Optical characteristics of one-dimensional Si∕SiO2 photonic crystals for thermophotovoltaic applications

Abstract

This article presents a detailed exploration of the optical characteristics of various one-dimensional photonic crystal structures designed for use as a means of improving the efficiency and power density of thermophotovoltaic (TPV) devices. The crystals being investigated have a ten-layer quarter-wave periodic structure, and are based on $\mathrm{Si}∕\mathrm{Si}{\mathrm{O}}_2$ and $\mathrm{Si}∕\mathrm{Si}\mathrm{O}\mathrm{N}$ material systems. For TPV applications the crystals are designed to act as filters, transmitting photons with wavelengths below $1.78\mu \mathrm{m}$ to a GaSb photodiode, while reflecting photons of longer wavelengths back to the source of thermal radiation. In the case of the $\mathrm{Si}∕\mathrm{Si}{\mathrm{O}}_2$ structure, the Si and $\mathrm{Si}{\mathrm{O}}_2$ layers were designed to be 170 and $390\mathrm{nm}$ thick, respectively. This structure was fabricated using low-pressure chemical vapor deposition. Reflectance and transmittance measurements of the fabricated $\mathrm{Si}∕\mathrm{Si}{\mathrm{O}}_2$ photonic crystals were taken from $0.8\text{to}3.3\mu \mathrm{m}$ for both polarizations and for a range of incident angles. Measurement results were found to correlate well with simulation results for the ideal structure. Measurement results were used to predict the TPV system efficiency, power density and spectral efficiency using an ideal thermodynamic model of a TPV system.