Highly efficient sub-100-nm thermophotovoltaic cells enhanced by spectrally selective two-dimensional metasurface

Great efforts have been devoted to the investigation of selective emitters and filters for improving the conversion efficiency of thermophotovoltaic (TPV) systems. This work proposes a spectrally selective ultrathin cell with two-dimensional (2-D) metasurface for high-efficiency TPV energy conversion. The cell is composed of Ag substrate, ultrathin gallium antimonide (GaSb) photovoltaic layer, and 2-D metasurface comprising symmetric 2-D metallic grating. The spectral-normal absorptance of the proposed structure is calculated by the finite-element method and the results show significant enhancement in the photon absorption comparing to the free-standing GaSb layer with the same thickness, which is attributed to the excitation of magnetic polariton and Fabry-Perot resonance. The effects of using indium tin oxide and graphene as front electrodes on the absorptance of the proposed ultrathin cell are investigated. The TPV system efficiency is also evaluated using the proposed ultrathin cell. The results show that the TPV efficiency with the proposed ultrathin cell can approach 29.1% with a black emitter at 1500 K and can be further increased to be 35.1% using an ideal selective emitter. This work will facilitate the development of next-generation high-efficiency TPV systems.