Exploring Efficient Blue TADF Materials with Ultrafast Bipolar Charge Transport for High-Efficiency Thick-Layer OLEDs

Achieving strong solid-state photoluminescence and fast charge transport simultaneously for organic molecules is of significant importance but challenging because of the trade-off between these properties. Herein, two tailored blue luminescent molecules constructed with ring-fused carbonyl-containing electron acceptors and spiro-acridine electron donors are developed. Owing to ordered long-range molecular alignment with proper interaction energies, their neat films exhibit ultrafast bipolar charge transport and strong delayed fluorescence with high quantum yields and short lifetimes. In doped organic light-emitting diodes (OLEDs), both molecules display eminent electroluminescence performances with excellent external quantum efficiencies (EQEs) of 40.6%. They also exhibit brilliant blue lights with record-beating EQEs of 30.2% in non-doped thin-layer OLEDs, and more importantly, high-performance simplified non-doped thick-layer OLEDs are achieved, rendering lowered driving voltages, and the best EQEs of 23.0% with tiny efficiency roll-offs. In addition, using them as sensitizers, remarkable EQEs of 40.1% and 23.2% with ultrasmall efficiency roll-offs are realized in blue hyperfluorescence thin-layer and thick-layer OLEDs, respectively. The operational lifetimes are obviously elongated matter in non-doped thick-layer devices or hyperfluorescence thick-layer devices. This work provides promising candidates for efficient simplified thick-layer OLEDs and opens a new avenue toward organic molecules with strong delayed fluorescence and fast charge transport simultaneously. Ultrafast bipolar charge transport and strong blue delayed fluorescence are realized in neat films of novel organic molecules constructed with ring-fused carbonyl-containing electron acceptors and spiro-acridine electron donors, and high-performance non-doped thin-layer OLEDs and simplified non-doped thick-layer OLEDs with record-beating EQEs of 30.2% and 23.0% and tiny roll-offs are achieved. image