Medium-Bridge Near-Field Thermophotovoltaic System

The energy conversion performance of thermophotovoltaic (TPV) systems can be improved when the vacuum gap between the emitter and the TPV cell is at the near-field owing to the photon tunneling of evanescent waves. Among them, the back-gapped-reflector TPV systems have gained interest as a method of improving their conversion efficiency by optimizing the spectral absorption of TPV cells. In this work, we introduce an alternative concept for the back-gapped-reflector TPV systems, namely the medium-bridge near-field TPV system, by building a medium bridge between the metal reflector and the TPV cell using SU8 nanofilm. The SU8 medium-bridge achieves a noticeable improvement in output performance by increasing the spectral absorption of the InAs cell and reducing parasitic absorption losses of the Au substrate. The results indicate that, as a consequence of the improved effect of the medium-bridge, the output power density and efficiency of this system exceed those of the conventional TPV system (which lacks a medium-bridge) by 26.4% and 36.5%, respectively. Moreover, we systematically analyze the modulation of medium-bridge thicknesses and cell thickness on output performance and clarify how both affect energy losses of this near-field TPV system. Our work offers a strategy to improve the energy conversion performance of the near-field TPV system, opening new opportunities for developing near-field energy conversion.