Organic Light-Emitting Electrochemical Cells for Lighting Applications

Light-emitting electrochemical cells (LECs) are single-layer, solution-processible, solid-state, light-emitting devices comprising a luminescent material in an ionic environment. Their peculiar operational mechanism, involving the migration of ions in response to an applied electrical field, allows for charge carrier injection from air-stable electrodes and low driving voltages, close to the band gap potential of the light-emitting species used, giving rise to high luminous efficacies. All of the latter aspects make LECs an appealing alternative for lighting applications and have revived the vision of an uninterrupted, high-throughput manufacturing of cost-effective and large-area light sources under ambient conditions.

Apart from the undeniable benefits, the performance of LECs is, however, still distant from state-of-the-art organic light-emitting diodes (OLEDs) which is at least partially accounted for by the insufficient understanding of the physical processes during their operation. The present work mediates a deeper view in the physics and dynamics of LECs based on an orange-emitting iridium(III) ionic transition metal complex. With the aid of the insights obtained, the performance of LECs is significantly enhanced namely by an adaptation of the operating terms, by an optimization of the preparation conditions and by a modification of the device architecture.

The unification of all optimization achievements gives rise to LECs featuring an instant response at a high brightness of >500 cd/m² and an unprecedented lifetime of nearly 7000 h at a brightness of more than 1000 cd/m². The results stir up hope that LECs will become even more the focus of attention as possible simple future illuminants.