Thermally activated delayed fluorescence dendrimers with exciplex-forming dendrons for low-voltage-driving and power-efficient solution-processed OLEDs

Sun, Kaiyong; Sun, Yuting; Tian, Wenwen; Liú, Dan; Feng, Yingli; Sun, Yueming; Jiang, Wei

doi:10.1039/c7tc04720g

Cited by 45 publications

(23 citation statements)

References 39 publications

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“…For example, fluorescent conjugated donor–acceptor polymers with CT emission (for example, polyfluorene and polyspirofluorene derivatives) have been a successful strategy to realize full‐color solution‐processed organic light‐emitting diodes (OLEDs) with emission covering the whole visible region. Recently, thermally activated delayed fluorescence (TADF) polymers with finely controlled CT processes have attracted much attention because they can utilize non‐emissive triplet excitons through reverse intersystem crossing (RISC) process to realize 100 % internal quantum efficiency (IQE) . Regardless of their structures (main‐chain, side‐chain, and dendritic structures), TADF polymers are mainly designed by introducing conjugated donor–acceptor chromophores into the main chain or side chain of polymers.…”

Section: Figurementioning

confidence: 99%

Developing Through‐Space Charge Transfer Polymers as a General Approach to Realize Full‐Color and White Emission with Thermally Activated Delayed Fluorescence

et al. 2019

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Through‐space charge transfer polymers (TSCT polymers) that contain a non‐conjugated polystyrene backbone and spatially separated donor and acceptor units for solution‐processed OLEDs with full‐color and white emission is reported. By tuning the charge transfer strength between donor and acceptors with different electron‐accepting ability, emission color spanning from deep blue to red can be achieved. By incorporating two kinds of donor/acceptor pairs in one polymer to create duplex through‐space charge‐transfer channels, blue and yellow emission can be simultaneously obtained to realize white electroluminescence from a single polymer. The TSCT polymers exhibit thermally activated delayed fluorescence effect with delayed‐component lifetimes in range of 0.36–1.98 μs, and unexpected aggregation‐induced emission (emission intensity enhancement of up to 117 from solution to aggregation state).

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Section: Figurementioning

confidence: 99%

Developing Through‐Space Charge Transfer Polymers as a General Approach to Realize Full‐Color and White Emission with Thermally Activated Delayed Fluorescence

et al. 2019

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“…TADF dendrimers with different peripheral ends were compared in the TADF emitters G‐TCTA and G‐mCP ( Figure ). 4,4′,4′′‐Tri(9‐carbazoyl) triphenylamine ( TCTA) and 9,9′‐(1,3‐phenylene)bis‐9 H ‐carbazole (mCP) were selected as the outer dendrons for TADF dendrimers due to their high triplet levels . They can also form an interfacial exciplex between the interface of outer dendrons and the ETL layer of 4,6‐bis(3,5‐di(pyridin‐3‐yl)phenyl)‐2‐methylpyrimidine ( B3PYMPM ) as an additional emission path.…”

Section: Tadf Polymersmentioning

confidence: 99%

“…For G‐mCP , a high PLQY of 90% can be obtained while for G‐TCTA only a very low PLQY of 0.08 can be reached, explained by the formation of intramolecular exciplex between the TCTA dendron and the emissive core G‐G0 . Solution‐processed non‐doped green‐emitting OLEDs with a configuration of ITO/PEDOT:PSS (40 nm)/ G‐mCP (40 nm)/B3PYMPM (55 nm)/Cs 2 CO 3 (1 nm)/Al (100 nm) were fabricated and exhibited an exceptional high maximum EQE of 16.5% . Recently, a bipolar phosphine oxide carbazole moiety was prepared as dendron, which was linked to the emissive core of the bis[4‐(3,6‐dimethoxycarbazole)phenyl] sulfone ( DMOC‐DPS ) by alkyl linker to prepare the dendrimer POCz‐DPS ( Figure ).…”

Section: Tadf Polymersmentioning

confidence: 99%

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

Wei

Voit

2018

Macromol. Rapid Commun.

117

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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“…This work, by combining the two parallel emissive channels, provided a novel and efficient design strategy for non-doped solution-processed TADF emitters. Sun et al (2018) designed and synthesized two new dendrimers (G-TCTA and G-mCP, see Figure 4), which had effective non-conjugated connections between TADF core (G-G0) and different excited complex dendrites. The dendrimer G-mCP exhibited a smaller E ST (0.08 eV) and a higher PLQY (90%).…”

Section: High Molecular Weight Tadf Dendrimermentioning

confidence: 99%

Recent Advances in Thermally Activated Delayed Fluorescent Polymer—Molecular Designing Strategies

Yin

Wang

et al. 2020

Front. Chem.

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Thermally activated delayed fluorescent (TADF) materials, as the third generation of organic electroluminescent materials, have many advantages over other organic light-emitting diodes (OLEDs) materials, such as 100% internal quantum efficiency, no doping of heavy metals, and avoiding the shortages of ordinary fluorescent materials and phosphorescent materials. So it is considered to be the most competitive organic light-emitting materials, and has great application prospects in the field of OLEDs. So far, small-molecule TADF materials have achieved high quantum yield and full-color range of red, green, and blue. However, TADF polymers suitable for low-cost and easily scalable solution processing are less developed, which are confined by the preparation methods and polymers designing, and there are still challenges of increasing quantum efficiency and strengthening device performance. This review mainly summarizes different synthesis strategies of TADF polymers and the latest development in the field. Special attention is focused on illustrating the designing and structure-property relationship of TADF polymers, and finally, an outlook is given for the design and application prospect of TADF polymers in the future.

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Thermally activated delayed fluorescence dendrimers with exciplex-forming dendrons for low-voltage-driving and power-efficient solution-processed OLEDs

Abstract: To realize power efficient nondoped solution-processed OLEDs, a novel strategy of constructing a TADF dendrimer with the characteristic of exciplex-forming dendrons has been presented.

Cited by 45 publications

References 39 publications

Developing Through‐Space Charge Transfer Polymers as a General Approach to Realize Full‐Color and White Emission with Thermally Activated Delayed Fluorescence

Developing Through‐Space Charge Transfer Polymers as a General Approach to Realize Full‐Color and White Emission with Thermally Activated Delayed Fluorescence

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

Recent Advances in Thermally Activated Delayed Fluorescent Polymer—Molecular Designing Strategies

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