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

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.