Kinetic Pathways of Excitons and Polarons Governing Device Degradation in Exciplex-Forming Co-Host-Based Organic Light-Emitting Diodes

The exciplex-forming cohost with thermally activated delayed fluorescence characteristic has been used for achieving a long operational lifetime and high efficiency in phosphorescent organic light-emitting diodes (PHOLEDs). In this work, the intrinsic polaron dynamics in the device are comprehensively investigated in terms of the polaron and exciton behaviors through the numerical simulation with transient electroluminescence (EL). Furthermore, the degradation mechanism generated by bimolecular interaction is investigated by considering the reduction of the luminance and voltage rising. As a result, the polaron, exciton, and recombination coefficient could be quantified via numerical simulation. Based on this, it is revealed that suppressing the exciton-polaron interaction is crucial to improving the long operational lifetime in exciplex forming cohost based PHOLEDs.