Design and Fabrication of Grating-Based Filters for Micro-thermophotovoltaic Systems

Abstract

Micro-thermophotovoltaic systems are an appealing alternative as portable power generators with high energy density and longevity. Recent advances in the nanofabrication have enabled the design of spectrally selective thermal emitters matched to the low bandgap PV cells. Here, we propose a one-dimensional amorphous silicon grating-based structure on quartz substrate as selective filter. The simulations are performed to optimize the grating parameters to minimize the transmission of below bandgap photons for GaSb PV cell (cut-off wavelength of 1.8 μm). The fabrication of the optimized design is carried out using interference lithography. The fabricated grating parameters are grating period (2.49 μm), duty cycle (39–41%), and grating thickness (520  30 nm). The fabricated filter is characterized using an optical setup and the obtained transmission spectrum when convoluted with blackbody spectrum at 1500 K showed that 71.17% of above bandgap photons are transmitted and only 24.3% of below bandgap photons are transmitted. Therefore, approximately 75% of the below bandgap photons are reflected by filter which provides the advantage of reduction in heat loss and enhancement of the combustion which contributes to the overall increase in TPV system efficiency.