Modulating the triplet chromophore environment to prolong the emission lifetime of ultralong organic phosphorescence

Yang, Ge; Lv, Anqi; Xu, Zixuan; Song, Zhicheng; Shen, Kang; Lin, Cheng-Kuan; Niu, Guowei; Ma, Huili; Shi, Huifang; An, Zhongfu

doi:10.1039/d2tc00836j

Cited by 9 publications

(6 citation statements)

References 41 publications

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“…There is a rise in the C 2 C 6 triplet from 1 to 10 μs, reaching a plateau at ∼20 μs, then finally decaying monoexponentially with a notably long lifetime of 450 μs. This is 2 orders of magnitude longer than the triplet lifetime of C 16 and 2–3 orders of magnitude longer than the triplets of well-known polymers with a similar bandgap such as PCDTBT, APFO3, and IF8TBTT, and over 4 times longer than the low-triplet-energy small-molecule rubrene. , Table S1 compares the triplet lifetime obtained in this work with small molecules and polymers with different bandgaps seen in the literature. ,,,− The rise in triplet population on the μs timescale for C 2 C 6 indicates that these triplets are not formed from standard intersystem crossing. Instead, they are formed upon a bimolecular charge recombination process, as can be observed by the C 2 C 6 bimolecular polaron decay kinetics matching the rise of the triplets (Figure S4).…”

Section: Resultsmentioning

confidence: 60%

“…In this study, we report two polymers based on the BDT-T monomer with triplet states with a nearly millisecond lifetime, which are some of the longest triplet lifetimes reported to date for red-emitting conjugated polymer films, closing the gap with blue absorbing molecular crystals. [32][33][34]38,43 This is achieved using two different triplet generation mechanisms. The first is by generating triplets via slow bimolecular electron−hole recombination, and the second by incorporating a Pd porphyrin into the polymer backbone to act as a triplet sensitizer, whereby polymer triplets are formed by back energy transfer from the porphyrin.…”

Section: ■ Conclusionmentioning

confidence: 99%

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Generating Long-Lived Triplet Excited States in Narrow Bandgap Conjugated Polymers

et al. 2023

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Narrow bandgap conjugated polymers are a heavily studied class of organic semiconductors, but their excited states usually have a very short lifetime, limiting their scope for applications. One approach to overcome the short lifetime is to populate long-lived triplet states for which relaxation to the ground state is forbidden. However, the triplet lifetime of narrow bandgap polymer films is typically limited to a few microseconds. Here, we investigated the effect of film morphology on triplet dynamics in redemitting conjugated polymers based on the classic benzodithiophene monomer unit with the solubilizing alkyl side chains C 16 and C 2 C 6 and then used Pd porphyrin sensitization as a further strategy to change the triplet dynamics. Using transient absorption spectroscopy, we demonstrated a 0.45 ms triplet lifetime for the more crystalline nonsensitized polymer C 2 C 6 , 2−3 orders of magnitude longer than typically reported, while the amorphous C 16 had only a 5 μs lifetime. The increase is partly due to delaying bimolecular electron−hole recombination in the more crystalline C 2 C 6, where a higher energy barrier for charge recombination is expected. A triplet lifetime of 0.4 ms was also achieved by covalently incorporating 5% of Pd porphyrin into the C 16 polymer, which introduced extra energy transfer steps between the polymer and porphyrin that delayed triplet dynamics and increased the polymer triplet yield by 7.9 times. This work demonstrates two synthetic approaches to generate the longest-lived triplet excited states in narrow bandgap conjugated polymers, which is of necessity in a wide range of fields that range from organic electronics to sensors and bioapplications.

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Section: Resultsmentioning

confidence: 60%

Section: ■ Conclusionmentioning

confidence: 99%

Generating Long-Lived Triplet Excited States in Narrow Bandgap Conjugated Polymers

et al. 2023

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“…40 We found that the surrounding of the triplet chromophore is critical to regulating the organic phosphorescence lifetime. For example, from a series of phenoxazine-substituted triazine derivatives (29−32) 41 and Cl-substituted carbazole-based isomers (33−35), 42 the intermolecular interactions between chromophores of phenoxazines or carbazoles are gradually weakened by adjusting the manipulation of alky chains and positions of the phenyl ring, resulting in the increase of UOP lifetimes (Figure 3a). Impressively, there is no UOP observed when the electronic coupling between triplet chromophores is weak.…”

Section: Tuning the Emission Lifetimesmentioning

confidence: 99%

Section: Property Manipulation Of Uop Materialsmentioning

confidence: 99%

Ultralong Organic Phosphorescence: From Material Design to Applications

et al. 2022

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Conspectus Organic phosphorescence is defined as a radiative transition between the different spin multiplicities of an organic molecule after excitation; here, we refer to the photoexcitation. Unlike fluorescence, it shows a long emission lifetime (∼μs), large Stokes shift, and rich excited state properties, attracting considerable attention in organic electronics during the past years. Ultralong organic phosphorescence (UOP), a type of persistent luminescence in organic phosphors, shows an emission lifetime of over 100 ms normally according to the resolution limit of the naked eye. According to the Jablonski energy diagram, two prerequisites are necessary for UOP generation and enhancement. One is to promote intersystem crossing (ISC) of the excitons from the excited singlet to triplet states by enhancing the spin–orbit coupling (SOC); the other is to suppress the nonradiative transitions of the excitons from the excited triplet states. In this Account, we will give a summary of our research on ultralong organic phosphorescence, including the design of materials, manipulation of properties, fabrication of nano/microstructures, and function applications. First, we give a brief introduction to the UOP development. Then, we discuss the constructed methods of UOP materials from the inter/intramolecular interaction types, including π–π interactions, intermolecular hydrogen bonds, halogen bonds, ionic bonds, covalent bonds, and so on. These effective interactions can build a rigid environment to restrain the nonradiative transitions from the molecular motions or external quenching by oxygen, moisture, or heat, and thus enhance the UOP performance. Next, the manipulation of UOP properties, containing excitation wavelength, emission colors, lifetimes, and quantum efficiency (QE), through molecular or crystal engineering will be summarized. Recently, the excitation wavelengths of the materials for UOP can be regulated in different regions, such as UV, visible light, and X-ray; the emission colors of UOP can cover the whole visible-light region, from deep blue to red; the phosphorescence lifetime of UOP materials can reach 2.5 s, and the quantum efficiency can be achieved up to 96.5%. Moreover, we will present the fabrication of micro/nanoscale UOP materials, including the preparation of micro/nanostructure, optical performance, and device fabrication. Afterward, we will review the potential applications of UOP materials in organic/bio-optoelectronics, such as information encryption, bioimaging, sensing, afterglow display, etc. Finally, an outlook on the development of UOP materials and applications will be proposed.

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“…Several strategies have been explored to induce efficient phosphorescence from purely organic molecules, such as leveraging n → π* transitions and the heavy-atom effect, which can promote a strong spin–orbit coupling (SOC) process. 4 For instance, Jin et al reported the use of 1,3,5-trifluoro-2,4,6-triiodobenzene (TITFB) as a simple RTP material, demonstrating its potential in promoting n → π* transitions. 5 However, TITFB exhibited weak phosphorescence, limiting its applicability in OLED devices.…”

Section: Introductionmentioning

confidence: 99%

Achieving pure room temperature phosphorescence (RTP) in phenoselenazine-based organic emitters through synergism among heavy atom effect, enhanced n → π* transitions and magnified electron coupling by the A–D–A molecular configuration

Zhong,

Liu,

Yue

et al. 2024

Chem. Sci.

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Modulating the triplet chromophore environment to prolong the emission lifetime of ultralong organic phosphorescence

Abstract: Molecular environment plays a vital role in regulating the photophysical properties of the optoelectronic functional materials. Here, in a series of phenoxazine derivatives with a triazine core and double-branched structures,...

Cited by 9 publications

References 41 publications

Generating Long-Lived Triplet Excited States in Narrow Bandgap Conjugated Polymers

Generating Long-Lived Triplet Excited States in Narrow Bandgap Conjugated Polymers

Ultralong Organic Phosphorescence: From Material Design to Applications

Achieving pure room temperature phosphorescence (RTP) in phenoselenazine-based organic emitters through synergism among heavy atom effect, enhanced n → π* transitions and magnified electron coupling by the A–D–A molecular configuration

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