Antireflection coated refractory metal matched emitters for use with GaSb thermophotovoltaic generators

GaSb thermophotovoltaic cells can be combined with infrared emitters to produce electric power. In this application, both power density and efficiency are important. High power density requires a practical target emitter temperature of 1600 K. In order to reach this temperature, spectral efficiency becomes extremely important. Radiation with wavelengths greater than 1.8 microns cannot be converted by the GaSb cells; instead, this long wavelength radiation overheats the cells, limiting power density and efficiency. A solution is to use refractory-metal coated emitters, because metals have low emittance at long wavelengths. Further, an antireflection (AR) coating on the metal can enhance the emittance in the cell convertible band. A spectral efficiency of 75% has been demonstrated for an AR coated tungsten emitter and a GaSb cell power density of 1.5 Watts/cm² has been measured with an AR coated tungsten emitter operating at 1555 K