Highly Efficient Blue Organic Light‐Emitting Devices Based on “Cross”‐Shaped Hot Exciton Emitters

Abstract The development of blue electroluminescent (EL) materials remains a significant challenge in organic light‐emitting diode (OLED) technology. In this study, a novel design strategy is proposed for blue hot exciton (HE) materials, which involves utilizing a “cross” shaped molecular structure characterized by substantial steric hindrance and a highly twisted conformation. The unique cross‐shaped molecular architecture with distinct “arms” enables flexible control over the excited state properties of the molecule, thereby facilitating precise modulation of high‐lying triplet and low‐lying singlet excited state energy levels. Furthermore, the 3D spatial configuration of the molecule effectively reduces close molecular packing, thereby minimizing the risk of material concentration quenching. The proof‐of‐concept HE emitters CN‐PI and TP‐PI exhibit non‐π‐π stacking configurations in single crystals, achieving high photoluminescence quantum yield (PLQY) values up to 51.3% and 46.5% in non‐doped thin films, respectively, along with rapid radiation decay rates and reasonable distribution of T_m (m ≤ 5) and S₁ states. Non‐doped OLEDs incorporating these emitters demonstrate exceptional external quantum efficiencies (EQE), reaching 7.3% and 6.4%, respectively, while exhibiting minimal efficiency roll‐off at high luminance. This research introduces a promising approach for developing high‐performance blue HE emitters.