Towards High-Efficiency Triple-Junction Bifacial III-V Nanowire-on-Silicon Solar Cells: Design Approaches Enabling the Concept

Using rigorous coupled wave analysis (RCWA) for simulating absorption in GaAs
_0.73
P
_0.27
and In
_0.81
Ga
_0.19
As nanowire (NW) arrays grown on 200 μm-thick active silicon substrate, geometrical parameters of the arrays corresponding to maximum broad-band absorption were established. Conditions for current matching between the NW and Si sub-cells were designed by optimizing the NW diameter (D
_top
= 350 nm, D
_bot
= 700 nm) and center-to-center distance (P
_top
= 500 nm, P
_bot
= 1000 nm), as well as making use of the waveguide properties of NWs and back surface reflectors.