Engineering High-Efficiency Anthracene-Based Deep-Blue Emitters via Spirofluorene Bridge-Mediated Electronic Structure Modulation
Deep-blue organic light-emitting diodes (OLEDs) remain the most challenging primary-color emitters due to stringent exciton energy requirements. We strategically designed two innovative deep-blue emitters, SCZ-4AnCN and STPA-4AnCN, via systematic functionalization of an anthracene core with arylamino-decorated spirofluorene donors and cyano-substituted phenyl acceptors. Comprehensive theoretical and experimental analyses demonstrate that these spirofluorene-anthracene hybrids adopt precisely engineered distorted configurations, effectively suppressing detrimental intermolecular π–π stacking in condensed phases. The sp3-hybridized bridgehead carbons in spirofluorene units play a pivotal role by simultaneously restricting π-conjugation extension and fine-tuning donor–acceptor interactions, thereby stabilizing the lowest excited singlet (S1) state with dominant local excitation (LE) character. This molecular engineering yields exceptional deep-blue emission with remarkable efficiency. Notably, the materials exhibit unique high-lying reverse intersystem crossing (hRISC) behavior, enabling efficient triplet harvesting. Optimized doped devices incorporating SCZ-4AnCN achieve outstanding performance, including a maximum external quantum efficiency (EQE_max) exceeding 10% and CIE coordinates (0.154, 0.052) approaching the BT.2020 blue standard. Nondoped devices maintain impressive performance with an EQE_max of 7.51% and superior operational stability, demonstrating less than 10% efficiency roll-off at 1000 cd m−2. This work validates anthracene-based molecular architectures for deep-blue electroluminescence and establishes a transformative design paradigm for next-generation OLED emitters.