Two-dimensional photonic crystals as selective emitters for thermophotovoltaic power conversion applications

Abstract

This research investigates the use of two-dimensional (2D) photonic crystals (PhC) as selective emitters and means of achieving higher efficiencies in combustion-driven thermophotovoltaic (TPV) systems intended as auxiliary power systems in automobiles. A TPV power conversion system functions on the principle of direct conversion of thermal radiation into electricity. A basic TPV system consists of an emitter and a photovoltaic (PV) diode. The emitter is heated and radiates photons of various energies. The PV diode captures the incident photons whose energy is equal to or greater than the band-gap energy of the PV diode. Ideally, all captured photons are converted into electricity. This thesis develops the fabrication process for a high-efficiency selective emitter. The radiation spectrum of this structure is closely matched to the sensitivity spectrum of the PV diode. The selective emitter is a 1[mu]m-period 2D PhC in tungsten consisting of 0.8/[mu]m holes in a square lattice. The background of selective radiation and structure selection process are presented in this text. The preliminary structures are fabricated using Lloyd's mirror laser interferometer and developed using reactive ion etching. The detailed parameters of preparation, exposure, soft- and hard-mask etching are presented. The physical analysis results are reported and compared to the expected structure.

(cont.) The final structure dimension match the initial specifications to within 5%.