Photon tunneling mechanism and performance analysis of near-field thermophotovoltaic system with plasmonic emitter

Performance of thermophotovoltaic (TPV) system can be significantly improved by incorporating photon tunneling. In the near-field thermophotovoltaic system (NF-TPV) containing plasmonic emitter, where surface plasmon polaritons (SPPs) excited at the vacuum-plasmonic emitter interface may couple with total internal reflection (TR) mode to result in the TR-SPPs mode, or other electromagnetic modes. In this work, we investigate the photon tunneling mechanism and its impact on the performance of NF-TPV system with plasmonic emitter. Analytical formula of the dispersion relation of the TR-SPPs mode is derived. The mechanism of self-coupled SPPs mode is clarified. These mechanisms undergo transitions at different separation distances. As the distance decreases, TR-SPPs mode is suppressed, while the self-coupled SPPs mode progressively assumes a dominant role, which significantly enhances the spectral radiative heat flux surpassing the bandgap. The spectral changes increase the power density as the distance decreases. Especially, the efficiency can be significantly improved when NFRHT is primarily mediated by the self-coupled SPPs mode. These findings enhance the comprehension of photon tunneling mechanism and provide guidance for NF-TPV system design and optimization.