Chiral Spiro‐Axis Induced Blue Thermally Activated Delayed Fluorescence Material for Efficient Circularly Polarized OLEDs with Low Efficiency Roll‐Off

Abstract

A spiro‐axis skeleton not only introduces circularly polarized luminescence (CPL) into thermally activated delayed fluorescence (TADF) molecules but also enhances the intramolecular through space charge transfer (TSCT) process. Spiral distributed phenoxazine and 2‐(trifluoromethyl)‐9H‐thioxanthen‐9‐one‐10,10‐dioxide act as donor and acceptor units, respectively. The resulting TADF enantiomers, (rac)‐OSFSO, display emission maxima at 470 nm, small singlet‐triplet energy gap (ΔEST) of 0.022 eV and high photoluminescence quantum yield (PLQY) of 81.2 % in co‐doped film. The circularly polarized OLEDs (CP‐OLEDs) based on (R)‐OSFSO and (S)‐OSFSO display obvious circularly polarized electroluminescence (CPEL) signals with dissymmetry factor up to 3.0×10−3 and maximum external quantum efficiency (EQEmax) of 20.0 %. Moreover, the devices show remarkably low efficiency roll‐off with an EQE of 19.3 % at 1000 cd m−2 (roll‐off ca. 3.5 %), which are among the top results of CP‐OLEDs.

Highly Efficient Sky‐Blue π‐Stacked Thermally Activated Delayed Fluorescence Emitter with Multi‐Stimulus Response Properties

“…Moreover, the g lum of (R)-SDMAC and (S)-SDMAC is up to À 1.19 × 10 À 3 and + 1.39 × 10 À 3 , respectively (Figure 4D), which is consistent with most CP-TADF molecules reported in the literature. [6,32,60,61] We also tested the enantiomeric excess and CPL properties of the sample after sublimation and found that they were consistent with the properties before sublimation (Figures S21-S23).…”

Iridium(iii) complexes incorporating thieno[2,3-d]pyrimidine units for efficient orange-to-yellow electroluminescence with low efficiency roll-off

“…34 The HOMO energy levels were obtained via the oxidation potential of each complex using the equation of E HOMO = −[ E OX − E (Fc/Fc+) + 4.8] eV and estimated to be −5.61 and −5.62 eV for (4tfptp) 2 Ir(tpip) and (4tfptp) 2 Ir(Stpip), respectively. 35 The energy level gaps ( E gap ) of (4tfptp) 2 Ir(tpip) and (4tfptp) 2 Ir(Stpip) complexes were calculated from the UV-vis absorption spectra as 2.14 and 2.24 eV, respectively (Table 1). Therefore, the LUMO energy levels were estimated as −3.47 and −3.38 eV for (4tfptp) 2 Ir(tpip) and (4tfptp) 2 Ir(Stpip), respectively, with the equation of E LUMO = E HOMO + E gap .…”

Intramolecular Through-Space Charge-Transfer Emitters Featuring Thermally Activated Delayed Fluorescence for High-Efficiency Electroluminescent Devices

“…The high kRISC values of 1-5 indicate that they can efficiently consume triplets for emission, alleviating triplet-triplet/triplet-polaron annihilations [48][49][50][51]. By broadening the recombination zones with optimized device structures, the efficiency roll-offs would be suppressed [35,36]. The high device efficiencies indicate that 1-5 are promising functional materials for high-performance EL devices.…”

“…Recent researches have proved that cofacial D/A alignments are favored for developing efficient TSCT emitters [25][26][27][28][29][30][31][32][33][34][35][36][37][38], which can reinforce TSCT and promote radiative decay of charge-transfer states [35,37]. Very recently, Jiang and Liao et al…”