Highly Efficient Non‐Doped Blue Electro‐Fluorescence With Fast Carrier Mobilities: Hybrid Local and Charge‐Transfer (HLCT) Excited State and Regularly Stacked Aggregate

Abstract

ABSTRACT Non‐doped organic light‐emitting diodes (OLEDs) offer simpler fabrication and lower manufacturing costs than traditional doped OLEDs, attracting increasing attention in both scientific research and industrial applications. However, aggregation‐caused quenching (ACQ) and unbalanced carrier transport remain major bottlenecks to achieving efficient non‐doped OLEDs, especially the primary‐blue fluorescent OLEDs. Herein, we report three novel blue or deep‐blue emitters with excellent non‐doped OLED performance of near 15% external quantum efficiency (EQE), which can be assigned to the synergistic contributions of intramolecular hybrid local and charge‐transfer (HLCT) excited state character and intermolecular aggregation pattern. The incorporation of a fluorene π‐bridge in the three molecules not only contributes to the high photoluminescence quantum yield (PLQY), high blue color purity and satisfactory exciton utilization efficiency (EUE), but also to the regulated π‐stacking that gives rise to both light outcoupling efficiency, with horizontal dipole orientation factor (Θ // ) exceeding 90%, and boosted carrier mobilities (at 5.0 × 10 5 V·m −1 , hole: ∼ 2.76 × 10 −5 cm 2 ·V −1 ·s −1 ; electron: ∼ 2.51 × 10 −4 cm 2 ·V −1 ·s −1 ) in non‐doped OLEDs.