecular chains spaced at ~1 nm one from other. The charge transport takes place mainly along the chains, with rare phonon-assisted jumps between the chains. Earlier, the thermoelectric properties of this organic compound were estimated numerically in the frame of a detailed physical model, considering the most important internal interactions, as well as the weak interchain interactions. It was demonstrated [1] that important results could be obtained in TTT2I3 crystals after optimisation of some internal parameters of the crystal. However, the mentioned results were obtained for room temperature. For real applications, it is very important to investigate the temperature effects of the thermoelectric characteristics of TTT2I3 crystals. The obtained results are indicating that the thermoelectric power factor can be significantly enhanced for a wide range of crystal temperatures
Promising Organic Thermoelectric Material of n-Type
Get PDFSursa: Conferința – „Masa rotundă "Multidisciplinarity in Modern Science for the Benefit of Society", 21-22 septembrie 2017.→ https://ibn.idsi.md/ro/collection_view/36In this paper, the thermoelectric properties of n-type organic crystals of tetrathiotetracene-tetracyanoquinodimethane, TTT(TCNQ)2, are modeled in addition to
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Nanostructured TTT(TCNQ)2 Organic Crystals as Promising Thermoelectric n-Type Materials: 3D Modeling
No full textAccess full text – https://doi.org/10.1007/s11664-015-4018-8The thermoelectric properties of quasi-one-dimensional TTT(TCNQ)2 organic crystals have been investigated to assess the prospect of using this type of compound as an n-type thermoelectric material. A three-dimensional (3D) physical model was elaborated. This takes into account two of the most important interactions of conduction electrons with longitudinal acoustic phonons—scattering of the electrons’ by neighboring molecular chains and scattering by impurities and defects. Electrical conductivity, thermopower, power factor, electronic thermal conductivity, and thermoelectric figure of merit in the direction along the conducting molecular chains were calculated numerically for different crystal purity. It was shown that in stoichiometric compounds the thermoelectric figure of merit ZT remains small even after an increase of crystal perfection. The thermoelectric properties may be significantly enhanced by simultaneous increases of crystal perfection and electron concentration. The latter can be achieved by additional doping with donors. For less pure crystals, the interaction with impurities dominates the weak interchain interaction and the simpler one-dimensional (1D) physical model is applicable. When the impurity scattering is reduced, the interchain interaction begins to limit carrier mobility and use of the 3D physical model is required. The optimum properties enabling prediction of ZT ∼ 1 were determined
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