‘Squeezing’ near-field thermal emission for ultra-efficient high-power thermophotovoltaic conversion

Karalis, Aristeidis; Joannopoulos, John D.

doi:10.1038/srep28472

Cited by 71 publications

(59 citation statements)

References 56 publications

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“…Recently, the far-field TR performance was theoretically analyzed by Strandberg [3], and was demonstrated experimentally by Santhanam and Fan [5] with a relatively low achieved efficiency. Motivated by thermophotovoltaic (TPV), where an emitter is placed between the heat source and the cold PV cell to reshape the photon emission spectrum [7][8][9][10][11][12][13][14][15], placing a heat sink between the hot TR cell and the cold environment is shown to enhance the performance of TR devices [6,16,17]. Using the impedance matching condition derived from Coupled-Mode Theory [18][19][20][21][22][23][24][25], it is shown that the emitter and the PV cell in the near-field setup should be designed as a whole to maximize the radiative energy transfer and therefore the power output [15,24,26].…”

Section: Introductionmentioning

confidence: 99%

Performance comparison between photovoltaic and thermoradiative devices

Lin

Wang

Teo

et al. 2017

Journal of Applied Physics

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Photovoltaic (PV) and thermoradiative (TR) devices are power generators that use the radiative energy transfer between a hot and a cold reservoir. For PV devices, the semiconductor at the cold side (PV cell) generates electric power; for TR devices, the semiconductor at the hot side (TR cell) generates electric power. In this work, we compare the performance of the photovoltaic and thermoradiative devices, with and without the non-radiative processes. Without non-radiative processes, PV devices generally produce larger output powers than TR devices. However, when non-radiative processes become important, the TR can outperform the PV devices. This conclusion applies to both far-field and near-field based devices. A key difference in efficiency between PV and TR devices is pointed out. Journal of Applied PhysicsThis work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy in whole or in part without payment of fee is granted for nonprofit educational and research purposes provided that all such whole or partial copies include the following: a notice that such copying is by permission of Mitsubishi Electric Research Laboratories, Inc.; an acknowledgment of the authors and individual contributions to the work; and all applicable portions of the copyright notice. Copying, reproduction, or republishing for any other purpose shall require a license with payment of fee to Mitsubishi Electric Research Laboratories, Inc. All rights reserved.Photovoltaic (PV) and thermoradiative (TR) devices are power generators that use the radiative energy transfer between a hot and a cold reservoir. For PV devices, the semiconductor at the cold side (PV cell) generates electric power; for TR devices, the semiconductor at the hot side (TR cell) generates electric power. In this work, we compare the performance of the photovoltaic and thermoradiative devices, with and without the non-radiative processes. Without non-radiative processes, PV devices generally produce larger output powers than TR devices. However, when non-radiative processes become important, the TR can outperform the PV devices. This conclusion applies to both far-field and near-field based devices. A key difference in efficiency between PV and TR devices is pointed out.

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Section: Introductionmentioning

confidence: 99%

Performance comparison between photovoltaic and thermoradiative devices

Lin

Wang

Teo

et al. 2017

Journal of Applied Physics

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“…The optical parameters of GaSb are calculated using a universal model for III–V semiconductors 25 . The emitter was chosen to be a plasmonic material with its plasmonic frequency slightly above the cell’s bandgap, which enables strong surface wave excitations in the designated frequency range to maximize the radiative transfer efficiency 11 . In this work, the optical parameters are taken from the experimental data of Ga:ZnO (GZO) 26 , which has an near-infrared (NIR) plasmonic frequency (1.38 × 10 15 rad/s) and high melting point to suit the requirement for a TPV emitter.…”

Section: Resultsmentioning

confidence: 99%

Simple Rectangular Gratings as a Near-Field “Anti-Reflection” Pattern for GaSb TPV Cells

Liu

Yang

et al. 2017

Sci Rep

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We show theoretically that 2D rectangular gratings on the surface of GaSb can serve as an “anti-reflection” pattern for nano-gap thermophotovoltaic (TPV) devices, which significantly enhances near-field radiative flux from the emitter to a GaSb cell, thus improving output power and conversion efficiency. The system in this study is a 200-nm gap TPV power generation system with a planar infrared plasmonic emitter and GaSb cell. Rigorous coupled-wave analysis is used to calculate the spectral near-field radiative flux involving periodic structures. The simulation shows that when coupled with a near-infrared plasmonic bulk emitter, adding gratings on the GaSb cell surface results in strong spectral enhancement above the cell’s bandgap and suppression for low-energy photon transmission, an effect that cannot be fully predicted by the effective medium theory. The resultant peak spectral heat flux is 2.8 times as high as the case without surface structures and the radiative transfer efficiency increased to 24.8% from the original 14.5% with the emitter temperature at 1800 K. The influence of the grating’s geometry parameters on the enhancement and peak frequency is further discussed with rigorous calculation of the spatial distribution of thermal radiative transfer that provided insight into the physical mechanism.

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“…These values lead to surface polariton resonance at 0.85 eV when sharing an interface with vacuum. This is similar to real materials such as titanium carbide (TiC) and tantalum silicide (TaSi 2 ) which have resonances at 0.9 eV and 0.8 eV, respectively [33]. The device is assumed to be azimuthally symmetric and infinite in the ρ -direction making the view factor unity between the emitter and the cell.…”

Section: Description Of the Problemmentioning

confidence: 90%

External Luminescence and Photon Recycling in Near-Field Thermophotovoltaics

2017

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The importance of considering near-field effects on photon recycling and spontaneous emission in a thermophotovoltaic device is investigated. Fluctuational electrodynamics is used to calculate external luminescence from a photovoltaic cell as a function of emitter type, vacuum gap thickness between emitter and cell, and cell thickness. The observed changes in external luminescence suggest strong modifications of photon recycling caused by the presence of the emitter. Photon recycling for propagating modes is affected by reflection at the vacuum-emitter interface and is substantially decreased by the leakage towards the emitter through tunneling of frustrated modes. In addition, spontaneous emission by the cell can be strongly enhanced by the presence of an emitter supporting surface polariton modes. It follows that using a radiative recombination model with a spatially uniform radiative lifetime, even corrected by a photon recycling factor, is inappropriate. Applying the principles of detailed balance, and accounting for non-radiative recombination mechanisms, the impact of external luminescence enhancement in the near field on thermophotovoltaic performance is investigated. It is shown that unlike isolated † Corresponding author. Tel.: + 1 801 581 5721 Email address: mfrancoeur@mech.utah.edu 2 cells, the external luminescence efficiency is not solely dependent on cell quality, but significantly increases as the vacuum gap thickness decreases below 400 nm for the case of an intrinsic silicon emitter. In turn, the open-circuit voltage and power density benefit from this enhanced external luminescence toward the emitter. This benefit is larger as cell quality, characterized by the contribution of non-radiative recombination, decreases.3

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‘Squeezing’ near-field thermal emission for ultra-efficient high-power thermophotovoltaic conversion

Cited by 71 publications

References 56 publications

Performance comparison between photovoltaic and thermoradiative devices

Performance comparison between photovoltaic and thermoradiative devices

Simple Rectangular Gratings as a Near-Field “Anti-Reflection” Pattern for GaSb TPV Cells

External Luminescence and Photon Recycling in Near-Field Thermophotovoltaics

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