Planar Chiral Thermally Activated Delayed Fluorescence Materials Based on Di[2.2]paracyclophane for Circularly Polarized Electroluminescence

In this study, featuring di[2.2]paracyclophane (DpCp) amine derivatives as electron donors and 4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl (Trz) as the electron acceptor, four thermally activated delayed fluorescence (TADF) molecules are disclosed. The C2 symmetric molecules, DpCpN-Trz and DpCpCz-Trz, bearing a chair-like planar chiral di[2.2]paracyclophane moiety, are obtained as optically pure enantiomers (R/S)-C-DpCpN-Trz and (R/S)-C-DpCpCz-Trz. And the compounds B-DpCpN-Trz and B-DpCpCz-Trz with a bridge-like di[2.2]paracyclophane skeleton are meso-compounds, thus without optically activity. All emitters show blue emissions peaking from 464 to 485 nm, accompanied by high photoluminescence quantum efficiency (up to 93%). The enantiomers (R/S)-C-DpCpN-Trz and (R/S)-C-DpCpCz-Trz exhibit symmetric circularly polarized photoluminescence spectra with dissymmetry factors (|gPL|) ranging from 3.8 x 10-4 to 6.7 x 10-4 in toluene and films. The organic light-emitting diodes (OLEDs) fabricated with these emitters achieve maximum external quantum efficiencies of up to 19.5%. Notably, the circularly polarized OLEDs (CP-OLEDs) with (R/S)-C-DpCpN-Trz and (R/S)-C-DpCpCz-Trz demonstrate |gEL| factors of up to 7.6 x 10-4. This study demonstrates a feasible way to design TADF materials and enantiomers by incorporating DpCp derivatives for CP-OLEDs. Four thermally activated delayed fluorescence compounds based on planar di[2.2]paracyclophane are synthesized, and the asymmetric bridge-like configuration emitters are separated to (R/S)-C-DpCpN-Trz and (R/S)-C-DpCpCz-Trz enantiomers. These materials showed blue emissions with high photoluminescence quantum efficiencies, and the enantiomers exhibited symmetric circularly polarized luminescence spectra. The organic light-emitting diodes (OLEDs) based on four emitters exhibited high values of up to 19.5%, and the circularly polarized OLEDs with enantiomers displayed dissymmetry factors of up to 7.6 x 10-4. image