Impact of Spontaneous Orientation Polarization in the Emission Layer on the Charge Accumulation and Exciton−Polaron Quenching Properties of Ir-Complex-based Organic Light-Emitting Diodes

Controlling the charge accumulation properties of organic light-emitting diodes (OLEDs) is crucial for optimizing the device performance. In particular, the charge distribution in the vicinity of the emission layer (EML) affects the device efficiency and lifetime, as it determines the emission zone and exciton−polaron quenching (EPQ) characteristics. This study investigates the impact of spontaneous orientation polarization (SOP) in the EML on the charge accumulation and EPQ characteristics of Ir-complex-based OLEDs using displacement current measurements combined with photoluminescence intensity measurements and device simulations. A significant SOP is induced in the EML depending on the SOP-active material content, which modifies the accumulated charge distribution in the EML. Notably, the SOP can suppress the EPQ, particularly when the energy offset at the interface between the hole transport layer and the EML is small. These findings highlight the importance of SOP in optimizing the OLED device performance.