Efficient narrowband electroluminescence based on a hetero-bichromophore thermally activated delayed fluorescence dyad

A hetero-bichromophore thermally activated delayed fluorescence (TADF) emitter named BOQAO was designed and synthesized, which consists of two multi-resonance TADF (MR-TADF) cores, tBuBO and tBuQAO. The short-range intramolecular charge transfer (ICT) characteristics of tBuBO and tBuQAO weaken its electron-donating and electron-withdrawing ability, respectively. Thus, weak long-range ICT from tBuBO to tBuQAO is established in BOQAO for holding blue fluorescence emission with a slight redshift, keeping a small FWHM, and maintaining the TADF properties, simultaneously. The simple doped devices exhibited high color purity with FWHMs of less than 35 nm in a wide doping ratio range from 1 wt% to 40 wt%. At a 5 wt% doping ratio, the device based on BOQAO exhibited the best device performance with an EQE of 21.8% and an FWHM of 32 nm. This work provides a simple and practical strategy for suppressing aggregation-induced spectral broadening for the development of MR-TADF.

Automated summary

A new thermally activated delayed fluorescence emitter BOQAO was designed and synthesized, which showed blue fluorescence emission and delayed fluorescence properties through the synergistic effect of two cores. It also effectively suppressed the spectral broadening phenomenon.