Backbone‐Acceptor/Pendant‐Donor Strategy for Efficient Thermally Activated Delayed Fluorescence Conjugated Polymers with External Quantum Efficiency Close to 25% and Emission Peak at 608 nm

Abstract

(2 of 10)www.advopticalmat.de Scheme 1. Strategies for constructing TADF small molecules and polymers. TADF small molecules: a) redshifted emission with extended conjugation of acceptor. TADF polymers: b) In our previous work, the polymers with BDPA architecture achieve green and yellow emissions with excellent EL performances; c) In this work, the polymers with BAPD architecture are expected to produce a relatively redshifted emission such as orange to red emissions, based on extensively conjugated acceptor backbone.

Design, synthesis, and properties of polystyrene‐based through‐space charge transfer polymers: Effect of triplet energy level of electron donor moiety on delayed fluorescence and electroluminescence performance

“…The introduction of donor and acceptor into conjugated polymer backbone not only allows to tune emission color by adjusting the donor and acceptor strength, but also can regulate energy levels of excited state to realize efficient exciton utilization. However, the strong electron coupling mediated by covalent bonds in TBCT polymers tends to induce considerable redshift of emission, undesirable for blue/deep blue emission 3,4,18,33 . Meanwhile, singlet‐triplet energy splitting (∆E ST ) of TBCT polymers can be increased by strong electron interaction between donor and acceptor, which is unfavorable for achieving TADF effect 1 …”

“…However, the strong electron coupling mediated by covalent bonds in TBCT polymers tends to induce considerable redshift of emission, undesirable for blue/deep blue emission. 3,4,18,33 Meanwhile, singlet-triplet energy splitting (ΔE ST ) of TBCT polymers can be increased by strong electron interaction between donor and acceptor, which is unfavorable for achieving TADF effect. 1 Different from TADF polymers with π-conjugated D-A structure and TBCT emission, TADF polymers with π-stacked D-A architectures and through-space charge transfer (TSCT) emission have been reported by our group to realize blue TADF emission.…”

Thermally Activated Delayed Fluorescent (TADF) Mono‐Polymeric OLED with Higher EQE over Its TADF Repeating Unit

“…[12][13][14] Till now, the reported emission color of small molecular TADF materials have covered the whole visible range. [15][16][17][18][19] Donoracceptor structure with torsion angle of donor (D) and acceptor (A) moieties was usually resorted to design TADF smallmolecules, which can achieve effective separation of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), much favored for small singlet-triplet energy splitting (ΔE st ) to the process of RISC. [20][21][22][23][24] However, small-molecule materials always feature poor solubility resulting from easily crystallization, and thus, they were mostly fabricated by thermal evaporation technique in vacuum.…”

Narrowband Emissive TADF Conjugated Polymers towards Highly Efficient Solution‐Processible OLEDs

“…Benefitting from the advantages of good film-forming stability, cost-effectiveness and suitability for large-area production, thermally activated delayed fluorescence (TADF) polymers have attracted great attention in the field of organic light-emitting diode (OLED) towards future solid lighting and displays. [1][2][3][4] Up to date, the development of TADF polymers has made great progress, accompanying with excellent electroluminescence (EL) performances with maximum external quantum efficiencies (EQEs) of over 20 % for green, [5][6][7] yellow [8,9] and white [10] OLEDs. However, TADF polymers with high color purity are rarely reported, due to their intrinsic broad emission spectra.…”

“…Compared to the non-conjugated TADF polymers, conjugated TADF polymers usually demonstrate better charge transport capability because of extended conjugation along the polymeric backbone, which is conducive to obtain better EL performance. [8] However, conjugated TADF polymers usually exhibit red-shifted and broadened emissions due to the inevitable CT effect and conjugation elongation along backbone. For example, as depicted in Scheme 1, based on the backbone-donor/pendant-acceptor (for polymer PABPCx [30] ), and the backbone-acceptor/ pendant-donor (for polymer PSAQFx [8] ) structures, large red-shifts in the photoluminescence (PL) spectra with values of 65 and 40 nm were observed for PABPCx and PSAQFx polymers, respectively, relative to their TADF chromophores.…”