Constructing thermally activated delayed fluorescence dendrimers for solution processable blue OLEDs by molecular engineering of peripheral dendrons

Thermally activated delayed fluorescence (TADF) dendrimers with definite chemical structure are ideal candi-date to fabricate high-efficiency organic light emitting diodes (OLEDs) using lower-cost solution processing techniques. Nevertheless, there still remains a challenge to construct molecular architectures of dendrimer-based TADF emitters that show easily controlled photophysical properties and superior carrier transporting capability simultaneously. Herein, we integrate peripheral dendrons possessing bipolar transmission capability with donor -acceptor skeleton through spiro junction to construct newly designed dendritic TADF emitters, TrzSpiroAc-tmCP and TrzSpiroAc-tmCPCN. By precisely regulating peripheral dendrons in these newly designed molecules, the lifetime and proportion of delayed components for TrzSpiroAc-tmCPCN are meticulously modulated to be 3.1 mu s and 26.0 %, respectively, and thus exhibiting enhanced reverse intersystem crossing process with rate constant of 3.2 x 105 s-1 and excellent photoluminescence quantum yield over 70 %. Solution processable OLEDs based on TrzSpiroAc-tmCPCN with blue emission are achieved, and the external quantum efficiency value can exceed 10 %. Overall, this work manifests a valid strategy to tackle the imperative need for further exploring high-efficiency TADF dendrimers by integrating molecular engineering of peripheral dendritic units with constructing spiro junction between emission core and dendritic units.