Interest in thermoelectrics for waste-heat recovery and localized cooling has flourished in recent years, but questions about cost and scalability remain unanswered. This work investigates the ...fabrication costs and coupled thermal and electrical transport factors that govern device efficiency and commercial feasibility of the most promising thermoelectric materials. For 30 bulk and thin film thermoelectric materials, we quantify the tradeoff between efficiency and cost considering electrical and thermal transport at the system level, raw material prices, system component costs, and estimated manufacturing costs. This work neglects the cost of heat, as appropriate for most waste-heat recovery applications, and applies a power generation cost metric in $/W and a cooling operating cost metric in $/kWh. The results indicate material costs are too high for typical thermoelectric power generation applications at mean temperatures below 135°C. Above 275°C, many bulk thermoelectric materials can achieve costs below $1/W. The major barrier to economical thermoelectric power generation at these higher temperatures results from system costs for heat exchangers and ceramic plates. For cooling applications, we find that several thermoelectric materials can be cost competitive and commercially promising.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Thermoelectric materials for power generation are typically compared using the dimensionless figure-of-merit ZTbecause it relates directly to the device efficiency. However, for practical ...applications, the cost of power generation - as governed by material, manufacturing, and heat exchanger costs - is also a critical factor which is not captured in ZTalone. The necessary analysis, derived herein, optimizes the coupled thermoelectric and economic problem for the leg length, L, and system fill factor, F, as functions of these costs. Fuel, operating, and maintenance costs are excluded. This optimization yields the minimum $ per W value for thermoelectric power generation and a framework for comparing materials beyond ZT. This analysis shows that even very expensive thermoelectric materials have the potential to be the most cost effective at the system level, if incorporated with sufficiently short legs and small fill factor. An approximate scaling analysis, verified using numerical calculations, gives the first closed-form, analytical expressions for optimal Land Fto minimize $ per W. The analysis also delineates various cost-dominant regimes with different priorities for materials development, including: (i) a heat exchanger cost dominated regime, where ZTshould be increased regardless of material or manufacturing costs; (ii) an areal cost, C'', dominated regime at fixed F, where ZT/C'' should be maximized, and (iii) a volumetric cost, C''', dominated regime at fixed F, where ZT/(kC''') should be maximized, reinforcing the need for low thermal conductivity, k. The cost-performance framework derived here will be applied to a number of real materials and applications in a separate manuscript.
This study reports on the thermoelectric properties of poly(3‐alkylchalcogenophene) thin films (500 nm) as a function of heteroatom (sulfur, selenium, tellurium), and how these properties change with ...dopant (ferric chloride) concentration. UV–vis–NIR spectroscopy shows that polaronic charge carriers are formed upon doping. Poly(3‐alkyltellurophene) (P3RTe) is most easily doped followed by poly(3‐alkylselenophene) (P3RSe) and poly(3‐alkylthiophene) (P3RT), where R = 3,7‐dimethyloctyl chain is the pendant alkyl group. Thermoelectric properties vary as functions of the heteroatom and doping level. At low dopant concentrations (≈1 × 10−3
m), P3RTe shows the highest power factor of 10 µW m−1 K−2, while, at higher dopant concentrations (≈5 × 10−3
m), P3RSe shows the highest power factor of 13 µW m−1 K−2. Most notably, it is found that the measured properties are consistent with Mott's polaron hopping model and not consistent with other transport models. Additionally, temperature‐dependent conductivity measurements show that for a given dopant concentration, the activation energies for electronic transport decrease as the heteroatom is changed from sulfur to selenium to tellurium. Overall, this work presents a systematic study of poly(chalcogenophenes) and indicates the potential of polymers beyond P3HT by tuning the heteroatom and doping level for optimized thermoelectric performance.
This work details the thermoelectric and charge transport properties of poly(3‐alkylchalcogenophene) thin‐films as a function of heteroatom (sulfur, selenium, tellurium), and how these properties change with dopant (ferric chloride) concentration. This systematic investigation correlates the identity of the heteroatom in polyheterocycles with the doping process, the resulting thermoelectric properties, and the charge transport mechanism.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The thermoelectric properties of a unique hybrid polymer-inorganic nanoparticle system consisting of tellurium nanowires and a conducting polymer, ...poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), can be optimized by both controlling the shape of the nanoparticles and the loading and doping of the polymeric matrix with polar solvents. The mechanism for an observed improvement in power factor is attributed to the unique conducting nature of PEDOT:PSS, which exhibits a transition from a hopping transport-dominated regime to a carrier scattering-dominated regime upon doping with polar solvents. Near this transition, the electrical conductivity can be improved without significantly reducing the thermopower. Relying on this principle, the power factor optimization for this new thermoelectric material is experimentally carried out and found to exceed 100 μW m(-1) K(-2), which is nearly five orders of magnitude greater than pure PEDOT:PSS.
Molecular doping is a powerful method to fine‐tune the thermoelectric properties of organic semiconductors, in particular to impart the requisite electrical conductivity. The incorporation of ...molecular dopants can, however, perturb the microstructure of semicrystalline organic semiconductors, which complicates the development of a detailed understanding of structure–property relationships. To better understand how the doping pathway and the resulting dopant counterion influence the thermoelectric performance and transport properties, a new dimer dopant, (N‐DMBI)2, is developed. Subsequently, FBDPPV is then n‐doped with dimer dopants (N‐DMBI)2, (RuCp*mes)2, and the hydride‐donor dopant N‐DMBI‐H. By comparing the UV–vis–NIR absorption spectra and morphological characteristics of the doped polymers, it is found that not only the doping mechanism, but also the shape of the counterion strongly influence the thermoelectric properties and transport characteristics. (N‐DMBI)2, which is a direct electron‐donating dopant with a comparatively small, relatively planar counterion, gives the best power factor among the three systems studied here. Additionally, temperature‐dependent conductivity and Seebeck coefficient measurements differ between the three dopants with (N‐DMBI)2 yielding the best thermoelectric properties. The results of this study of dopant effects on thermoelectric properties provide insight into guidelines for future organic thermoelectrics.
A novel dimeric n‐dopant (N‐DMBI)2, is designed and synthesized to understand the effects of molecular dopants on thermoelectric properties. This study shows how the counterion shape, and the doping mechanism affect the thermoelectric performance and the transport pathway of n‐type conducting polymers, and reveals what type of n‐dopant is preferable.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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•New cooling cycle uses polymers to convert humid air to dry air and liquid water.•Thermodynamic analysis reveals the limits to performance of the new cycle.•The new cycle can use ...lower temperature heat sources than traditional desiccants.•The new cycle can be more efficient than traditional desiccant cycles.•Liquid water harvesting is a useful byproduct of the new cycle.
We present a theoretical description for a new desiccant air conditioning cycle that uses thermoresponsive polymers instead of traditional desiccants. We use a combined first and second law analysis to demonstrate that this new cycle has three major advantages relative to the traditional case: (i) it can regenerate at lower temperatures, (ii) it can harvest liquid water and (iii) it has significantly higher coefficients of performance (COPs). For example, this new cycle can achieve a COP of 5.1 when regenerated at 95 °C, whereas the traditional desiccant cycle is limited to a COP of ∼ 1. The fundamental origins of these advantages can be traced to the method of regeneration. The traditional desiccant cycle regenerates by flowing hot air over the desiccant, which provides a medium for gaseous water desorption. However, this also generates entropy and places a minimum temperature constraint on the hot air. In contrast, the thermoresponsive polymer cycle regenerates through a polymer phase transition. The polymer absorbs water vapor in humid air, and then it expels liquid water when raised above its transition temperature. This regeneration method generates liquid water that can be harvested and relaxes constraints on entropy generation and minimum temperature. The minimum regeneration temperature of the thermoresponsive cycle is only limited by the transition temperature of the polymer, which can be tuned through materials science. Due to its liquid water harvesting capability, the new cycle potentially eliminates water consumption when used with evaporative cooling, or it can be directly used for atmospheric water harvesting.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZRSKP
The electrical behavior of a conducting‐polymer/inorganic‐nanowire composite is explained with a model in which carrier transport occurs predominantly through a highly conductive volume of polymer ...that exists at the polymer‐nanowire interface. This result highlights the importance of controlling nanoscale interfaces for thermoelectric materials, and provides a general route for improving carrier transport in organic/inorganic composites.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Various spectral control techniques can be applied to improve the performance of a thermophotovoltaic (TPV) device. For example, a back surface reflector (BSR) is a common structure to improve the ...performance of TPV devices. A conventional metal BSR structure enhances the photogeneration rate by increasing the absorption probability of photons via back surface reflections, affording a second chance for absorption. However, the effects of surface passivation and external luminescence introduced by BSR structures have been previously ignored, which potentially decreases the performance of TPV devices. Recently, a back gapped reflector (BGR) structure was proposed to greatly improve the performance of far-field TPV devices by reducing imperfect reflections at the semiconductor-metal interface. In the present work, the performance improvement on a thin-film, near-field InAs TPV device with a BGR is investigated, comparing its performance to that with a conventional metal BSR. Surface passivation conditions are also investigated to further improve the performance of TPV devices with back reflectors. The output power and efficiency are calculated using an iterative model combining fluctuational electrodynamics and the full drift-diffusion model. For the well-passivated condition, when the BSR is replaced by the BGR, the calculated conversion efficiency of the near-field TPV was improved from 16.4% to 21% and the output power was increased by 10%. Finally, the absorption of the back reflectors and external luminescence loss are analyzed to explain the performance improvement.
•Studied a thermophotovoltaic (TPV) cell with a back gapped reflector (BGR).•Used a photon-charge coupled iterative method to analyze near- and far-field TPVs.•The BGR can reduce the parasitic absorption and external luminescence losses.•Well-passivated surface can greatly improve the performance of TPVs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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