Electrical and optical performance characteristics of p/n InGaAs monolithic interconnected modules [thermophotovoltaics]

There has been a traditional trade-off in thermophotovoltaic (TPV) energy conversion development between system efficiency and power density. This tradeoff originates from the use of front surface spectral controls such as selective emitters and various types of filters. A monolithic interconnected module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual indium gallium arsenide (InGaAs) devices series-connected on a single semi-insulating indium phosphide (InP) substrate. The MIMs are exposed to the entire emitter output, thereby maximizing output power density. An infrared (IR) reflector placed on the rear surface of the substrate returns the unused portion of the emitter output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Initial MIM development has focused on a 1 cm² device consisting of eight (8) series interconnected cells. MIM devices, produced from 0.74 eV InGaAs, have demonstrated V_oc=3.2 volts, J_sc=70 mA/cm² and a fill factor of 66% under flashlamp testing. Reflectance measurements (>2 μm) of these devices indicate a reflectivity of >82%. MIM devices produced from 0.55 eV InGaAs have also been demonstrated. Addition, conventional p/n InGaAs devices with record efficiencies (11.7% AMO) have been demonstrated