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[en] The paper is devoted to the analysis of calibration results of thermoelectric voltage converter obtained by five participants of interlaboratory comparisons which ended in 2017. The analysis is accented on several aspects that led to inadequate deviation of results from the expected values. The attention is focused on the reasons for overestimation of measurement uncertainty reported by one of laboratories and the exceeding of the permissible value of criterion for assessing the competence of another laboratory at one observation point. Two variants of measurement schemes which were used by participants, are analyzed, main uncertainty sources are determined, uncertainty budgets are drawn up. The measurement model for a non-standardized measurement set-up is proposed, taking into account the drift of input and output signals. The logical conclusion of analysis is ascertainment of non-compliance with ISO/IEC 17025 recommendations and sufficient level lack of methodological support for these calibration laboratories. (author)
[en] We examine the effective properties of a thermoelectric material in the vicinity of an arbitrarily shaped hole. Using complex variable methods, we establish closed-form representations of the electric and thermal fields in the matrix surrounding the hole. Specifically, we analyze the effective material parameters of a rectangular thermoelectric region containing an insulated macroscopic hole and determine that the effective electric and thermal conductivities depend strongly on the size and shape of the hole while the effective Seebeck coefficient always remains equal to that of the surrounding matrix. Perhaps most significantly, we conclude that since an insulated hole has almost the same effect on both the effective electric and thermal conductivities, its introduction does not affect the effective thermoelectric figure of merit in most thermoelectric materials. Consequently, we can conclude that, for the most part, an arbitrarily shaped hole can be inserted into a thermoelectric material without decreasing its maximum thermoelectric conversion efficiency. Our findings provide an important theoretical basis for the future design and development of thermoelectric devices.
[en] Full text: The binary GeTe, SnTe, and PbTe compounds have attracted immense interest due to their applications as materials for data storage or thermoelectric energy conversion [1,2]. Due to low price and abundance associated to Si element, the substitution of Ge, Sn and Pb by Si can be considered has an excellent alternative. In this sense, here we reported an attempt of synthesis of the Si-Te system compounds by mechanical alloying. The main goal this work is the elucidation of the structural changes promoted by milling at a Si33Te6-4 mixture. Thus, the powders were milled up to 50 hours and its structure and composition evolution were studied by X-Ray Diffraction Analysis (XRD), method Rietveld and differential scanning calorimetry (DSC). The XRD results indicated that Fe atoms, coming from balls and jars, connects to Te atoms forming FeTe2 for longer milling times. A thermodynamic analysis can be explain this behavior as will be discussed. In addition, to understand structural changes promoted by milling time the pair distribution functions (PDF) was applied. (author)
[en] The basic characteristics of thermophotovoltaic heterostructure p-InAsSbP/n-InAs converters have been simulated. The converters have been designed so that a contact to the irradiated p-InAsSbP layer has a limited area or, in the flip-chip design, radiation is introduced through a contact-free part of the n+-InAs substrate. It has been shown that the design features of the converter influence its efficiency and active region temperature.
[en] The photovoltaic–thermal (PVT) systems have been established for providing both electricity and heat using the existing photovoltaic (PV) system set-up. The PVT systems capture panel heat for some useful purpose. It is based on deploying a polymer sheet at the back of the PV panel to accommodate cooling water between the PV panel and the sheet to maximize the contact area between cooling water and panel. The present work compares the performance of a normal PV panel to that of the novel PVT panel. The PVT system is fabricated and experiments are conducted to evaluate electrical and thermal efficiencies. An improvement of 2.17% is observed in the electrical efficiency of the PVT panel in comparison with the normal PV panel. A brief cost analysis along with payback period calculations of the PVT panel is also included. (author)
[en] Artificial nanostructures have improved prospects of thermoelectric systems by enabling selective scattering of phonons and demonstrating significant thermal conductivity reductions. While the low thermal conductivity provides necessary temperature gradients for thermoelectric conversion, the heat generation is detrimental to electronic systems where high thermal conductivity are preferred. The contrasting needs of thermal conductivity are evident in thermoelectric cooling systems, which call for a fundamental breakthrough. Here we show a silicon nanostructure with vertically etched holes, or holey silicon, uniquely combines the low thermal conductivity in the in-plane direction and the high thermal conductivity in the cross-plane direction, and that the anisotropy is ideal for lateral thermoelectric cooling. The low in-plane thermal conductivity due to substantial phonon boundary scattering in small necks sustains large temperature gradients for lateral Peltier junctions. The high cross-plane thermal conductivity due to persistent long-wavelength phonons effectively dissipates heat from a hot spot to the on-chip cooling system. Our scaling analysis based on spectral phonon properties captures the anisotropic size effects in holey silicon and predicts the thermal conductivity anisotropy ratio up to 20. Our numerical simulations demonstrate the thermoelectric cooling effectiveness of holey silicon is at least 30% greater than that of high-thermal-conductivity bulk silicon and 400% greater than that of low-thermal-conductivity chalcogenides; these results contrast with the conventional perception preferring either high or low thermal conductivity materials. The thermal conductivity anisotropy is even more favorable in laterally confined systems and will provide effective thermal management solutions for advanced electronics. (paper)
[en] Highlights: • DFT calculations of electronic and magnetic properties of d-metal trihalides are made. • It is shown these chain structures have weak interactions between individual chains. • All trihalides structures are conductive but MoBr3 is semiconductor. • d-metal atoms have magnetic moments in most of these structures. • Ferro- and antiferro- phases have same energies due to weak d-orbitals overlapping. - Abstract: Using DFT GGA calculations, electronic structure and magnetic properties of wide family of transition metal trihalides (TMHal3) (Zr, Ti and Nb iodides, Mo, Ru, Ti and Zr bromides and Ti or Zr chlorides) are investigated. These structures consist of transition metal atoms chains surrounded by halides atoms. Chains are connected to each other by weak interactions. All TMHal3 compounds were found to be conductive along chain axis except of MoBr3 which is indirect gap semiconductor. It was shown that NbI3 and MoBr3 have large magnetic moments on metal atoms (1.17 and 1.81 µB, respectively) but other TMHal3 materials have small or zero magnetic moments. For all structures ferromagnetic and anti-ferromagnetic phases have almost the same energies. The causes of these properties are debated.
[en] In the present study, CdZnS and Co (3%): CdZnS nanoparticles (NPs) have been synthesized via wet chemical method at room temperature using 1-thioglycerol as a capping agent. The incident photon-to-current conversion efficiency (IPCE) measurement has been carried out for Co (5%): CdZnS for the first time in this study. The results show that Co (3%): CdZnS can be utilized as sensitizers to improve the performance of solar cells. In addition to the photovoltaic properties; structural, optical and morphological properties of Co (3%): CdZnS NPs have been investigated. The results indicate that Co (3%): CdZnS NPs can be suitable material for photovoltaic applications. (author)
[en] Highlights: • A facile spray deposition technique to deposit the CuSCN HTM layer is developed. • The perovskite layer is not appreciably damaged during the spray deposition of CuSCN. • Perovskite solar cell (PSC) with the pristine CuSCN layer exhibits PCE of 17.10%. • PSCs with the CuSCN demonstrate remarkable long-term and thermal stabilities. By employing CuSCN, a low-cost inorganic hole transporting material (HTM), CH3NH3PbI3 perovskite solar cell (PSC) devices with high efficiency and extended stability were successfully fabricated in this work. In particular, we developed a facile method of depositing CuSCN layer reproducibly by a simple spray deposition technique, which allows the formation of the CuSCN layer without any significant damage of the underlying CH3NH3PbI3 layer. The fabricated PSC with ~50 nm-thick pristine CuSCN layer exhibits the photovoltaic conversion efficiency (PCE) of 17.10% with JSC of 23.10 mA/cm2, VOC of 1,013 mV and FF of 0.731. Compared with conventional PSCs based on spiro-OMETAD HTM, the PSC employing CuSCN exhibits higher value of JSC, suggesting that CuSCN transports holes more efficiently than spiro-OMETAD. Furthermore, PSCs employing the pristine CuSCN demonstrate a remarkable long-term stability at ambient condition with the decrease of PCE by only 5.8% after 100 days. In addition, the PCE decrease during the encapsulation process at 120 °C was merely 13%, which is much lower value than ~70% observed for the conventional device based on spiro-OMETAD, indicating excellent thermal stability of the CuSCN-based PSCs.