Dendronized delayed fluorescence emitters for non-doped, solution-processed organic light-emitting diodes with high efficiency and low efficiency roll-off simultaneously: two parallel emissive channels

Li, Yifan; Xie, Guohua; Gong, Shaolong; Wu, Kailong; Yang, Chuluo

doi:10.1039/c6sc00943c

Cited by 187 publications

(98 citation statements)

References 29 publications

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“…[19][20][21] In summary,w eh ave designed and synthesized efficient blue TADF materials,inwhich charge is transferred through the aryl linker and through space simultaneously.Combining the two charge-transfer pathways allows very small DE ST and enough large transition dipole moment at the same time.The highly twist structures and alkyl substituents of these molecules efficiently inhibit aggressive quenching which are usually caused by intermolecular p-p stacking. Assuming out-coupling efficiencies of 20-30 %f or planar OLEDs,weinfer avery high IQE (63-95 %) for device B.…”

Section: Angewandte Chemiementioning

confidence: 99%

“…To our knowledge,t his is the highest EQE value ever reported for non-doped solution-processed OLEDs based on TADF emitters. [19][20][21] In summary,w eh ave designed and synthesized efficient blue TADF materials,inwhich charge is transferred through the aryl linker and through space simultaneously.Combining the two charge-transfer pathways allows very small DE ST and enough large transition dipole moment at the same time.The highly twist structures and alkyl substituents of these molecules efficiently inhibit aggressive quenching which are usually caused by intermolecular p-p stacking. Non-doped, solution-processed blue OLEDs based on these emitters achieved EQEs of 8% and 19.1 %, respectively.C learly,t he combined charge-transfer pathway represents avery promising new strategy for developing novel and efficient TADF materials.…”

Section: Angewandte Chemiementioning

confidence: 99%

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Combining Charge‐Transfer Pathways to Achieve Unique Thermally Activated Delayed Fluorescence Emitters for High‐Performance Solution‐Processed, Non‐doped Blue OLEDs

et al. 2017

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Two efficient blue thermally activated delayed fluorescence compounds, B-oCz and B-oTC, composed of ortho-donor (D)-acceptor (A) arrangement were designed and synthesized. The significant intramolecular D-A interactions induce a combined charge transfer pathway and thus achieve small ΔE and high efficiencies. The concentration quenching can be effectively inhibited in films of these compounds. The blue non-doped organic light emitting diodes (OLEDs) based on B-oTC prepared from solution processes shows record-high external quantum efficiency (EQE) of 19.1 %.

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Section: Angewandte Chemiementioning

confidence: 99%

Section: Angewandte Chemiementioning

confidence: 99%

Combining Charge‐Transfer Pathways to Achieve Unique Thermally Activated Delayed Fluorescence Emitters for High‐Performance Solution‐Processed, Non‐doped Blue OLEDs

et al. 2017

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“…As shown in Figure 4, m-PXZP and p-PXZP present reversible one-electron oxidation process in CV curves, corresponding to the oxidation process of PXZ unit; whereas o-PXZP display quasi-reversible, double-electron oxidation process because of the asymmetry configuration of two PXZ units. According to the onset voltages of the oxidation curves, [47][48][49] their HOMO levels are determined to be −5. Obtained from the intersection of the normalized absorption spectra; e) Determined by the onset of the oxidation curves; LUMO levels were calculated by using HOMO levels and…”

Section: Electrochemical Propertiesmentioning

confidence: 99%

Tailoring Optoelectronic Properties of Phenanthroline‐Based Thermally Activated Delayed Fluorescence Emitters through Isomer Engineering

Zhang

Zhan

et al. 2016

Advanced Optical Materials

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Three isomeric phenanthroline compounds, namely o-PXZP, m-PXZP, and p-PXZP, are constructed by incorporating electron-donor phenoxazine unit into ortho-, meta-, or para-positions of a rigid electron-acceptor phenanthroline core. This approach functionalizes these compounds to exhibit thermally activated delayed fluorescence (TADF) characteristics with microsecondscale photoluminescence (PL) lifetimes. Their thermal, electrochemical properties, emissive characteristics, and energy levels can be finely tailored through isomer engineering. The meta-and para-linking compounds (m-PXZP and p-PXZP) possess higher decomposition temperatures, deeper lowest unoccupied molecular orbital levels, higher PL quantum efficiencies, smaller singlet-triplet energy splitting, and reduced DF lifetimes relative to their ortho-disposition isomer (o-PXZP). Consequently, a green fluorescence organic light-emitting diode (OLED) based on m-PXZP achieves a maximum external quantum efficiency of 18.9%, and has a slow efficiency roll-off of 28% at the luminance of 1000 cd m −2 . Notably, m-PXZP-based device exhibits a nearly 100% utilization efficiency of electro-generated singlet and triplet excitons. These results demonstrate for the first time that phenanthroline derivatives can be employed as TADF emitters for high-efficiency OLEDs. The isomer engineering for TADF emitters provides a simple method to extend structure diversity of TADF emitters, and moreover it provides a flexible method to optimize optoelectronic properties and thereby manipulate electroluminescence performance.

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“…Similarly, Yang et al. attached two carbazole dendrons onto the TADF emissive core bis(4‐(9,9‐dimethylacridin‐10(9 H )‐l)phenyl)methanone ( DMAC‐BP ) to prepare dendrimers CDE1 and CDE2 ( Figure ) . With increasing generation number of the carbazole dendrons, the PL emission peaks of neat films blue‐shifted, which implies weaker charge transfer (CT) ability of CDE2 than of CDE1 .…”

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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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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Dendronized delayed fluorescence emitters for non-doped, solution-processed organic light-emitting diodes with high efficiency and low efficiency roll-off simultaneously: two parallel emissive channels

Abstract: Carbazole-dendronized TADF emitters enable non-doped, solution-processed OLEDs to achieve a high EQE of 13.8% and a low efficiency roll-off simultaneously.

Cited by 187 publications

References 29 publications

Combining Charge‐Transfer Pathways to Achieve Unique Thermally Activated Delayed Fluorescence Emitters for High‐Performance Solution‐Processed, Non‐doped Blue OLEDs

Combining Charge‐Transfer Pathways to Achieve Unique Thermally Activated Delayed Fluorescence Emitters for High‐Performance Solution‐Processed, Non‐doped Blue OLEDs

Tailoring Optoelectronic Properties of Phenanthroline‐Based Thermally Activated Delayed Fluorescence Emitters through Isomer Engineering

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

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