Involving
a single-step, low-cost, Ag-assisted chemical etching
process at ambient temperature, vertically aligned uniform silicon
nanowire (Si-NW) arrays are produced with various lengths following
an identical etching rate. The formation mechanism of Si-NW arrays
by the selective etching of bulk c-Si via a continuous reduction–oxidation-dissolution
process is proposed, involving the conjoint roles of Ag-NPs and Ag-dendrite
structures. Each Ag0 deposit on the Si surface acts like
a nanoelectrochemical cell, wherein both the cathode and anode reactions
proceed simultaneously. Significantly low reflectance of <1% over
a wide spectral range via the inherent light-trapping capabilities
makes the Si-NW arrays a unique semiconductor for fabricating solar
cells with embedded self-generated antireflection. The multilayer p-type amorphous-Si/intrinsic amorphous-Si/n-type crystalline-Si NW (p-a-Si/i-a-Si/n-c-Si-NW) heterojunction solar cell fabricated
in core–shell configuration, with a ∼1.9 μm long
NW-arrays core generated via chemical etching of the n-type (100) Si wafer and the shell-layers grown by plasma CVD, delivers
the highest PV conversion efficiency of η ∼ 5.64%. A
substantial charge recombination loss due to a significant lattice
mismatch at the i-a-Si/n-c-Si-NW
heterojunction has been minimized further by introducing an intrinsic
nanocrystalline-Si (i-nc-Si) layer at the interface.
The Si-NW solar cell comprising its p-a-Si/(i-a-Si/i-nc-Si)/n-c-Si-NW
modified core–shell structure demonstrates an increased J
SC ∼ 29 mA cm–2, improved
FF ∼ 50%, and elevated PV conversion efficiency of η
∼ 7.54%, which is significant of its type, following the spirit
of the present pursuit of a simple low-temperature solar cell fabrication
route.