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.

Carbene-metal complexes as molecular scaffolds for construction of through-space TADF emitters

“…For through-space CT process this can be induced by arranging the D and A fragments closer to the face-to-face configuration. The consequence for such structural change is a characteristic PL redshift, 38,46 which, indeed, is observed in the case of TADF1 emission.…”

“…The extent of the electronic coupling in through-space charge transfer chromophores is affected by the spatial alignment of donor and acceptor aromatic ring systems, and face-to-face configuration leads to a much stronger coupling than edge-to-face arrangement. 38 As evident by the obtained X-ray (Fig. 2) and DFT-optimized structures, the dihedral angle between Cbz and Dipp planes (γ) becomes substantially smaller, if MeCbz ligand is present (in 3 and 4) due to the sterical strain induced bending of the carbazolide plane.…”

π‐Stacked Donor–Acceptor Dendrimers for Highly Efficient White Electroluminescence

“…Here hexaphenylbenzene (HPB) is selected as skeleton because of its nonplanar propeller configuration where six peripheral phenyl rings are perpendicular to the central phenyl ring but are meanwhile facing to each other, providing adesired prototype to anchor six attached aromatic units with spatial interactions. [42] Meanwhile,9 ,9,9',9',9'',9''-hexamethyl-teracridan (TAc) is chosen as peripheral dendron because of its electron-donating nature and dendritic structure to force the outer acridan segments approaching to neighboring acceptors.M oreover,t he orthogonal configuration of TAc where two outer acridan segments are perpendicular to the inner one, [29] allows to control orientation of donors relative to acceptors.T riazine is used as acceptor owing to its electronaccepting ability and planar structure favorable for spatial pp interaction with adjacent donors.T ot une emission color, three dendrimers (BD-Cy,Y D-TF and RD-2TF,F igure 1b) are designed by changing the substituents on triazine acceptors to tune CT strength. Forblue emission (BD-Cy), triazine bearing saturated cyclohexyl group is used as acceptor to decrease the electron-accepting ability.W hile for longer- Angewandte Chemie wavelength emission (YD-TF and RD-2TF), triazine acceptors containing different number of trifluoromethyl groups on phenyl rings are selected.…”

π‐Stacked Donor–Acceptor Dendrimers for Highly Efficient White Electroluminescence

“…Here hexaphenylbenzene (HPB) is selected as skeleton because of its nonplanar propeller configuration where six peripheral phenyl rings are perpendicular to the central phenyl ring but are meanwhile facing to each other, providing adesired prototype to anchor six attached aromatic units with spatial interactions. [42] Meanwhile,9 ,9,9',9',9'',9''-hexamethyl-teracridan (TAc) is chosen as peripheral dendron because of its electron-donating nature and dendritic structure to force the outer acridan segments approaching to neighboring acceptors.M oreover,t he orthogonal configuration of TAc where two outer acridan segments are perpendicular to the inner one, [29] allows to control orientation of donors relative to acceptors.T riazine is used as acceptor owing to its electronaccepting ability and planar structure favorable for spatial pp interaction with adjacent donors.T ot une emission color, three dendrimers (BD-Cy,Y D-TF and RD-2TF,F igure 1b) are designed by changing the substituents on triazine acceptors to tune CT strength. Forblue emission (BD-Cy), triazine bearing saturated cyclohexyl group is used as acceptor to decrease the electron-accepting ability.W hile for longer-…”

“…So far, p-stacked TADF emitters are focused on two kinds of donor-acceptor systems.One is p-stacked small molecules where donor and acceptor are anchored to ar igid molecular skeleton in cofacial alignment pattern, while the other is pstacked polymers in which the donor and acceptor are stacked in side chain of non-conjugated polymer backbone. [10,[26][27][28][29][30] The former have absolute molecular weight and well-defined chemical structure,but are dominated by vacuum deposition in fabrication of organic light-emitting diodes (OLEDs). In contrast, the latter can be processed by solution processes that are compatible with low-cost, large-area fabrication processes,h owever, are suffering from wide molecular-weight distribution and end-group defects which could impair the batch-to-batch repeatability.…”