Through-Space Conjugated Molecule with Dual Delayed Fluorescence and Room-Temperature Phosphorescence for High-Performance OLEDs

Abstract

Purely organic materials with room-temperature phosphorescence usually have much longer triplet state lifetimes than noble-metal containing phosphorescent materials, which lead to severe exciton quenching and inferior electroluminescence (EL) performance when applied in organic light-emitting diodes (OLEDs). Herein, a novel through-space conjugated molecule (2,3-PICz-XT) with dual delayed fluorescence and room-temperature phosphorescence is developed. Owing to suitable energy levels and strong spin–orbit coupling among excited states, 2,3-PICz-XT has short phosphorescence lifetimes at microsecond scale and high photoluminescence quantum yields in neat and doped films. 2,3-PICz-XT can function as efficient emitters in OLEDs, providing high external quantum efficiencies (ηexts) of up to 32.73% with small efficiency roll-offs. It can also efficiently sensitize various phosphorescent and thermally activated delayed fluorescence (TADF) materials to yield excellent EL performances. Impressively, the hyperfluorescence OLEDs using 2,3-PICz-XT as sensitizer for multiple resonance TADF materials attain narrow EL spectra and greatly improved ηexts over 35%. To the best of our knowledge, 2,3-PICz-XT is the most efficient emitter and sensitizer ever reported for dual delayed fluorescence and phosphorescence materials.