Suppression of Efficiency Roll-Off in Fluorescent Organic Light-Emitting Devices Through Charge Carriers and Excitons Management

In this paper, a novel design for the emission layer of the fluorescent organic light-emitting devices is presented to suppress the efficiency roll-off and maintain the high efficiency at both low and high current regimes. In the emission layer, the emitter material is blended with a manager or host material with proper charge carrier transporting and excitonic energy levels. The charge carriers and excitons undergo a carefully designed route in this manager–emitter blend so that the triplet excitons always contribute positively to the efficiency through triplety–triplet annihilation (TTA), and the competing mechanisms are severely weakened. The required characteristics of the emitter and host materials for the proper functioning of the proposed strategy are completely discussed in this paper. The proposed scheme is verified through detailed numerical simulations, and it is shown that the efficiency roll-off can be effectively suppressed. The overall efficiency depends on the TTA yield in producing singlet excitons. For the yield of 0.5, an internal quantum efficiency of 50% at the current density of 10 mAcm
$^{-2}$
is computed, which increases as the triplet density increases reaching the value of 58% at the current density of 1 Acm
$^{-2}$
.