Pioneering research on blue “hot exciton” polymers and their application in solution-processed organic light-emitting diodes

Zhang, J.Q.; Li, Wei; Lyu, Lingling; Wei, Qiang; Meng, Yuanyuan; Li, Deli; Wang, Zhichuan; Luo, Ming; Du, Songyu; Xu, Jiang; Zhang, Xiao Li; Xie, Guohua; Ge, Ziyi

doi:10.1039/d3mh00676j

Cited by 6 publications

(2 citation statements)

References 31 publications

(32 reference statements)

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“…The binding energies were calculated to be 6.63 for the Z-isomer and 9.43 kcal/mol for the E-isomer, indicating that the E-isomer formed a more tightly packed molecular structure, whereas Z-isomers exhibited much looser packing units. Furthermore, compounds Cz-An-TPE-Cz with a single anthracene and 2Cz-TPE (previous work), [36] which lacks the anthracene unit (Scheme S4), were synthesized for comparison. Notably, neither of these materials exhibited the DE phenomenon (Figure S11a).…”

Section: Theoretical Calculation and Analysismentioning

confidence: 99%

AIEgen configuration transition and aggregation enable dual prompt emission for single‐component nondoped white OLEDs

Zhang,

Wei,

et al. 2023

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The dual emission (DE) feature in materials holds great potential to revolutionize the development of one‐component system white organic light‐emitting diodes (WOLEDs). However, the reported DE materials remain scarce owing to the formidable challenge of breaking Kasha's rule and managing the intricate energy/charge transfer processes. Herein, we have introduced a groundbreaking DE AIEgen, 2CzAn‐TPE, which possesses a simple structure and undergoes Z‐to‐E isomerization and exhibits yellow and red fluorescence powders for pre‐ and post‐sublimation, respectively. With relatively lower potential energy, Z‐conformation ((Z)‐1,2‐diphenyl‐1,2‐bis(4‐(10‐(9‐phenyl‐9H‐carbazol‐3‐yl)anthracen‐9‐yl)phenyl)ethene) of 2CzAn‐TPE can be readily transformed into E‐conformation ((E)‐1,2‐diphenyl‐1,2‐bis(4‐(10‐(9‐phenyl‐9H‐carbazol‐3‐yl)anthracen‐9‐yl)phenyl)ethene) via vacuum sublimation. The utilization of X‐ray diffraction and grazing‐incidence‐wide‐angle X‐ray scattering techniques confirms the structural transformation, while the crystallographic analysis reveals the establishment of numerous intermolecular CH···π interactions between the tetraphenylethene (TPE) moiety and both the anthracene and carbazole units. This allows a densely packed molecular arrangement, thereby offering propitious conditions for excimer generation in the E‐conformation aggregated state. By utilizing the sublimated 2CzAn‐TPE as an emitter, a nondoped one‐component WOLED was prepared, exhibiting an exceptionally high external quantum efficiency (EQE) of 5.0%, which represents one of the highest performances among all one‐component WOLEDs. This research introduces a novel, simple, and efficient approach to realize highly efficient one‐molecule WOLEDs.

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Section: Theoretical Calculation and Analysismentioning

confidence: 99%

AIEgen configuration transition and aggregation enable dual prompt emission for single‐component nondoped white OLEDs

Zhang,

Wei,

et al. 2023

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“…To gain further insights into the transition characteristics of triplet excitons, femtosecond transient absorption spectroscopy (TAS) was carried out using a pump wavelength of 400 nm, and the materials were dissolved in toluene (10 −4 m ). [ 45,46 ] As depicted in Figure 3c, all the samples demonstrated comparable photo‐induced absorption properties spanning from 360 to 760 nm. The relatively light blue absorption band observed between 360 and 420 nm can be attributed to the absorption of singlet excitedstate levels, while the dark purple absorption band observed between 550 and 700 nm corresponds to the triplet excited state levels.…”

Section: Resultsmentioning

confidence: 92%

Cooperative Passivation Exciton Quenching Triggers Surpassing 30% External Quantum Efficiency for a Deep‐Blue Organic Light‐Emitting Diode

Zhang,

Li,

et al. 2023

Laser & Photonics Reviews

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Overcoming exciton quenching and improving electroluminescence (EL) performances continue to pose persistent challenges in the development of efficient deep blue thermally activated delayed fluorescence (TADF) emitters. Herein, an asymmetric multi‐donors strategy is employed that provides the potential of establishing multiple radiative transition channels for fluorescence emission and reverse intersystem crossing (RISC), while allowing flexible modulation of packing modes in single‐crystal state and optimization of morphology in films by modifying the substitution site of the donor units. As a result, intermolecular π–π interactions are effectively alleviated and a very smooth surface with a reduced defect density is simultaneously achieved, which can significantly reduce the density of triplet excitons, accelerate the charge transfer rate, and enhance carrier injection efficiency. Consequently, a super‐high photoluminescence quantum yield (PLQY) of 99% and fast kRISC of 1.1 × 105 s−1 are concurrently achieved for the proof‐of‐concept emitter 3,4‐Cz‐SF‐SFAC. The corresponding deep‐blue organic light‐emitting diode (OLED) demonstrates an exceptional external quantum efficiency (EQE) of 31.1%, accompanied by an emission peak at 457 nm, one of the preeminent TADF materials within the deep blue region, ranking among the most efficient OLEDs with an EL spectra below 460 nm on record.

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A Hot Exciton Luminogen Constructed by an o‐Carborane Scaffold

Yu,

Xu,

Wang

et al. 2024

Advanced Optical Materials

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Emitters with the combination of an electron donor (D) and an acceptor (A) have been widely studied and usually exhibited interesting photophysical properties. Hot exciton materials involving an ordinary D‐A structure typically undergo a hybridized local charge transfer (HLCT) process. However, the hot exciton molecules containing more D/A fragments are much less explored. In this study, a new hot exciton material based on an inorganic boron cluster is designed and synthesized, which possesses a V‐type D–A–A′–D′ molecular architecture. The emitter shows an impressive photoluminescence quantum yield (PLQY) of up to 90% and demonstrates multiple emissions, excitation‐wavelength‐, solvent‐, and temperature‐dependent emissions. These characteristics are attributed to the coexistence of HLCT and the through‐space charge transfer process (TSTC) triggered by an o‐carborane scaffold in the excited state. Besides, the interchangeable HLCT/TSCT/hRISC processes are demonstrated by temperature‐dependent spectra and femtosecond time‐resolved transient absorption spectra. These findings confirm a novel hot exciton mechanism, simultaneously induced by HLCT and TSCT. This is also the first example of a carborane‐based hot exciton molecule. The current study not only reports a new molecular architecture for a hot exciton material but also gives rise to a new insight into the hot exciton mechanism.

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Pioneering research on blue “hot exciton” polymers and their application in solution-processed organic light-emitting diodes

Abstract: An innovative novel category of polymeric hybridized local and charge-transfer (HLCT) blue materials prepared via solution processing has yet to be reported. This study introduces three polymers, namely PZ1, PZ2,...

Cited by 6 publications

References 31 publications

AIEgen configuration transition and aggregation enable dual prompt emission for single‐component nondoped white OLEDs

AIEgen configuration transition and aggregation enable dual prompt emission for single‐component nondoped white OLEDs

Cooperative Passivation Exciton Quenching Triggers Surpassing 30% External Quantum Efficiency for a Deep‐Blue Organic Light‐Emitting Diode

A Hot Exciton Luminogen Constructed by an o‐Carborane Scaffold

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