Overcoming the black body limit in plasmonic and graphene near-field thermophotovoltaic systems

Abstract

Near-field thermophotovoltaic (TPV) systems with carefully tailored emitter-PV properties show large promise for a new temperature range (600 – 1200K) solid state energy conversion, where conventional thermoelectric (TE) devices cannot operate due to high temperatures and far-field TPV schemes suffer from low efficiency and power density. We present a detailed theoretical study of several different implementations of thermal emitters using plasmonic materials and graphene. We find that optimal improvements over the black body limit are achieved for low bandgap semiconductors and properly matched plasmonic frequencies. For a pure plasmonic emitter, theoretically predicted generated power density of 14 W/cm2 and efficiency of 36% can be achieved at 600K (hot-side), for 0.17eV bandgap (InSb). Developing insightful approximations, we argue that large plasmonic losses can, contrary to intuition, be helpful in enhancing the overall near-field transfer. We discuss and quantify the properties of an optimal near-field photovoltaic (PV) diode. In addition, we study plasmons in graphene and show that doping can be used to tune the plasmonic dispersion relation to match the PV cell bangap. In case of graphene, theoretically predicted generated power density of 6(120) W/cm2 and efficiency of 35(40)% can be achieved at 600(1200)K, for 0.17eV bandgap. With the ability to operate in intermediate temperature range, as well as high efficiency and power density, near-field TPV systems have the potential to complement conventional TE and TPV solid state heat-to-electricity conversion devices.

Nanoscale Radiative Heat Flow due to Surface Plasmons in Graphene and Doped Silicon

“…Optimization of TPV efficiency in NF however is difficult due to proximity effects [20]. Thus the RHT enhancing behavior of graphene [21][22][23][24][25][26] may play an important role there [21]. While previous experiments reported RHT enhancements due to phonon polaritons [4][5][6], to date no experiments have reported the effect of plasmons or ultra thin films on NF RHT, this is the aim of the present work.…”

“…In contrast in near field (NF) surface excitations such as phonon polaritons and low frequency plasmons result in an improved spatial coherence [16] and narrow bandwidths [8], leading to an increase in energy density beyond the Planck blackbody limit [1][2][3]. For materials such as SiC and SiO 2 the surface excitations are attributed to ion-vibrations [4,5], whereas for doped silicon [11] and graphene [10,21] they are due to electronic vibrations (plasmons). For these materials, the plasmon frequency can be tuned by changing the amount of free carriers.…”

“…The efficiency of NF RHT for silicon and graphene to other materials strongly depends on the plasmon frequency [10,11,21], which in turn depends on the amount of free carriers. For the samples used here the carrier density n h and mobilities μ were determined by Hall measurements ( fig.…”

Extraordinary Light-Induced Local Angular Momentum near Metallic Nanoparticles

“…if f f i i (13) Now the torque can be defined as the change of the molecular AM multiplied by the transition rate (1)…”

Enhanced energy transfer by near-field coupling of a nanostructured metamaterial with a graphene-covered plate

“…By covering graphene on doped silicon nanowires, which exhibit strong hyperbolic behaviors, Liu et al [31] theoretically demonstrated near-unity photon tunneling probability in a broad frequency range and k space by the coupling between graphene plasmon and hyperbolic modes. In terms of near-field radiative transport between dissimilar materials, Ilic et al [32] applied graphene on an emitter and showed that the near-field TPV system performance can be optimized by matching the graphene plasmon with the cell bandgap. Messina and Ben-Abdallah theoretically demonstrated improved near-field TPV efficiency between a hexagonal boron nitride (hBN) emitter and graphene-coated InSb cell by effective near-field coupling of hBN phonon modes with graphene plasmon [33].…”