Through‐Space Charge‐Transfer Polynorbornenes with Fixed and Controllable Spatial Alignment of Donor and Acceptor for High‐Efficiency Blue Thermally Activated Delayed Fluorescence

Abstract

Through-space charge transfer polynorbornenes with fixeda nd controllable spatial alignment of donor and acceptor in edge-to-face/face-to-face stacking patterns are developed for achieving high-efficiency blue thermally activated delayed fluorescence (TADF). The alignment is realized by using the cis,e xo-configuration of norbornene to confine donor and acceptor in close proximity, and utilizing orthogonal and dendritic structures of donors to provide either perpendicular or parallel stackingm otif relative to acceptors. Compared to edge-to-face counterparts,polynorbornenes with face-to-face aligned donor and acceptor exhibit muchl arger oscillator strength and higher photoluminescence quantum yield. The resulting polymers exhibit deep blue (422 nm) to sky blue (482 nm) emission and TADF effect with reverse intersystem crossing rates of 0.4-5.9 10 6 s À1 ,giving the maximum external quantum efficiency of 18.8 %f or non-doped blue organic light-emitting diodes by solution process.

Face‐to‐Face Orientation of Quasiplanar Donor and Acceptor Enables Highly Efficient Intramolecular Exciplex Fluorescence

“…The maximum brightness of 75 100 cd m −2 is remarkably high among the TSCT emitters in the literature. Although the maximum EQE of 17.95 % is comparable to that in DPEPO host, its roll‐off was found to be as small as only 1.1 % at 1000 cd m −2 (Figure 4 d), which is among the best values for OLEDs regardless of the emission mechanism [8] . Even at the brightness of 10 000 cd m −2 , the EQE remains >15 %.…”

“…Recently, advances of manipulating the cofacial π‐π interaction have been made through elegant choice or design of molecular scaffolds to accommodate the donor and acceptor (Figure 1 d). [8, 9] Thanks to these conformational engineering, the photo‐ and electroluminescence efficiencies have been remarkably enhanced due to the suppressed nonradiative decay and/or accelerated RISC. Nevertheless, the tuning of radiative decay has not been unveiled and the distance between donor and acceptor in these molecules is still too longer for effective face‐to‐face π‐π interaction to occur.…”

Through‐space charge transfer polymers for solution‐processed organic light‐emitting diodes

“…Besides polystyrene‐based ones, another kind of TSCT polymers are constructed with polynorbornene as nonconjugated backbone. [ 65 ] Unlike polystyrene‐based TSCT polymers where donor and acceptor are attached to different repeating units and could motion freely relative to each other, polynorbornene‐based TSCT polymers have two advantages. First, norbornene monomer itself can act as a rigid skeleton to fix donor and acceptor in one repeating unit, limiting the free rotation of donor and acceptor segments around polymer backbone.…”

Harvesting triplet excitons for near-infrared electroluminescence via thermally activated delayed fluorescence channel

“…As for the molecular design, besides the classical ICT, the emerging through space charge transfer (TSCT) ( Tang et al., 2020 ; Yang et al., 2020c ; Peng et al., 2020 ; Wada et al., 2020 ; Tsujimoto et al., 2017 ; Li et al., 2020a ), MR-TADF ( Hatakeyama et al., 2016 ; Xu et al., 2020 ), and these hybridizations would be potential choices for the realization of efficient TADF channels in the NIR region in the future. As for the TSCT-based TADF emitters, electron donors and acceptors usually have a spatial face-to-face alignment through a rigid linker.…”