Inheriting the Characteristics of TADF Small Molecule by Side‐Chain Engineering Strategy to Enable Bluish‐Green Polymers with High PLQYs up to 74% and External Quantum Efficiency over 16% in Light‐Emitting Diodes

Xie, Guohua; Luo, Jiajia; Huang, Manli; Chen, Tianheng; Wu, Kailong; Gong, Shaolong; Yang, Chuluo

doi:10.1002/adma.201604223

Cited by 212 publications

(118 citation statements)

References 36 publications

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“…With the increase of the TADF units in the copolymer, the emission of the polycarbazole ( PCzDP‐n ) decreased significantly, which suggested efficient energy transfer from the main chain to the TADF unit, and all these polymers exhibited high PLQY of up to 74% in the film. By utilizing the TADF polymeric emitters in solution‐processed OLED devices with the structure of ITO/PEDOT:PSS (50 nm)/emitting layer (EML) (70 nm)/TmPyPB (40 nm)/Liq (1 nm)/Al (100 nm), a significantly higher maximum EQE of 16.1% of bluish‐green emission could be obtained proving this as a very valid design concept …”

Section: Tadf Polymersmentioning

confidence: 96%

“…In further research, the authors refined this concept by using the TADF D–A monomer 10‐(4‐((4‐(3,6‐dibromo‐9H‐carbazol‐9‐yl)phenyl)sulfonyl)phenyl)‐10 H ‐phenoxazine ( PXZ‐DP‐BrCz ) together with other two non‐TADF comonomers ( Figure ) . As derived from density functional theory (DFT) calculation, the LUMOs of the resulting copolymer are mainly located on the diphenyl sulfone moiety, while the HOMOs are located at the electron donor of phenoxazine, exhibiting electronic separation from the main chain of polycarbazole.…”

Section: Tadf Polymersmentioning

confidence: 99%

See 1 more Smart Citation

Thermally Activated Delayed Fluorescent Polymers: Structures, Properties, and Applications in OLED Devices

Wei

Voit

2018

Macromol. Rapid Commun.

122

100

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several organic layers like hole injection layer, hole-and electron transport layer, and most importantly, the emissive layers (EML), inserted between the electrodes (Figure 1). Under external voltage, opposite charge carriers of holes and electrons are injected from anode and cathode and finally recombined to produce photons within the EML. [10][11][12] Emitters can largely determine not only the performance but also the processing methods of devices, and therefore they are the key material among all the components of the OLEDs. During the past three decades, the emitter materials have seen a rapid progress, from traditional fluorescent, phosphorescent, and triplet-triplet annihilation (TTA) materials into the era of thermally activated delayed fluorescent (TADF) materials, and from small molecules to polymers. [13] According to spin statistics, singlet and triplet excitons are formed within the EML at the ratio of 1:3, when OLED devices are working under electrical excitation; however, the organic emitters have different capabilities to utilize the exciton to induce photons which results in different efficiencies of OLED devices. The electricity-photon conversion efficiency of OLED can be evaluated by the quantum efficiency (QE), referring to the numeral ratio of photons to the injected electronhole pairs. [14,15] QE can be further subdivided into internal quantum efficiency (IQE) and external quantum efficiency (EQE). The IQE, defined as photon generation within the EML, is directly determined by the emitters, [16] while EQE refers to the numerical ratio of total photons emitting out of the device to the charge pairs injected. Since the photons are generated within and emitted out from the EML, the chemical structure of the emitter and the resulting properties can deeply influence the device efficiency. The traditional fluorescent emitters can only take advantages of singlet excitons for luminescence, with maximal IQE of roughly 25%. Given that out-coupling efficiency is normally 20%, the maximal EQE is only 5%, far below expectation. Phosphorescent OLEDs have the capability to reach 100% IQE, because phosphorescent emitters usually contain heavy atoms like iridium or platinum to harvest both, singlet and triplet excitons for phosphorescence through significant spin-orbit coupling, but the heavy metals usually bring about serious issues of comparable high costs and low long-term stability in OLEDs. [17] TTA fluorescent emitters can only reach a maximum IQE of 62.5% through conversion of two triplet excitons into one singlet exciton, and show mainly blue emission. [18] TADF materials, however, can harvest triplet Organic Light-Emitting Diodes Thermally activated delayed fluorescent (TADF) polymers are promising emitting materials to realize highly efficient, large-scale, and low-cost organic light-emitting diodes (OLEDs) since they exhibit various advantages such as heavy-metal-free structures, 100% theoretical internal quantum efficiency, and ease of large-area fabrication through solution process. At present,...

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Section: Tadf Polymersmentioning

confidence: 96%

Section: Tadf Polymersmentioning

confidence: 99%

Thermally Activated Delayed Fluorescent Polymers: Structures, Properties, and Applications in OLED Devices

Wei

Voit

2018

Macromol. Rapid Commun.

122

100

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show abstract

“…Polymers, in contrast, can have both good thermal stability, solution processable and facile functionality to introduction of various functional units into pendant groups . Nowadays, polymeric materials have been proven to be ideal emissive materials for the solution‐processed devices .…”

Section: Introductionmentioning

confidence: 99%

Solution‐Processable Thermally Activated Delayed Fluorescence White OLEDs Based on Dual‐Emission Polymers with Tunable Emission Colors and Aggregation‐Enhanced Emission Properties

Nobuyasu

Wang

et al. 2017

Advanced Optical Materials

102

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Thermally activated delayed fluorescence (TADF) white organic light‐emitting diodes (WOLEDs) have drawn tremendous interest and have been extensively studied because of harvesting both triplet and singlet excitons without heavy metals. However, single white‐light‐emitting polymers are currently limited and few strategies exist to design these materials. Herein, a new strategy is proposed to develop the polymers with tunable emission colors by combining fluorescence and TADF based on aggregation‐enhanced emission (AEE) characteristics. The polymers containing different ratios of pendant 2‐(10H‐phenothiazin‐10‐yl)dibenzothiophene‐S,S‐dioxide units with yellow TADF emission and dibenzothiophene units with blue fluorophor emission, which display both TADF and AEE characteristics, are synthesized successfully. Among them, the emission color of P3 in different tetrahydrofuran/water mixtures changes from greenish‐blue to white or yellow. Moreover, P3 displays white emission in the solid state dispersing by poly(methyl methacrylate). In addition, electroluminescent device of P3 achieve white light emission with high color rending indexes (CRI) and low turn‐on voltages (V on ). P3 OLEDs show two‐color warm‐white emission with high CRI of 77, low V on of 2.9 V, CEmax of 23.0 cd A−1, PEmax of 32.8 lm W−1, external quantum efficiency (EQE)max of 10.4% with Commission Internationale de l'Eclairage coordinates of (0.37, 0.38) at 5 V. Moreover, EQE of 2.6%, CE of 5.7 cd/A, PE of 4.7 lm W−1 at 100 cd m−2 are obtained. To the best of our knowledge, this work reports the first example of warm‐white TADF polymer OLEDs.

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“…77 Intuitively, TADF polymers should be based on a non-conjugated backbone to prevent triplet trap formation as triplet energy has been known to decrease rapidly with increasing effective conjugation length. 79,82 However, there have been several reports of conjugated TADF polymers with chromophores either grafted 83,84 or built-in along the polymer main-chain [85][86][87], and most of them performed nicely in PLED devices (EQE: 2.2-16.1%). Wei et al recently demonstrated how a TADF-inactive carbazole-based monomer could be turned into a TADF-active macromolecule (macrocycle or polymer).…”

Section: Thermally Activated Delayed Fluorescence (Tadf) Polymersmentioning

confidence: 99%

“…118 On the other hand, the best non-conjugated TADF polymer (TADF-P2) offered a green PLED (k EL at 533 nm) with an EQE of 20.1% 21, whereas the conjugated counterpart (PCzDP-10) gave a PLED with a blue emission at 496 nm and an EQE of 16.1%. 83 Therefore, it is reasonable to conclude that for these two classes of polymers (phosphorescent and TADF), the nature of the polymer backbone has minimal impact on the PLED performance.…”

Section: Conjugated Versus Non-conjugated Polymers: Pled Performancesmentioning

confidence: 99%

Recent Advances in Polymer Organic Light-Emitting Diodes (PLED) Using Non-conjugated Polymers as the Emitting Layer and Contrasting Them with Conjugated Counterparts

Wong

2017

Journal of Elec Materi

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Polymer organic light-emitting diodes (PLED) are one of the most studied subjects in flexible electronics thanks to their economical wet fabrication procedure for enhanced price advantage of the product device. In order to optimize PLED efficiency, correlating the polymer structure with the device performance is essential. An important question for the researchers in this field is whether the polymer backbone is conjugated or not as it affects the device performance. In this review, recent advances in non-conjugated polymers employed as the emitting layer in PLED devices are first discussed, followed by their contrast with the conjugated counterparts in terms of polymer synthesis, sample quality, physical properties and device performances. Such comparison between conjugated and non-conjugated polymers for PLED applications is rarely attempted, and; hence, this review shall provide a useful insight of emitting polymers employed in PLEDs.

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Inheriting the Characteristics of TADF Small Molecule by Side‐Chain Engineering Strategy to Enable Bluish‐Green Polymers with High PLQYs up to 74% and External Quantum Efficiency over 16% in Light‐Emitting Diodes

Cited by 212 publications

References 36 publications

Thermally Activated Delayed Fluorescent Polymers: Structures, Properties, and Applications in OLED Devices

Thermally Activated Delayed Fluorescent Polymers: Structures, Properties, and Applications in OLED Devices

Solution‐Processable Thermally Activated Delayed Fluorescence White OLEDs Based on Dual‐Emission Polymers with Tunable Emission Colors and Aggregation‐Enhanced Emission Properties

Recent Advances in Polymer Organic Light-Emitting Diodes (PLED) Using Non-conjugated Polymers as the Emitting Layer and Contrasting Them with Conjugated Counterparts

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