Thermodynamics of light management in near-field thermophotovoltaics

Abstract

We evaluate near-field thermophotovoltaic (TPV) energy conversion systems focusing in particular on their open-circuit voltage (Voc). Unlike previous analyses based largely on numerical simulations with fluctuational electrodynamics, here, we develop an analytic model that captures the physics of near-field TPV systems and can predict their performance metrics. Using our model, we identify two important opportunities of TPV systems operating in the near-field. First, we show analytically that enhancement of radiative recombination is a natural consequence of operating in the nearfield. Second, we note that, owing to photon recycling and minimal radiation leakage in near-field operation, the PV cell used in near-field TPV systems can be much thinner compared to those used in solar PV systems. Since non-radiative recombination is a volumetric effect, use of a thinner cell reduces non-radiative losses per unit area. The combination of these two opportunities leads to increasingly large values of Voc as the TPV vacuum gap decreases. Hence, although operation in the near-field was previously perceived to be beneficial for electrical power density enhancement, here, we emphasize that thin-film near-field TPVs are also significantly advantageous in terms of Voc and consequently conversion efficiency as well as power density. We provide numerical results for an InAs-based thin-film TPV that exhibits efficiency > 50% at an emitter temperature as low as 1100 K.

The 2022 applied physics by pioneering women: a roadmap

“…Interestingly, nanophotonics and nanophonics converge in two respects: in the interaction between light and mechanical motion, which is at the core of optomechanics, and due to the fact that the nanophotonics of long wavelength radiation is at the verge of meeting nanophononics by engineering heat management [186], a field in which there are also theoretical and experimental critical challenges. Phonons, as quantized vibrations of the atomic lattice, are fully described by their phononic band structure or dispersion relation, ω(q), which provides a deep understanding of the material thermal properties, harmonic lattice dynamics, and the propagation of coherent waves.…”