TCAD simulations of a barrier structure designed to improve the performance of very-low bandgap InAs/InAsSb thermophotovoltaic cells

Very-low bandgap TPV cells (<0.4 eV) usually require cryogenic cooling (∼ 70 K) because of their high intrinsic dark current densities. To mitigate this effect, a barrier structure combined with a gallium-free InAs/InAsSb absorber, inspired by infrared photodetectors, is studied through optoelectronic TCAD simulations. This analysis reveals that the power output of the cell could be increased by 24% at 200 K thanks to this design, when compared to an equivalent PIN structure. The quantitative effects of contact doping, parasitic absorption, and carrier diffusion length are discussed in detail. An optimum design is extracted, predicting a power output of 0.3 W/cm² and pairwise efficiency of 16% at 200 K under the illumination of an 800^∘C black-body emitter. The physical mechanisms limiting the performance of the cell at higher temperatures are identified, and a guideline for future improvements is proposed.