[en] Nano-gap thermophotovoltaic energy converters have the potential to be excellent generators of electrical power due to the near-field radiative effect which enhances the transfer of energy from one medium to another. However, there is still much to learn about this new form of energy converter. This paper seeks to investigate three parameters that affect the performance of nano-gap thermophotovoltaic devices: the emitter material, the thermophotovoltaic cell material, and the cell thickness. Furthermore, the temperature profiles in insulated thin films (cells exposed to below-band gap near-field radiation) are analysed. It was discovered that an effective emitter material is one that has a high generalised emissivity value and is also able to couple with the TPV cell material through surface polaritons while a cell material's electrical properties and its thickness has heavy bearing on its internal quantum efficiency. In regards to the temperature profile, the heat-flux absorbed causes a rise in temperature across the thin film, but is insufficient to generate a temperature gradient across the film. - Highlights: • The effect of emitter and cell material on nano-gap TPV devices is investigated. • The effect of cell thickness on nano-gap TPV devices is investigated. • Nano-gap TPV cell's IQE is mostly determined by its electrical properties. • Decreasing cell thickness will increase IQE up to a maximum point. • A constant temperature rise can be assumed for sufficiently thin TPV cells.