Reducing the efficiency roll-off in organic light-emitting diodes at high currents under external magnetic fields

Singlet-polaron and triplet-polaron annihilation mechanisms are the most detrimental exciton quenching processes that lower the efficiency of organic light-emitting diodes (OLEDs) at high current densities, causing so-called efficiency roll-off in these devices. These exciton loss mechanisms are also the critical obstacles towards the realization of electrically pumped organic semiconductor lasers, which require very high current densities to reach threshold. Herein, under a relatively large external magnetic field, we demonstrate that the efficiency roll-off at high current densities in europium (Eu3+)-based solution-processed OLEDs can be suppressed to some extent while the luminance is enhanced. We achieve this by reducing the Forster-type exciton-polaron annihilation processes. Under the applied magnetic field, we show that manipulation of the polaron-spin and exciton dynamics lead to a quantitative roll-off suppression.

Automated summary

Singlet-polaron and triplet-polaron annihilation mechanisms are the main causes of efficiency roll-off in OLEDs at high current densities, hindering the development of electrically pumped organic semiconductor lasers. By reducing Forster-type exciton-polaron annihilation processes under a large external magnetic field, efficiency roll-off can be suppressed in europium-based solution-processed OLEDs while enhancing luminance. Manipulation of polaron-spin and exciton dynamics under the applied magnetic field leads to quantitative roll-off suppression.