A dual rigid donor and acceptor enabling red thermally activated delayed fluorescence emitters for efficient OLEDs with low efficiency roll-off

Abstract

Two new deep-red TADF emitters with the integrating of dual rigid donor and acceptors are elaborately designed. Electroluminescent devices employing them as emitting layers achieve high external quantum efficiency (EQE)...

Efficient thermally activated delayed fluorophores featuring multi-donor arms and a π-extended acceptor core

“…In general, most twisted D-A type TADF emitters exhibit near-zero oscillator strength ( f ) due to their perpendicular D–A structure, which results in compromised photoluminescence quantum yields (PLQYs), especially pronounced in long-wavelength emitters. 22 However, in our case, both 4CzAQ and 4CzDP demonstrate moderate-to-large D–A twisting angles just exceeding 60°. Although the HOMOs and LUMOs of 4CzAQ and 4CzDP mainly localize on the donor units and the π-extended acceptor, respectively, there is still discernible HOMO/LUMO overlap on the terminal fused benzene ring of the acceptors, resulting in the non-vanishing f values of 0.023 and 0.021 for 4CzAQ and 4CzDP .…”

“…19 To mitigate emission quenching, the emissive materials must be dispersed within a suitable host material at low concentrations (<5 wt%). 20–22 Nevertheless, this method also brings about additional issues, such as insufficient host-to-guest energy transfer, 23 imbalanced charge transport, 6 and the need for precise regulation of the evaporation rate during device fabrication.…”

Red-shift emission and rapid up-conversion of B,N-containing electroluminescent materialsviatuning intramolecular charge transfer

“…S19 and Table S4, ESI†). 4,14,16,34–59 Although the orange-red device displays high EQE and low efficiency roll-off, we expect to find a suitable TADF sensitizer that will be employed to further improve device efficiency and stability.…”

Integration of fine-tuned chiral donor with hybrid long/short-range charge-transfer for high-performance circularly polarized electroluminescence

“…11 This predicament is often encountered in donor–acceptor type TADF systems characterized by extensive steric hindrance and long-range charge-transfer (LR-CT) excitation. 12 Conversely, the simultaneous integration of electron-rich and electron-deficient atoms within a polycyclic aromatic hydrocarbon ring gives rise to a multiple-resonance (MR) effect and short-range charge-transfer (SR-CT) excitation, 13 yielding enhanced f and accelerated radiative decay rates ( k r ), while incurring less favorable Δ E ST and reverse intersystem crossing rates ( k RISC ). 14 Recent endeavors by Duan et al have showcased a viable resolution by introducing MR acceptor groups onto a sterically unencumbered donor segment, resulting in a hybrid configuration characterized by both LR-CT and SR-CT excitation.…”