RESUMO
Hydrogenated amorphous silicon (a-Si:H)-based infrared photodiodes were fabricated by coating a-Si:H thin-film p-i-n layers over hydrothermally-synthesized disordered zinc oxide (ZnO) nanowire (NW) networks. Due to enhanced light scattering, the reversed biased three dimensional (3-D) radial-junction NW diodes showed an â¼10× increase in photocurrent under a broad spectrum (800-2000 nm) infrared (IR) illumination compared to planar devices. The diodes were optimized by using InGaZnO (IGZO) transparent top contacts that had 20% higher optical transmission in the IR compared to Al-doped ZnO electrodes. Reverse-bias dark current was minimized by optimizing the area of the NW sidewalls and the a-Si:H shell layer thickness. The former reduces the effects of carrier recombination along the NW core-shell interface and the latter minimizes the tunnelling current across the radial-junction device. An enhancement of â¼100× was achieved for these devices compared to non-optimized diodes.
RESUMO
The optics of core / shell nanowire solar cells was investigated. The optical wave propagation was studied by finite difference time domain simulations using realistic interface morphologies. The interface morphologies were determined by a 3D surface coverage algorithm, which provides a realistic film formation of amorphous silicon films on zinc oxide nanowire arrays. The influence of the nanowire dimensions on the interface morphology and light trapping was investigated and optimal dimensions of the zinc oxide nanowire were derived.
