Synergistic Intramolecular Non-Covalent Interactions Enable Robust Pure-Blue TADF emitters

Abstract Stability-issues of organic light-emitting diodes (OLEDs) employing thermally activated delayed fluorescence (TADF) require further advancements, especially in pure-blue range of CIEy<0.20, existing a dilemma between color purity and device lifetime. Though improving bond-dissociation-energy (BDE) could effectively improve material intrinsic stability, strategies to sufficiently improve BDE without negative effects on photophysical performances are still lacking. Herein, we disclose that synergistic intramolecular non-covalent interactions (Intra-NI) can achieve not only the highest C-N BDE among blue TADF materials, but enhanced molecular-rigidity, near-unity photoluminescent quantum yields and short delayed lifetime. Pure-blue TADF-OLEDs based on proof-of-concept TADF material realize high external-quantum-efficiency and record-high LT80@500 cd m-2 of 109 h with CIEy=0.16. Furthermore, deep-blue TADF-sensitized devices exhibit state-of-the-art LT80@500 cd m-2 of 81 h with CIEy=0.10. Our findings provide new insight into the critical role of Intra-NI in OLED materials and open the way to tackling vexing stability issues for developing robust pure-blue organic emitters and other functional materials.