Abstract
The most critical scientific problem for efficient blue emitters is to solve the inherent contradiction between wide bandgap characteristics and difficult carrier injection/unbalanced transmission. Herein, three donor-π-acceptor (D-π-A) type blue materials (TPACFTAZ, 9PCZCFTAZ, and 3PCZCFTAZ) based on fluorene-bridged and triazine acceptors were designed and synthesized. By regulating the donor strength and substitution sites, the synergistic optimization of solid-state aggregation mode and excited state characteristics has been achieved. Single crystal analysis shows that 3PCZCFTAZ exhibits the most abundant and effective intermolecular forces, obtaining fast-balanced carrier transport with electron and hole transport rates of 10.60 × 10(-5) cm(2) V(-1) s(-1) and 9.53 × 10(-5) cm(2) V(-1) s(-1), respectively. Moreover, 3PCZCFTAZ also accomplished sufficient and stable hybridization between localized excited (LE) and charge transfer (CT) states, with a solid-state photoluminescence quantum yield (PLQY) of 71.2% and exciton utilization efficiency (EUE) of 82.2%. More importantly, the non-doped device based on 3PCZCFTAZ achieved a high EQE of 11.7%, with an efficiency roll-off of 0 @1000 cd m(-2). Among similar non-doped devices, this device exhibits not only negligible efficiency roll-off at high brightness, but also ranks among the most efficient reported to date.