Physical and numerical investigation of single-layered tungsten gratings for thermophotovoltaic emitters

A polarization-insensitive thermophotovoltaic emitter which is easily manufactured using microfabrication techniques is optimized based on physical and numerical studies. First, ranges of geometrical dimensions of the emitter based a single-layered tungsten grating are confined with the excitation of surface plasmon polaritons, cavity resonance, and Wood´s anomaly at defined wavelengths. Then, a combined numerical scheme including the rigorous coupled-wave analysis and a genetic algorithm is implemented to find the grating´s geometry with an objective of maximizing emittance. The results show that the optimized emitter yields the peak emittance of 0.997 and 0.935 at the transverse electric and transverse magnetic polarizations, respectively. The physical mechanism of the enhanced emittance is also confirmed by patterns of electromagnetic fields and Poynting vectors using the finite difference time-domain method. Overall, the results presented in this study show that the single-layered grating provides a very simple and ideal solution for thermophotovoltaic applications.