New research shows that |
In
the August issue of Nature Communications, Professor Ludvig Edman and
PhD Andreas Sandström at Umeå University, report that they have produced
organic light-emitting electrochemical cells (LECs) using a
roll-to-roll compatible process under ambient conditions.
“LECs
can thus be produced as inexpensive and large-area extremely thin
light-emitting devices for informative displays and, at a later stage,
lighting applications”, says Ludvig Edman, Professor in Physics.
Professor
Edman’s group at Umeå University is focusing on novel organic compounds
(such as light-emitting and conducting polymers and graphene) and
develops LECs based on such materials. The researchers have dramatically
improved the energy efficiency and lifetime of LECs, as well as
demonstrated the unique physics and chemistry behind their operation and
have recently enhanced the performance of LECs to a point where
lifetime and efficiency make LECs useful for signage applications.
The
next step in the development was to ensure that the manufacturing costs
can be attractive for commercial applications. The report shows that
using solely air-stable materials in a roll-coater apparatus, the team
managed to deposit a light-emitting layer and a PEDOT-PSS anode on top
of a flexible cathode-coated substrate mounted on a roll by means of a
slot-die head. The layers in the produced LEC device were found to be
highly uneven, and the layer thickness, for both active layer and anode,
was very thick at approximately 1 µm. However, due to the unique
self-doping operation of the LEC, the light emitted did not suffer from
the rough interfaces, and was in fact found to be very uniform. This
feature is ideal for roll-to-roll processes, as the demands of the
coating quality can be relaxed thus lowering the costs substantially.
It
is notable that all the steps involved, i.e. preparation of inks, the
subsequent coating of the constituent layers, and the final device
operation all could be executed under ambient air. This shows that the
LEC-technology can be used for a low-cost fabrication of large-area
light emitting devices under ambient air.
The
experiments were carried out in collaboration with Professor Frederik
Krebs and Henrik Dam at the Technical University of Denmark, where they
have extensive experience of low-cost roll-to-roll fabrication of
organic solar cells.
“It
was great to work with Frederik Krebs’ group so that we quickly could
prove that our 10×10 cm2 application techniques for LECs were
transferable to roll-to-roll-processing. Thanks to them we have made a
rapid technology leap in a very short time”, says Andreas Sandström, PhD
student at Umeå University.
Ludvig
Edman is the founder, and Andreas Sandström the CTO, of the company
LunaLEC in Umeå, where LECs are developed for commercial applications.
Ambient Fabrication of Flexible and Large-Area Organic Light-Emitting Devices Using Slot-Die Coating
The Organic Photonics and Electronics Group
Source: Umea University
