Design of emitter structures based on resonant perfect absorption for thermophotovoltaic applications

Abstract

We report a class of thermophotovoltaic emitter structures built upon planar films that support resonant modes, known as perfectly-absorbing modes, that facilitate an exceptional optical response for selective emission. These planar structures have several key advantages over previously-proposed designs for TPV applications: they are simple to fabricate, are stable across a range of temperatures and conditions, and are capable of achieving some of the highest spectral efficiencies reported of any class of emitter structure. Utilization of these emitters leads to exceptionally high device efficiencies under low operating temperature conditions, which should open new opportunities for waste heat management. We present a theoretical framework for understanding this performance, and show that this framework can be leveraged as a search algorithm for promising candidate structures. In addition to providing an efficient theoretical methodology for identifying high-performance emitter structures, our methodology provides new insight into underlying design principles and should pave way for future design of structures that are simple to fabricate, temperature stable, and possess exceptional optical properties.

Pt/Alumina Hyperbolic Metafilms with High‐Temperature Stability, Wide Wavelength Tunability, and Omnidirectional Absorption

“…These results indicate that the oxidation of Pt or interdiffusion of Pt into alumina did not occur during the heating test. The cross‐sectional TEM images, FFT diffraction patterns, and elemental mapping results demonstrated pristine Pt/alumina interfaces, supporting the superior thermal stability of our developed Pt/alumina hyperbolic metafilms to other thermal emitters using W or Ta …”

“…For a more quantitative comparison, we defined the average absorptivity for each sample, as shown in the insets of Figure c. Although the average absorptivity monotonically decreased with increasing θ, the difference was marginal; the average absorptivity at θ = 70° was merely 15% smaller than the maximum value at θ = 0°, outperforming any previously reported thermal emitters . Such broadband angular absorption was strongly supported by the transfer matrix method simulation, as shown in Figure d.…”

“…Preparing stable high‐temperature light absorbers is crucial for the implementation of radiation‐based energy applications, which are represented by solar steamers, thermal emitters in thermophotovoltaics, and infrared incandescent lamps . Tungsten (W) and tantalum (Ta) are the most common refractory metals with a melting temperature exceeding 2000 K, and thus can preserve their absorption (or radiation) spectra at high temperatures.…”

“…Due to the isotropic distribution of thermal radiation, maintaining a large absorption over a wide range of incident angles is also an important design consideration to achieve high‐efficiency thermal emitters. To fulfill these optical requirements, refractory metals are sandwiched by other dielectrics or structured at the wavelength scale, as in one‐dimensional (1D) multilayer films, two‐dimensional (2D) surface reliefs, or three‐dimensional (3D) self‐assembled structures . Therefore, a careful study of metal/dielectric interfaces is needed to advance the development of radiation‐engineered devices, otherwise these devices could not reliably operate at high temperatures due to thermal problems, including surface oxidation and structural deformation.…”

WPTherml: A Python Package for the Design of Materials for Harnessing Heat

“…to support optical resonances known as surface plasmon polaritons [13][14][15], and perfectly absorbing modes [16][17][18]. We have included the capability to analyze multilayer structures for both surface plasmon polariton and perfectly absorbing modes through the find_spp() and find_pa() methods of the multilayer class, respectively.…”