High external quantum efficiency from double heterostructure layers as selective emitters in thermophotonic systems

One of the main disadvantages of thermophotovoltaics is the need for a highly perfect selective emitter or filter to achieve high conversion efficiency. Thermophotonics overcomes this through the use of a heated light emitting diode as an extremely selective emitter. To achieve net conversion of heat to electricity with thermophotonics, a LED with high external quantum efficiency is required. As the initial step to demonstrate this concept, an AlGaAs/GaAs double heterostructure was optically pumped with energy higher than bandgap at room temperature. An EQE of 80% was measured for a doped planar sample on a transparent substrate. To the authors' knowledge this is the highest EQE for a planar structure ever reported. The results for undoped samples agree well with independent thermal measurements and with simulation data from our photon ray-tracing model. The low surface recombination velocity implies that the sample quality is excellent.