Ultrahigh-Efficiency Sensitization in Hyperfluorescence WOLEDs via Low-Cost Planar Source Evaporation

The industrial advancement of white organic light-emitting diodes (WOLEDs) remains constrained by the inherent conflict between high manufacturing costs and stringent performance requirements. Here, we demonstrate a breakthrough in all-fluorescent WOLEDs by simultaneously addressing the intrinsic efficiency limitations of two-color emitters and the complexity of conventional fabrication. We systematically investigated two-color WOLEDs, uncovering the critical role of triplet–triplet annihilation in their efficiency degradation. To overcome these bottlenecks, we first designed and realized high-efficiency three-color WOLEDs incorporating sky-blue, deep-blue, and orange emission layers, based on 5tCzBN, DABNA-1, and 4CzTPNBu dopants in an mCBP bipolar host. Efficient Förster resonance energy transfer, enabled by 5tCzBN sensitization and 4CzTPNBu electron trapping, produced directional excitation of both blue and orange fluorophores, yielding state-of-the-art white electroluminescence with chromatic coordinates (0.326, 0.321). Importantly, we further introduced a planar source evaporation (PSE) technique, which replaces multicomponent microdoping with a material-efficient process, enabling low-cost fabrication of high-performance OLEDs. As a result, our three-color devices reached maximum external quantum efficiency (EQEmax) to 17.24%, while optimized three-color WOLEDs achieved a maximum current efficiency (CEmax) of 69.78 cd/A and EQEmax to 26.35%, alongside low turn-on voltage, high brightness, and an LT50 exceeding 100,000 h (@ 100 cd/m2). By uniting mechanism-level insights with process-level innovation, this work establishes a cost-effective and scalable route for next-generation WOLEDs in lighting and display applications.