| Description |
Thermophotovoltaic (TPV) power generators convert infrared photons from a terrestrial source into electricity and consist of a high-temperature radiator and a low bandgap photovoltaic (PV) cell separated by a vacuum gap. To potentially improve TPV performance, near-field TPV (NF-TPV) devices have been proposed, which capitalize on evanescent modes by separating the radiator and cell by a sub-wavelength vacuum gap. This thesis is organized into two main parts. The first part focuses on the design of an indium arsenide (InAs) PV cell for NF-TPV devices while the second part investigates a front contact grid with sub-wavelength dimensions. In the first part, an InAs cell is designed for use in a NF-TPV device consisting of macroscale surfaces separated by a sub-wavelength vacuum gap with a front contact grid for charge carrier extraction. The performance of the cell is modified by the presence of the front contact grid, consisting of metallic grid fingers and a busbar. It is assumed that the front contact grid does not scatter radiation significantly, and the widths of the grid fingers and their spacing are limited accordingly. The grid architecture must be optimized for the specific vacuum gap thickness at which the NF-TPV device operates and for the specific dimensions of a given device. For example, when the grid is optimized for a 1 × 1 mm2 device operating at a vacuum gap of 100 nm, the grid reduces the maximum power output by a factor of approximately 2.5, but the near-field enhancement is still a factor of approximately 21 over the far-field value. In the second part, the assumption that the grid does not scatter radiation significantly is relaxed, and a grid with fingers having widths and spacing less than the characteristic thermal wavelength is investigated. An alternative front contact architecture consisting of a gold grating that is 500 nm thick with a period of 100 nm and a filling ratio of 0.8 can eliminate the shadowing losses introduced by the front contact grid and reduce series resistance losses by 95% while maintaining an absorbed radiative flux in the cell that is 2.4 times larger than the blackbody limit. |
