Electron-withdrawing Group Modified Carbazolophane Donors for Deep Blue Thermally Activated Delayed Fluorescence OLEDs

Abstract

We report two blue-emitting thermally activated delayed fluorescence (TADF) compounds employing a substituted carbazolophane (Czp) donor (indolo[2.2]paracyclophane). The compounds CNCzpPhTRZ and CF3CzpPhTRZ show emission maxima of 426 nm and 432 nm, respectively, with high photoluminescence quantum yields (PL) of 73% and 80%, respectively. The singlet-triplet energy gap (EST) of both emitters is 0.22 eV, resulting in long-delayed lifetimes of 132 μs for CNCzpPhTRZ and 158 μs for CF3CzpPhTRZ in PPT as the host matrix. Blue organic light-emitting diodes (OLEDs) showed maximum external quantum efficiencies (EQEs) of 7.4% for CNCzpPhTRZ and 11.6% for CF3CzpPhTRZ with electroluminescence maxima of ca. 460 nm.