Pareto Optimal Spectrally Selective Emitters for Thermophotovoltaics via Weak Absorber Critical Coupling

Abstract

Tailoring the emission spectra of a thermophotovoltaic emitter away from that of a blackbody has the potential to minimize transmission and thermalization loss in a photovoltaic receiver.Selective thermophotovoltaic emitters could lead to solar energy conversion with efficiency greater than the Shockley-Queisser limit and could facilitate the generation of useful energy from waste heat. We introduce a new design to radically tune thermal emission that leverages the interplay between two resonant phenomena in simple planar nanostructures -absorption in weakly-absorbing nanofilms and reflection in multi-layer dielectric stacks. We employ a virtual screening approach to identify promising structures for a selective thermal emitter from a search space of millions, several of which approach the ideal values of a step-function selective thermal emitter. One of these structures is experimentally fabricated and evaluated, which includes a weakly-absorbing alloy with tailored optical properties fabricated by atomic layer deposition. The versatility of the design and fabrication approach result in an emitter with excellent spectral density (0.8 W/cm 2 sr) and spectral efficiency (46.8%) at 1373 K. Future experimental challenges to a more accurate realization of the optimal structures calculated are also considered, including a weak absorber with more ideal optical constants and even greater thermal stability.

Accelerating the discovery of multilayer nanostructures with analytic differentiation of the transfer matrix equations

“…(17); (ii) compute the gradients of the reflectivity and transmissivity amplitudes via Eqs. (14) and (15), and the gradients of the reflectivity and transmissivity via Eqs. (10) and (11);…”

“…Designing materials on the nanoscale can have a profound impact on how optical energy flows through those materials, which can in turn dramatically improve the performance of nanostructured materials for energy-related applications including solar and (solar) thermophotovoltaic energy conversion [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17], radiative cooling [18][19][20][21][22][23], incandescent lighting [24][25][26][27], among others. Multilayer planar nanomaterials, stacks of flat materials with nanoscale thickness, have emerged as promising candidates for such applications because they present highly tunable optical and thermal emission properties and are relatively easy to fabricate.…”

Energy Applications of Magnetocaloric Materials

“…Over the last 20 years, in addition to thermoelectricity, much research on solid‐state thermal energy harvesting ( Figure 2 ) has also focused on thermionics and thermophotovoltaics . Researchers have also investigated new frontiers in spin‐caloritronics, spin‐Seebeck, and anomalous Nernst effects .…”

“…[82,84] Over the last 20 years, in addition to thermoelectricity, much research on solid-state thermal energy harvesting (Figure 2) has also focused on thermionics [85][86][87] and thermophotovoltaics. [88][89][90] Researchers have also investigated new frontiers in spin-caloritronics, [91,92] spin-Seebeck, [93,94] and anomalous Nernst effects. [95,96] However, with the rapid development of caloric (ferroic) materials and technologies for refrigeration and air conditioning, caloric (ferroic) power generation [64,77] is being revisited and prototype devices are being developed.…”

Narrow‐Band Thermal Emitter with Titanium Nitride Thin Film Demonstrating High Temperature Stability

“…Infrared (IR) selective thermal emissions can improve the conversion efficiency of heat energy converting to photon energy 1,2. IR thermal emitters have potential applications such as nondispersive IR gas sensing,3 photodetectors via high hot‐electron generation,4–6 radiative cooling,7 and thermophotovoltaics (TPVs) 8. When selective thermal emitters are intended to emit in shorter mid IR range (e.g., an emitter for TPV system), the emitter has to be heated above one thousand kelvin 9.…”