Chiral Conjugated Thermally Activated Delayed Fluorescent Polymers for Highly Efficient Circularly Polarized Polymer Light-Emitting Diodes

Two novel chiral conjugated polymers R-P and S-P designed and synthesized from a pair of circularly polarized thermally activated delayed fluorescence (CP-TADF) enantiomers are presented in this work. The two polymers exhibited excellent TADF properties with small singlet-triplet energy gaps (ΔEST) of 0.045 and 0.061 eV and relatively high photoluminescence quantum yields (PLQYs) of 72 and 76%, respectively. Besides, intense mirror-image circularly polarized luminescence signals were detected from R-P and S-P in both solution and film states with dissymmetry factors (|glum|) of up to 1.9 × 10-3. Furthermore, solution-processed circularly polarized polymer light-emitting diodes (CP-PLEDs) fabricated with R-P and S-P achieved high maximum external quantum efficiencies of 14.9 and 15.8% and high maximum brightness (Lmax) of 8940 and 12,180 cd/m2 with yellowish-green emission peaks at 546 and 544 nm, respectively. Moreover, intense circularly polarized electroluminescence signals with electroluminescence dissymmetry factors (gEL) of -1.5 × 10-3 and +1.6 × 10-3 were detected from the CP-PLED devices fabricated with R-P and S-P, respectively.