Silicon-based metamaterial selective emitter for thermophotovoltaic applications

In this work, we present the design and optimization of a silicon-based selective emitter (SE) for thermophotovoltaic (TPV) systems with enhanced spectral efficiency. The proposed SE combines a broadband infrared absorber, a periodic triangular arrays of heavily doped silicon in this case, and a one-dimensional (1D) dielectric photonic crystal filter alternating silicon and silicon dioxide (Si/SiO2) layers. Both parts are integrated within a single monolithic structure that forms the selective emitter. The broadband absorber ensures high emissivity in the in-band region (i.e., for wavelengths shorter than the bandgap wavelength of the TPV cell), while the photonic crystal filter selectively suppresses long-wavelength emission in the out-of-band region (i.e., for wavelengths longer than the bandgap wavelength of the TPV cell), resulting in a spectrally selective emission profile over a wide infrared range up to 8 μm. To enhance the performance of the structure, a Particle Swarm Optimization algorithm was implemented to optimize the thicknesses of the Si/SiO2 multilayers. The optimized design demonstrates a spectral efficiency improvement exceeding 20% compared to conventional quarter-wave photonic crystal structures, and more than 45% relative to a blackbody emitter at an operating temperature of 1500 K. Beyond the specific structure investigated in this study, the proposed optimization framework provides a general and flexible methodology that can be readily extended to other broadband emitters and tailored to different TPV cell bandgaps.