Mid-Infrared Thermal Radiation Harvesting Using Uncooled Narrow Bandgap GeSn Thermophotovoltaic Cell

Abstract Thermophotovoltaic (TPV) cells are increasingly attractive for applications in industrial waste heat harvesting, aerospace energy management, and compact power generation. Deploying midwave-infrared (MWIR) TPV in practical applications requires narrow-bandgap semiconductors that not only absorb low-energy photons but also integrate with scalable, low-cost platforms. Although high-performance TPV devices have been demonstrated using III–V materials such as InAs, GaSb, and InGaAs(P), their use remains limited by cost and substrate size. With this perspective, narrow bandgap GeSn alloys are a promising alternative that extend group-IV absorption into the MWIR while being silicon-compatible. Although the potential of GeSn TPV cells has been predicted, no experimental demonstration has been reported. Here, proof-of-concept Ge0.91Sn0.09 p-i-n TPV diodes (1 mm diameter) grown on silicon were fabricated and their performance was benchmarked against commercial InAs and extended-InGaAs devices. Measurements at 300 K under 2.33 μm laser and ∼1445 K SiC Globar illumination revealed peak zero-bias responsivity of ∼0.17 A/W at ∼1.7 μm, and an output power of ∼0.41 mW/cm2. These devices show trends comparable to those of the InAs diode under identical conditions, although at reduced absolute levels. To assess the intrinsic performance potential of the experimentally realized GeSn p-i-n heterostructure, Poisson-drift-diffusion modeling incorporating experimentally calibrated emitter emissivity predicts power densities up to ∼40 mW/cm2 under moderate MWIR thermal illumination, indicating that the present devices operate far below their fundamental limits and are primarily constrained by defect-assisted recombination and transport losses. These results establish the feasibility of GeSn-based thermophotovoltaic operation and provide a foundation for future silicon-compatible TPV development.