Energy-band-matched infrared emitter for use with low bandgap

Abstract

A thermophotovoltaic generator includes an infrared cobalt oxide doped refractory ceramic emitter having a broad power band region which is matched with the energy conversion band of a low bandgap thermophotovoltaic cell receiver. The generator is provided with a heat source or is constructed for mounting on a heat source or for holding a heat source, such as a radioisotope. The generator is compatible with any heat source, including, but not limited to, a hydrocarbon flame, nuclear reactors, and radioisotopes. The emitter is made of a refractory ceramic material such as cobalt oxide doped alumina or magnesia. The refractory compound of the emitter is preferably doped with a small number of substitutional ions to create a material for emitting near blackbody radiation in a wide wavelength band above a threshold energy level and a minimal amount of radiation at wavelengths longer than the threshold level. In preferred embodiments of the present invention, the cobalt oxide doped emitter strongly emits infrared radiation in a wavelength interval between about 1 and 2.1 microns. The photovoltaic cells of the receiver are preferably of Ge cells, GaSb cells, In(1-z)Ga(z)As cells and Ga(1-x)In(x)Sb(1-y)As(y), where x and y range between 0 and 0.2 and z ranges between 0.3 and 0.7. A silica heat shield may be positioned between the emitter and the receiver when combustion heat sources are used for confining the combustion byproduct gases.