Tunability of a broad-band selective metamaterial emitter in thermophotovoltaic systems

In a thermophotovoltaic (TPV) system, it is crucial to realize the excellent matching between the radiation spectrum of emitter and the photovoltaic cells, which will be helpful to improve the conversion efficiency and output power. We have focused on the study of tunability of a multi-layer metamaterial (MTM) selective emitter with the dielectric-metal pyramid structure to screen and optimize the material combinations and geometric parameters for matching GaSb and InGaAsSb cells. It is found that the selective metamaterial emitter composed of various material combinations can achieve the broadband emission, which is formed by overlapping of multiple resonance peaks at the region below the cutoff wavelength. The MTM emitters composed of W/Ta/Mo−BeO, W/Ta/Mo−SiO2, W/Mo−Si3N4, and W−HfO2, respectively, are characterized by the extraordinary emission spectrum for matching GaSb cells. We have selected the material combination of Ta−SiO2 with the excellent emission spectrum to obtain an excellent emission spectrum matching the bandgap of GaSb cells by optimizing the geometric parameters. The optimal geometric parameters of emitter composed of the material combination of Ta−SiO2 have been obtained. Moreover, the efficiency and output power of TPV system reaches 17.52% and 0.025 W/cm2 at 1000 K and even approaches 36.27% and 0.79 W/cm2 at 1500 K. It is indicated that the optimized emitter can achieve the near-perfect utilization of in-band photons and well suppress the sub-band loss. It can be also found that the MTM emitter composed of W−HfO2 exhibits an excellent matching degree with InGaAsSb cells. It is also demonstrated that the MTM emitter with pyramid structure has a good scalability for matching other available PV cells. The high conversion efficiency realized by materials screening and geometric optimization provides a potential pathway for the design of TPV emitter. •The emission spectrum of emitter was screened from multiple material combinations for matching GaSb and InGaAsSb cells.•The effect of geometric parameters on the emission spectrum of emitter has been investigated in detail.•The TPV efficiency with optimized emitter shows a great improvement compared with the papers using the same method.