Optimizing III-V thermophotovoltaic bandgaps for cost-effective thermal energy conversion

This study combines static performance metrics with dynamic energy-yield calculations and shows that techno-economic viability is governed not only by conversion efficiency but also by the total energy generated. An electro-thermal framework is used to evaluate static operation for waste heat recovery and dynamic operation for thermal energy storage across III-V thermophotovoltaic cells with bandgaps ranging from 0.74 eV (InGaAs) to 1.42 eV (GaAs), accounting for parasitic optical and resistive losses. While bandgaps in the 0.9–1.1 eV range exhibit optimal conversion efficiency near 42 %, 1.42-eV GaAs achieves the highest power output – up to 10 W/cm² – with a marginal efficiency penalty of less than 2 percentage points. In the techno-economic assessment for waste heat recovery, 0.74-eV InGaAs emerges as a viable candidate for relatively low emitter temperatures below 1300 °C, offering a competitive levelized cost of electricity below $0.1/kWh. Meanwhile, InGaAsP alloys with bandgaps of 0.9–1.18 eV achieve a low levelized cost of electricity below $0.05/kWh, comparable to conventional solar photovoltaic systems. Conversely, for thermal energy storage, wider bandgaps become more advantageous; specifically, binary GaAs (1.42 eV) achieves a levelized cost of storage below $0.2/kWh, even at annual energy throughputs below 0.5 MWh/yr. Given the scalability of the system, GaAs holds significant potential for applications ranging from portable to grid-scale energy storage. Overall, this work provides a material-selection roadmap, highlighting that the transition from InGaAs/InGaAsP to binary GaAs is critical for reconciling the distinct requirements of continuous waste heat recovery and cost-effective energy storage technology.