Limiting Efficiencies Of Tandem Solar Cells Consisting Of Iii-V Nanowire Arrays On Silicon

We carry out a systematic study of tandem solar cells consisting of III-V nanowire arrays on silicon using electromagnetic simulations and device simulations. For four III-V materials, we use optical simulations and detailed balance analysis to optimize the nanowires' structural parameters to maximize the detailed balance efficiency. The results show different trends for materials with band gaps smaller and larger than optimal, due to the different requirements for achieving current matching. A higher than 30% detailed-balance efficiency can be achieved by using 1 mu m-tall nanowire arrays with optimal parameters. Sample device simulations are conducted to compare different junction geometries and surface conditions. We find that radial junctions are more robust to the presence of surface recombination. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4754317]