Samsung Advanced Institute of Technology

Defects present in the hole transport layer (HTL) of a phosphorescent organic light emitting diode (PHOLED) have a significant impact on both charge and exciton behavior, degrading device’s electrical and optical performance. These HTL defects trap holes, hindering their injection into the emission layer (EML) and inducing additional electron supply to maintain the electric current across the device. Consequently, excitons are highly concentrated at the HTL/EML interface, reducing device efficiency by ~8% due to intensified bimolecular annihilations. Moreover, HTL defects located within a proximity of ≤ 8 nm from the interface directly and remotely quench excitons originating from the EML, reducing device efficiency by up to ~74%. This interfacial exciton quenching is governed by both Dexter and F？rster energy transfer, exhibiting a strong distance dependence. Our study highlights the crucial role of the HTL/EML interface in high-performance PHOLEDs, necessitating effective prevention of defect formation near the interface.