Regio-isomeric effect of dibenzofuran-based host materials on photophysics and device performance in organic light-emitting diodes

Abstract Three new host materials, namely, 1-DBF-PCz, 2-DBF-PCz, and 4-DBF-PCz, were designed and synthesized based on a dibenzofuran unit connected to a phenylcarbazole at different linkage positions. Their photophysical, electrochemical, and thermal properties were studied. Green thermally activated delayed fluorescent (TADF) organic light-emitting diodes (OLEDs) were fabricated with 4CzIPN as a standard TADF emitter. 15 wt% 4CzIPN-doped OLEDs based on 1-DBF-PCz, 2-DBF-PCz, and 4-DBF-PCz showed the maximum external quantum efficiencies of 13.3%, 14.6%, and 14.0%, respectively, which were comparable to that of the reference device based on mCBP (14.8%). In addition to the comparable device efficiencies, devices based on 1-DBF-PCz and 2-DBF-PCz showed longer device stabilities with LT95 (95% of the initial luminance) of 67 and 56 h, compared to the mCBP-based device (30 h). The lengthened device stability was attributed to more balanced hole/electron-transport properties of the host layers.