Thermophotovoltaic Energy Conversion in Far-to-Near-Field Transition Regime

Abstract

Recent experimental studies on near-field thermophotovoltaic energy conversion have mainly focused on improvingperformance via photon tunneling of evanescent waves. In the sub-micron gap, however, there exist peculiar phenomena induced bythe interference of propagating waves, which are seldom observed in the full spectrum radiation due to the massive increase inevanescent modes. Here, we experimentally demonstrate the oscillatory nature of near-field thermophotovoltaic energy conversion inthe far-to-near-field transition regime (250-2600 nm), where evanescent and propagating modes are comparable due to the selectivespectral response by the photovoltaic cell. Noticeably, we show that the same amount of photocurrent can be generated at differentvacuum gaps of 870 and 322 nm, which is 10% larger than the far-field value.