(July 31, 2015) A
team headed by Prof. Silke Christiansen has developed a transparent electrode
with high electrical conductivity for solar cells and other optoelectronic
components – that uses minimal amounts of material. It consists of a random
network of silver nanowires that is coated with aluminium-doped zinc oxide. The
novel electrode requires about 70 times less silver than conventional silver
grid electrodes, but possesses comparable electrical conductivity.
The electrodes for connections on the “sunny side” of a
solar cell need to be not just electrically conductive, but transparent as
well. As a result, electrodes are currently made either by using thin strips of
silver in the form of a coarse-meshed grid squeegeed onto a surface, or by
applying a transparent layer of electrically conductive indium tin oxide (ITO)
compound. Neither of these are ideal solutions, however. This is because silver
is a precious metal and relatively expensive, and silver particles with
nanoscale dimensions oxidise particularly rapidly; meanwhile, indium is one of
the rarest elements on earth crust and probably will only continue to be
available for a few more years.
Mesh of silver
nanowires
Manuela Göbelt on the team of Prof. Silke Christiansen has
now developed an elegant new solution using only a fraction of the silver and
entirely devoid of indium to produce a technologically intriguing electrode.
The doctoral student initially made a suspension of silver nanowires in ethanol
using wet-chemistry techniques. She then transferred this suspension with a
pipette onto a substrate, in this case a silicon solar cell. As the solvent is
evaporated, the silver nanowires organise themselves into a loose mesh that
remains transparent, yet dense enough to form uninterrupted current paths.