P‐255: <i>Late‐News Poster:</i> The Energy Transfer and Utilization Mechanisms of Dual‐EML Blue OLEDs

In current commercializing OLED panels, blue devices still mainly utilize traditional fluorescent emission mechanisms due to the shorter lifetime and low color purity of blue PH‐OLEDs and TADF‐OLEDs. Despite the internal quantum efficiency (IQE) can be achieved 62.5% by using commercial blue host materials with Triplet‐Triplet Fusion (TTF) characteristics, the external quantum efficiency (EQE ) of blue fluorescent devices doesn't look respectable on account of incomplete utilization of triplet excitons, such as aggregation‐caused quenching (ACQ) and triplet‐polaron quenching (TPQ). In recent years, the dual‐EML blue devices were developed to improve efficiencies of fluorescence OLEDs. However, the energy transfer and utilization mechanisms are still unclear understanding. To accelerating the commercialization of Dual‐EML blue devices, our team present a novel device structure system to analysis the different energy utilization mechanisms between EML1 and EML2. The blue device exhibits high efficiency~300 BI and great improvement of lifetime ~80%, and providing valuable insights in both selecting well‐matched BH materials and optimizing device structure.