Multichannel charge transfer enhanced radiative decay and RISC in TADF materials containing multiple donors and acceptors

He, Zhaolong; Li, Jiuyan; Liu, Di; Wan, Huihui; Mei, Yongqiang; Shi, Chunlong

doi:10.1039/d2tc03875g

Cited by 7 publications

(1 citation statement)

References 39 publications

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“…Particularly, the k RISC value for dCF 3 BFCzOXD was over an order of magnitude faster than 32BFCzA, which may be attributed to its smaller Δ E ST and stronger donor‐acceptor electron coupling interaction. [ 26 ] The rates of triplet non‐radiative decay ( k T nrs) were also calculated to be 7.28 × 10 5 , 6.27 × 10 5 and 6.73 × 10 5 s –1 for 32BFCzA, m CF 3 BFCzOXD and dCF 3 BFCzOXD, and the more serious non‐radiative transition for 32BFCzA may also be an inducement to its inefficient up‐conversion process.…”

Section: Resultsmentioning

confidence: 99%

Fine Tuning of Donor‐Acceptor Structures in Fused‐Carbazole Containing Thermally Activated Delayed Fluorescence Materials towards High‐Efficiency OLEDs

Yuan

Wang

et al. 2023

Chin. J. Chem.

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Comprehensive Summary Conjugated fused‐ring structures have attracted extensive attention due to their high molecular rigidity to restrain excited‐state relaxation and non‐radiative decay, and further to enhance the luminance efficiency for emissive materials. Herein, we develop a series of donor‐acceptor type thermally activated delayed fluorescence (TADF) emitters by introducing fused‐ring 5H‐benzofuro[3,2‐c]carbazole (32BFCz) as electron donating unit. Through optimizing the numbers and structure of donor and acceptor moieties, three compounds named 32BFCzA, mCF3BFCzOXD and dCF3BFCzOXD are designed, which are composed by mono‐32BFCz/trifluoromethylpicolinonitrile, penta‐BFCz/3‐(trifluoromethyl)phenyl)‐1,3,4‐oxadiazol‐2‐yl)benzene and penta‐32BFCz/3,5‐bis(trifluoromethyl)phenyl)‐1,3,4‐oxadiazol‐2‐yl)benzene as donor/acceptor groups, respectively. They all exhibited green emission with peak value ranging from 532 to 540 nm. Through rationally tuning the donor/acceptor properties to reduce the distance between positive and negative charges, the ground state dipole moments decline from 8.93, 6.18 to 5.30 Debye, which further induced sequentially reduced singlet‐triplet energy splits (ΔESTs), increased photoluminescence quantum yields (PLQYs), enhanced reverse intersystem crossing rate (kRISCs) and diminished delayed fluorescence lifetime from 32BFCzA, mCF3BFCzOXD to dCF3BFCzOXD. Therefore, gradually increased external quantum efficiency (EQE) is accordingly achieved when employing them as emitters for TADF OLEDs. dCF3BFCzOXD with the mostly optimized donor/acceptor structures demonstrates the highest efficiency with maximum EQE to 21.4%. Our work provides guidelines on the design of high‐efficiency D‐A type TADF materials.

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Section: Resultsmentioning

confidence: 99%

Fine Tuning of Donor‐Acceptor Structures in Fused‐Carbazole Containing Thermally Activated Delayed Fluorescence Materials towards High‐Efficiency OLEDs

Yuan

Wang

et al. 2023

Chin. J. Chem.

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Impact of Donor and Acceptor Modification on TADF and Roll‐Off Behaviors in Solution Processed OLED

Yang,

Hyeon,

et al. 2024

Advanced Optical Materials

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Up‐conversion of triplet into singlet exciton in the emitting layer is believed to be one of the ways that thermally activated delayed fluorescent (TADF) materials may employ to reduce triplet exciton density hence preventing device quenching by triplet excitons. Yet, two donor‐acceptor type molecules; 5‐(4‐(4,6‐diphenyl‐1,3,5‐triazin‐2‐yl)phenyl)‐12‐(3‐(triphenylsilyl) phenyl)‐5,12‐dihydroindolo[3,2‐a]carbazole (SiPhCzTrz) and 5‐phenyl‐12‐(4‐(4‐phenyl‐6‐(3‐(triphenylsilyl) phenyl)‐1,3,5‐triazin‐2‐yl)pheny‐l)‐5,12‐dihydroindolo [3,2‐a]carbazole (SiTrzPhCz), which exhibited different TADF properties depending on the relative positions of their electron donor unit (PhCz) and electron acceptor unit (Trz), show opposite behaviors. These materials are used as sensitizer in phosphorescent solution‐processed organic light emitting diodes (s‐OLEDs) showing moderately high current efficiencies of 19.3 and 20 cd/A, respectively. SiTrzPhCz exhibits stronger TADF properties compared to SiPhCzTrz; however, these stronger TADF characteristics lead to a more pronounced efficiency roll‐off, mainly due to the longer residence time of excitons in SiTrzPhCz, leading to exciton quenching. In contrast, due to their twisted structures, the efficiency roll‐off is efficiently suppressed, particularly for SiTrzPhCz, when both materials are used as hosts. Their twisted structures promote aggregate‐induced emission and prevent aggregation‐caused quenching. Further analysis of exciton dynamics reveals faster decay rate for both singlet and triplet densities in SiPhCzTrz compared to SiTrzPhCz, indicated by its higher fast prompt emission, kFRET and knrT.

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Acridin-9(10H)-one based thermally activated delayed fluorescence emitter for highly efficient green OLED

Liu

et al. 2023

Dyes and Pigments

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Multichannel charge transfer enhanced radiative decay and RISC in TADF materials containing multiple donors and acceptors

Abstract: Coexistence of through-bond charge transfer (TBCT) and through-space charge transfer (TSCT) is observed to strongly enhance the performance of thermally activated delayed fluorescence (TADF) materials that contain multiple donors and...

Cited by 7 publications

References 39 publications

Fine Tuning of Donor‐Acceptor Structures in Fused‐Carbazole Containing Thermally Activated Delayed Fluorescence Materials towards High‐Efficiency OLEDs

Fine Tuning of Donor‐Acceptor Structures in Fused‐Carbazole Containing Thermally Activated Delayed Fluorescence Materials towards High‐Efficiency OLEDs

Impact of Donor and Acceptor Modification on TADF and Roll‐Off Behaviors in Solution Processed OLED

Acridin-9(10H)-one based thermally activated delayed fluorescence emitter for highly efficient green OLED

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