Comparison of optimized GeSn/Si heterojunction and GaInAsSb/GaSb thermophotovoltaic cells with similar bandgaps

Abstract

The bandgap of Ge1−xSnx material can be designed within 0.5 ∼ 0.6 eV with different Sn content, and the characteristic of indirect bandgap of pure Ge will change to direct, which make Ge1−xSnx become a proper and low cost thermophotovoltaic cell material. Here we investigate direct bandgap Ge1−xSnx cells with bandgaps of 0.508 ∼ 0.548 eV. Triple antireflection layers, the surface recombination rate, p–n junction depth, impurity doping concentration, etc are optimized for cell design. The optimal cell structures are adopted for cell performance evaluation under given blackbody radiation within 1000 ∼ 2000 K. Simultaneously, the output power densities of GeSn cells are compared with those of traditional GaInAsSb cells with similar bandgap designs. GeSn cells show comparable performances with GaInAsSb cells over the temperature range of 1000 ∼ 1500 K blackbody radiation, and the efficiencies are 1.01 ∼ 2.49 times over 1500 ∼ 2000 K.