Select An Issue
Selected Issue:
Issue 4
22nd
February 2010
C&I Magazine
New flat lighting panels fabricated from graphene
Andrew Turley,
22/02/2010
Graphene – single atom thick sheets
of carbon – is the key to entirely
organic lighting devices that are
both cheap to make and easy to
recycle, scientists say. The work
could lead to plastic panels that
would produce light evenly across
large areas of walls and ceilings.
Organic light-emitting diodes
(OLEDs) are made from conductive
polymers that release photons when
holes combine with electrons from
an electrical current. Compared
with liquid crystal display screens,
OLEDs offer thinner units, better
picture quality and greater energy
efficiency in TVs, computers and
mobile phones.
But OLEDs remain expensive to
make and difficult to recycle due
to the rare metal indium tin oxide
electrode.
The group of Swedish and US
researchers has made a light-emitting
electrochemical cell (LEC) with a
graphene cathode and an anode of
conductive organic dyes (ACS Nano
doi: 10.1021/nn9018569). LECs are
structurally similar to OLEDs,
but use a conductive gel of
light-emitting polymers
in a liquid electrolyte,
rather than a solid polymer
matrix. The graphene LECs
produced similar light
intensity, at similar levels
of energy comsumption, to
polymer OLEDs, says coauthor
Nathaniel Robinson
from Linköping University in
Sweden.
But they could be much
cheaper for two reasons.
First, graphene is cheaper
than indium tin oxide.
Second, they can be made
from solutions and are relatively
insensitive to variations in thickness,
which means large-scale production
could be based on efficient ‘roll-toroll’
printing processes.
LECs are unlikely to replace
OLEDs in display screens with
rapidly moving images, because of
the time it takes to turn them on.
‘The LEC has mobile ions,’ Robinson
explains. ‘These ions have to move
around a bit when you turn it on,
so it can take a tenth of a second.
You’re not going to make a TV out
of LECs.’
But they would lend themselves
to light panels that could be rolled
out on large areas of walls or
ceilings like wallpaper, rather than
point sources which, because of the
extreme heat generated, would melt
organic materials. But that could
inspire all new lighting strategies.
‘The architects love these ideas,’
Robinson says.
Robinson has filed patents
and set up a company to take the
technology to market.