Tuning of spin-flip efficiency of blue emitting multicarbazolyl-substituted benzonitriles by exploitation of the different additional electron accepting moieties

Ornamenting of Blue Thermally Activated Delayed Fluorescence Emitters by Anchor Groups for the Minimization of Solid-State Solvation and Conformation Disorder Corollaries in Non-Doped and Doped Organic Light-Emitting Diodes

“…13 Exploiting strong electron-withdrawing inductive effects of the trifluoromethyl group, in our previous work, we developed asymmetric multi-carbazole-based emitters by utilizing two different types of electron-withdrawing moieties which helped to improve their TADF properties and to achieve efficient blue emission. 14 These and other examples prove that efficient triplet exciton utilization is possible using multi-channel RISC of multi-donor−acceptor molecules as well as obtaining small singlet-triplet energy splitting (ΔE ST ) resulting from through space and bond charge transfer effects of the molecules. 15 It could be expected that the alternating arrangement of donor and acceptor units may lead to the coexistence of through-bond charge transfer (TBCT) and through-space charge transfer (TSCT) effects, resulting in a small ΔE ST and high photoluminescence quantum yield (PLQY).…”

“…600 h at brightness of 1000 cd×m –2 and maximum EQE of 29.3%) of sky-blue TADF OLEDs with electroluminescence (EL) spectrum peaking at 486 nm was observed using 9,9′,9″,9‴,9‴′-[6-(4,6-diphenyl-1,3,5-triazine-2-yl)­benzene-1,2,3,4,5-pentayl]­pentakis­(9 H -carbazole) as blue TADF emitter with extremely fast spin-flipping characterized by reverse intersystem crossing (RISC) rate of 1.5 × 10 7 s –1 . Exploiting strong electron-withdrawing inductive effects of the trifluoromethyl group, in our previous work, we developed asymmetric multi-carbazole-based emitters by utilizing two different types of electron-withdrawing moieties which helped to improve their TADF properties and to achieve efficient blue emission . These and other examples prove that efficient triplet exciton utilization is possible using multi-channel RISC of multi-donor–acceptor molecules as well as obtaining small singlet-triplet energy splitting (Δ E ST ) resulting from through space and bond charge transfer effects of the molecules .…”

Synthetic progress of organic thermally activated delayed fluorescence emitters via C–H activation and functionalization

“…Based on this, Grazulevicius's group designed a series of tetrafluorocyanobenzenes with linked additional electronaccepting moieties, obtaining four blue-emitting TADF emitters (CNCN, CNCF 3 , CNCOA, and CNCOAM) through simple nucleophilic substitution reactions (Scheme 14c). 96 These emitters, with fine-tuned structures, all displayed blue TADF emission. The introduction of the additional acceptor moieties through CÀH activation not only provided varying electron accepting abilities but also enabled different non-covalent intramolecular interactions (e.g., CÀHÁ Á ÁF, O, and N hydrogen bonds), significantly impacting key photophysical parameters such as PLQYs and k RISC s. The practical CÀH activation used in this work provided practical synthetic routes for constructing a series of structurally similar TADF emitters and offered opportunities for studying structure-property relationships.…”

“…Based on this, Grazulevicius's group designed a series of tetrafluorocyanobenzenes with linked additional electron-accepting moieties, obtaining four blue-emitting TADF emitters (CNCN, CNCF 3 , CNCOA, and CNCOAM) through simple nucleophilic substitution reactions (Scheme 14c). 96 These emitters, with fine-tuned structures, all displayed blue TADF emission. The introduction of the additional acceptor moieties through C−H activation not only provided varying electron accepting abilities but also enabled different non-covalent intramolecular interactions ( e.g.…”

Effects of variation in phenylpyridinyl and di-tert-butyl-carbazolyl substituents of benzene on the performance of the derivatives in colour-tuneable white and exciplex-based sky-blue light-emitting diodes

“…This value is much higher than the T g (84-109 1C) of previously reported di-tert-butyl-carbazole-based TADF materials. 31 It is also considerably higher than T g of most organic semiconductors used in OLEDs, including 4CzIPN with a T g of 176 1C. 32 The possible reasons for the high T g of 4tCzPy can be its relatively high molecular weight and the ability of the pyridine moiety to take part in hydrogen bonding.…”