Modulating Backbone Conjugation of Polymeric Thermally Activated Delayed Fluorescence Emitters for High‐Efficiency Blue OLEDs

Tong, Xingwen; Zhao, Zhennan; Hua, Lei; Zhang, Yuzhuo; Xu, Bowei; Liu, Yuchao; Yan, Shouke; Ren, Zhongjie

doi:10.1002/adfm.202305324

Cited by 14 publications

(6 citation statements)

References 50 publications

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“…As illustrated in Figure b, the EL peaks of p-PXZ-XN-Py and p-PXZ-XN-Pm doped films recorded at the EQE max are 568 and 572 nm, respectively, located in the yellow region. Compared with the PL spectra, the EL spectra of the doped films with the same doping concentration display a redshift, which is attributed to the different emission mechanism . According to the curves of current density–voltage–luminance ( J–V–L ) in Figure c, both p-PXZ-XN-Py and p-PXZ-XN-Pm exhibit a low turn-on voltage of 2.9 V, which benefits from the excellent matching of the HOMO and LUMO energy levels of the functional layers .…”

Section: Results and Discussionmentioning

confidence: 97%

Modulating the Excited States of Thermally Activated Delayed Fluorescence Conjugated Polymers by Introducing Hydrogen Bonding into the Acceptor for High-Performance OLEDs

Guo,

Hua,

Zhao

et al. 2024

J. Phys. Chem. C

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Constructing high-performance thermally activated delayed fluorescence (TADF)-conjugated polymers for solutionprocessed OLEDs is still challenging. Rationally tuning the acceptors has been proven to be an effective way. Therefore, we incorporate pyridine and pyrimidine into the acceptor of conjugated TADF polymers to not only adjust the electronwithdrawing ability of acceptors but also induce the intramolecular hydrogen bonds. Moreover, the excited states of the new synthesized polymers, p-PXZ-XN-Py and p-PXZ-XN-Pm, are also optimized due to the modulated acceptor. Both polymers show the enhanced spin orbital coupling effect and thereby high reverse intersystem crossing rates. Additionally, the construction of intramolecular hydrogen bonds in the acceptors significantly restricts molecular relaxation and thus reduces the nonradiative transition rates of both polymers. Consequently, the EQE max values of p-PXZ-XN-Py and p-PXZ-XN-Pm based OLEDs are promoted to 20.5% at 568 nm and 20.4% at 572 nm, respectively, which rank the first tier among the reported TADF-conjugated polymers with wavelength over 560 nm. Furthermore, they simultaneously maintain a low turn-on voltage of 2.9 V, a low efficiency roll-off of about 12.0% at 500 cd m −2 , and a high brightness approaching 10,000 cd m −2 . Therefore, this work provides a new perspective of acceptor modulation for the construction of highperformance TADF-conjugated polymers.

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Section: Results and Discussionmentioning

confidence: 97%

Modulating the Excited States of Thermally Activated Delayed Fluorescence Conjugated Polymers by Introducing Hydrogen Bonding into the Acceptor for High-Performance OLEDs

Guo,

Hua,

Zhao

et al. 2024

J. Phys. Chem. C

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“…The high k r values of the chiral conjugated polymers were conducive to inhibiting emissive state aggregation and thus preventing exciton quenching. [ 20 ]…”

Section: Resultsmentioning

confidence: 99%

Acceptor Copolymerized Axially Chiral Conjugated Polymers with TADF Properties for Efficient Circularly Polarized Electroluminescence

Zhao,

Tan,

Guo

et al. 2024

Advanced Science

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Chiral conjugated polymer has promoted the development of the efficient circularly polarized electroluminescence (CPEL) device, nevertheless, it remains a challenge to develop chiral polymers with high electroluminescence performance. Herein, by the acceptor copolymerization of axially chiral biphenyl emitting skeleton and benzophenone, a pair of axially chiral conjugated polymers namely R‐PAC and S‐PAC are synthesized. The target polymers exhibit obvious thermally activated delayed fluorescence (TADF) activities with high photoluminescence quantum yields of 81%. Moreover, the chiral polymers display significant circularly polarized luminescence features, with luminescence dissymmetry factor (|glum|) of nearly 3 × 10−3. By using the chiral polymers as emitters, the corresponding circularly polarized organic light‐emitting diodes (CP‐OLEDs) exhibit efficient CPEL signals with electroluminescence dissymmetry factor |gEL| of 3.4 × 10−3 and high maximum external quantum efficiency (EQEmax) of 17.8%. Notably, considering both EQEmax and |gEL| comprehensively, the device performance of R‐PAC and S‐PAC is the best among all the reported CP‐OLEDs with chiral conjugated polymers as emitters. This work provides a facile approach to constructing chiral conjugated TADF polymers and discloses the potential of axially chiral conjugated luminescent skeletons in architecting high‐performance CP‐OLEDs.

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“…As a critical building block for large-area and low-cost flexible display, polymer-based light-emitting diodes (PLEDs) have generated intense attention. − In contrast with traditional PLEDs adopting low-efficiency fluorescent polymers or noble-metal-based phosphorescent polymers as emitters, purely organic thermally activated delayed fluorescence (TADF) polymers allow for 100% internal quantum efficiency by integrally harnessing singlet and triplet excitons, in which the triplet excitons can upconvert to an emissive state via a reverse intersystem crossing (RISC) process. − Especially for TADF conjugated polymers, intrinsic delocalized backbones provide ideal electrical channels for rapidly delivering carriers and subsequently sufficiently generating excitons. Therefore, a high-efficiency TADF conjugated polymer-based electroluminescent (EL) device can be achieved by accurately modulating the composition of conjugated skeletons and TADF segments to make the most possible use of carriers and excitons. − …”

Section: Introductionmentioning

confidence: 99%

“…For example, Tong et al proposed a strategy of local conjugation to construct high-efficiency blue-emitting conjugated polymers, in which the conjugation degree of polymeric backbones can be adjusted by inserting different spacers. Therefore, the energy level of the triplet state and the energy transfer direction of the polymeric main chains can be effectively regulated . Zhao et al improved light-emitting performances through adjusting the local electronegativity of the polymeric backbones by inserting electron-withdrawing atoms and activating energy transmission channels.…”

Section: Introductionmentioning

confidence: 99%

Intramolecular Sensitization Assisting High-Efficiency TADF Conjugated Polymers with Accelerating Exciton Spin Flip for Solution-Processed Electroluminescent Devices

Li,

Xie,

Yin

et al. 2024

Macromolecules

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Thermally activated delayed fluorescence (TADF) conjugated polymers have attracted a lot of attention for their potential to produce flexible display devices. However, insufficient energy transfer from the host to TADF units will result in exciton− exciton annihilation and reduced device efficiency. To address these problems, an intramolecular sensitization strategy is employed in this work in which the spin flip of a triplet exciton can be accelerated by the intermediation of TADF sensitization units in polymers. By regulating the ratio of each polymeric component, excellent photophysical properties can be achieved with a photoluminescence quantum yield of 86% and a high rate of reverse intersystem crossing of 6.3 × 10 5 s −1 . Moreover, the solution-processed polymer-based organic light-emitting diodes can achieve an attractive external quantum efficiency of 21.02% due to the effective utilization of triplet excitons. Overall, this research validates the feasibility of an intramolecular sensitization strategy for restraining exciton annihilation, thus providing a promising pathway for designing high-performance conjugated TADF polymers.

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Modulating Backbone Conjugation of Polymeric Thermally Activated Delayed Fluorescence Emitters for High‐Efficiency Blue OLEDs

Cited by 14 publications

References 50 publications

Modulating the Excited States of Thermally Activated Delayed Fluorescence Conjugated Polymers by Introducing Hydrogen Bonding into the Acceptor for High-Performance OLEDs

Modulating the Excited States of Thermally Activated Delayed Fluorescence Conjugated Polymers by Introducing Hydrogen Bonding into the Acceptor for High-Performance OLEDs

Acceptor Copolymerized Axially Chiral Conjugated Polymers with TADF Properties for Efficient Circularly Polarized Electroluminescence

Intramolecular Sensitization Assisting High-Efficiency TADF Conjugated Polymers with Accelerating Exciton Spin Flip for Solution-Processed Electroluminescent Devices

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