High Operating Temperature, Radiation-Hard MIM Thermophotovoltaic Converters

Spire Corporation is developing a key component for thermophotovoltaic (TPV) power technology for deep space missions. We are developing InGaAs monolithically interconnected modules (MIMs) that convert thermal photons from the ~1100C General Purpose Heat Source (GPHS) into electrical power. The innovation is that these MIMs are designed to operate at higher cell temperatures (150C) and be more radiation-hard than current MIMs to better match the cell environment on missions. In Phase 1, we developed a model that predicts an optimum InGaAs bandgap (adjustable during epigrowth) for the operating temperature and 1100C blackbody GPHS spectrum of ~0.7eV, made sample devices, and tested temperature coefficients to confirm the model and measured data agree (e.g. model predicts –1.7mV/C for Voc vs. –1.8mV/C for data). In Phase 2, we will perform five iterations of a model, design, epitaxially grow, process, and test cycle. Data from each cycle will be used to improve the next design. Testing will include both radiation, temperature stability and accelerated life testing. Before program completion, we will survey NASA and commercial space power contractors for needs and make samples of the best design to distribute among space power contractors as a step toward generating interest and commercial sales.