Quaternary InGaAsSb thermophotovoltaic diodes

In-x Ga1-x As-y Sb1-y thermophotovoltaic (TPV) diodes were grown lattice matched to GaSb substrates by metal-organic vapor phase epitaxy in the bandgap range of E-G = 0.5 to 0.6 eV. InGaAsSb TPV diodes, utilizing front-surface spectral control filters, are measured with thermal-to-electric conversion efficiency and power density (PD) of eta(TPV) = 19.7% and PD = 0.58 W/cm(2), respectively, for a radiator temperature of T-radiator = 950 degrees C, diode temperature of T-diode = 27 degrees C, and diode bandgap of E-G = 0.53 eV.,Practical limits to TPV energy conversion efficiency are established using measured recombination coefficients and optical properties of front surface spectral control filters which for 0.53-eV InGaAsSb TPV energy conversion are eta(TPV) = 28% and PD = 0.85 W/cm(2) at the above operating temperatures. The most severe performance limits are imposed by 1) diode open-circuit voltage (V-OC) limits due to intrinsic Auger recombination and 2) parasitic photon absorption in the inactive regions of the module. Experimentally, the diode V-OC is 15 % below the practical limit imposed by intrinsic Auger recombination processes. Analysis of InGaAsSb diode electrical performance versus diode architecture indicates that V-OC and thus efficiency are limited by extrinsic recombination processes such as through bulk defects.