Resonant Thermal Emitters and PV Cells for Thermophotovoltaic Power Generation

A thermophotovoltaic (TPV) power generation system based on resonator-pixel (RP) emitters and photovoltaic (PV) cells is proposed. The RP structure enables wavelength-selective emission and absorption, which increases the system power throughout and efficiency. An RP structure contains a thin semiconductor material etched into an array of micron-sized rings and covered with a metal layer. The emissivity of the RP emitter is determined by equating it to absorptivity and is modeled by three-dimensional electromagnetic modeling. The result shows that the emitter is able to increase the wavelength selectivity by eight times compared to a bulk emitter. Integrated with an RP PV cell having enhanced absorption at the band edge, the power conversion efficiency can be maintained constant in a wide range of temperatures, while the power throughput increases by 1.7 times. In addition, the RP emission is highly directional. Its far-field beamwidth is less than 10°, with which the emitter and PV cell can be placed at a larger distance to avoid convectional heating on the PV cell. In this work, we also confirm a near-field TPV effect that raises the electrical power by a factor of 2 when the emitter and cell are placed less than 2 μ m apart.