Analysis of air-bridge thermophotovoltaic devices and systems

We present a model of air-bridge InGaAs and Si thermophotovoltaic (TPV) systems that guides the optimization of both output power density and efficiency, considering key design factors such as series resistance ( R s ), shunt resistance , out-of-band reflectance, and dissipated power. Assuming lossless emitter-to-cell coupling, an InGaAs TPV cell can reach an efficiency of 43.2 % and output power density ( P out ) = 1.6 W/cm 2 at an emitter temperature of T h = 1060 °C. At T h = 1500 °C, P out can exceed 9 W/cm 2 , although ohmic losses may reduce the efficiency to below 35 %. In contrast, Si air-bridge TPVs exhibit relatively high parasitic power losses due to free carrier absorption (FCA), limiting the efficiency to 30.1 % at T h = 1400 °C. By suppressing FCA, this efficiency can be improved to 40 %. However, the high R s of Si TPV cells restricts P out to <2 W/cm 2 , suggesting that Si-based TPV systems may not be suitable for high-power applications. While this model has been used for InGaAs and Si TPVs, its versatility allows for optimizing the performance of TPV systems with other semiconductor materials and device structures. • A general model comparing Si and III-V TPV cells is presented. • The model includes series and shunt resistances and recombination lifetime. • Si TPV cells exhibit lower efficiency III-V cells due to free carrier absorption. • The power density of Si TPV cells is limited to 2 W/cm 2 from series resistance.