Suchergebnisse

SK acknowledges the financial support from European Union's Horizon 2020 research and innovation programme under Marie Skłodowska Curie Individual Fellowship (MCIF; Agreement No. 748430‐THF‐OLED). ; Three D‐π‐A type linearly‐extended emitters, based on diphenylamine ( DPA ) as the donor and 2,4,6‐triphenyl‐1,3,5‐triazine ( TRZ ) as the acceptor, were synthesized and their optoelectronic properties characterized. The introduction of an additional phenyl or phenylethynyl π‐spacer results in an enhancement of the molar extinction coefficient and a systematic bathochromic shift of the charge‐transfer transition in the absorption spectra. A mirrored bathochromic shift in the photoluminescence spectra is also observed with increasing conjugation of the bridge moiety. All three compounds show high photoluminescence quantum yields and moderate singlet‐triplet excited state energy gaps, ΔE ST, of 0.26‐0.37 eV were observed in 10 wt% doped films in mCP as the host matrix. ; Publisher PDF ; Peer reviewed

X.-J.W., I.A., J.A., and T.N. would like to acknowledge the European Union for a Marie Curie ITN Grant (Photo4Future, Grant No. 641861). C.S. acknowledges the European Union for a Marie Curie European post-doctoral fellowship (FlowAct, Grant No. 794072). We would like to thank the Engineering and Physical Sciences Research Council for financial support (EP/M02105X/1). C. L. thanks the Prof. & Mrs Purdie Bequests Scholarship and AstraZeneca for his PhD Studentship. ; A continuous‐flow, visible‐light‐promoted method has been developed to overcome the limitations of iron‐catalyzed Kumada–Corriu cross‐coupling reactions. A variety of strongly electron rich aryl chlorides, previously hardly reactive, could be efficiently coupled with aliphatic Grignard reagents at room temperature in high yields and within a few minutes' residence time, considerably enhancing the applicability of this iron‐catalyzed reaction. The robustness of this protocol was demonstrated on a multigram scale, thus providing the potential for future pharmaceutical application. ; Publisher PDF ; Peer reviewed

EZ-C acknowledges the University of St Andrews and EPSRC (EP/M02105X/1) for financial support. DE thanks funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 700961. DJ acknowledges the European Research Council (Marches grant n°278845) and the RFI Lumomat for financial support. ; Synthetic self-assembly is a powerful technique for the bottom-up construction of discrete and well-defined polyhedral nanostructures resembling the spherical shape of large biological systems. In recent years, numerous Archimedean-shaped coordination cages have been reported based on the assembly of bent monodentate organic ligands containing two or more distal pyridyl rings and square planar PdII ions. The formation of photoactive PdII metallamacrocycles and cages, however, remain rare. Here we report the first examples of emissive and homochiral supramolecular cages of the form of [Ir8Pd4]16+. These cages provide a suitably sized cavity to host large guest molecules. Importantly, encapsulation and energy transfer have been observed between the blue-emitting NBu4[Ir(dFppy)2(CN)2] guest and the red-emitting Δ8-[Ir8Pd4]16+ cage. ; Publisher PDF ; Peer reviewed

The work was supported by the European Union's Horizon 2020 research and innovation program under Grant Agreement N°. 646176 (EXTMOS project). A.P. acknowledges the financial support from the Marie Curie Fellowship (MILORD project, N°. 748042). Computational resources have been provided by the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifiques de Belgique (F.R.S.-FNRS) under Grant No. 2.5020.11, as well as the Tier-1 supercomputer of the Fédération Wallonie-Bruxelles, infrastructure funded by the Walloon Region under the grant agreement n1117545. The St Andrews team would like to thank the Leverhulme Trust (RPG-2016-047) and EPSRC (EP/P010482/1) for financial support. ; Unlike conventional thermally activated delayed fluorescence chromophores, boron-centered azatriangulene-like molecules combine a small excited-state singlet-triplet energy gap with high oscillator strengths and minor reorganization energies. Here, using highly correlated quantum-chemical calculations, we report this is driven by short-range reorganization of the electron density taking place upon electronic excitation of these multi-resonant structures. Based on this finding, we design a series of π-extended boron- and nitrogen-doped nanographenes as promising candidates for efficient thermally activated delayed fluorescence emitters with concomitantly decreased singlet-triplet energy gaps, improved oscillator strengths and core rigidity compared to previously reported structures, permitting both emission color purity and tunability across the visible spectrum. ; Publisher PDF ; Peer reviewed

Unlike conventional thermally activated delayed fluorescence chromophores, boron-centered azatriangulene-like molecules combine a small excited-state singlet-triplet energy gap with high oscillator strengths and minor reorganization energies. Here, using highly correlated quantum-chemical calculations, we report this is driven by short-range reorganization of the electron density taking place upon electronic excitation of these multi-resonant structures. Based on this finding, we design a series of π-extended boron- and nitrogen-doped nanographenes as promising candidates for efficient thermally activated delayed fluorescence emitters with concomitantly decreased singlet-triplet energy gaps, improved oscillator strengths and core rigidity compared to previously reported structures, permitting both emission color purity and tunability across the visible spectrum. ; The work was supported by the European Union's Horizon 2020 research and innovation program under Grant Agreement N°. 646176 (EXTMOS project). A.P. acknowledges the financial support from the Marie Curie Fellowship (MILORD project, N°. 748042). Computational resources have been provided by the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifiques de Belgique (F.R.S.-FNRS) under Grant No. 2.5020.11, as well as the Tier-1 supercomputer of the Fédération Wallonie-Bruxelles, infrastructure funded by the Walloon Region under the grant agreement n1117545. The St Andrews team would like to thank the Leverhulme Trust (RPG-2016-047) and EPSRC (EP/P010482/1) for financial support.

This project has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreements No. 838009 (TSFP) and No 812872 (TADFlife). D.S. acknowledges support from the Marie Skłodowska-Curie Individual Fellowship (TSFP), the National Postdoctoral Program for Innovative Talents (BX201700164), and the Jiangsu Planned Projects for Postdoctoral Research Funds (2018K011A). S.B. acknowledges support from the German Science Foundation (392306670/HU2362). The St Andrews team thank the Leverhulme Trust (RPG2016047) and EPSRC (EP/P010482/1) for financial support. X.Z. would like to thank the support from the National Key Research & Development Program of China (Grant No. 2020YFA0714601, 2020YFA0714604), the National Natural Science Foundation of China (Grant No. 52130304, 51821002), Suzhou Key Laboratory of Functional Nano & Soft Materials, Collaborative Innovation Center of Suzhou Nano Science & Technology, the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), the 111 Project, Joint International Research Laboratory of Carbon-Based Functional Materials and Devices. E. Z.-C. is a Royal Society Leverhulme Trust Senior Research fellow (SRF\R1\201089). ; The development of high-performance solution-processed organic light-emitting diodes (OLEDs) remains a challenge. An effective solution, highlighted in this work, is to use highly efficient thermally activated delayed fluorescence (TADF) dendrimers as emitters. Here, the design, synthesis, density functional theory (DFT) modeling, and photophysics of three triazine-based dendrimers, tBuCz2pTRZ , tBuCz2mTRZ , and tBuCz2m2pTRZ , is reported, which resolve the conflicting requirements of achieving simultaneously a small ΔEST and a large oscillator strength by incorporating both meta- and para-connected donor dendrons about a central triazine acceptor. The solution-processed OLED containing a host-free emitting layer exhibits an excellent maximum external quantum ...

This project is supported by the Helmholtz Association Program at the Karlsruhe Institute of Technology. The German Research Foundation (formally Deutsche Forschungsgemeinschaft DFG) in the framework of SFB1176 Cooperative Research Centre "Molecular Structuring of Soft Matter" (CRC1176, A4, B3, C2, C6) and the cluster 3D Matter Made To Order funded under Germany's Excellence Strategy (3DMM2O EXC-2082/1-390761711) are greatly acknowledged for financial contributions. ZZ acknowledges the financial support from Chinese Scholarship Council (CSC) for his PhD studies. SK acknowledges the financial support from European Union's Horizon 2020 research and innovation programme under Marie Skłodowska Curie Individual Fellowship (MCIF; Agreement No. 748430-THF-OLED). S.B. acknowledges support from the Bayrisches Staatsministerium für Wissenschaft und Kunst (Stmwk) in the framework of the initiative "SolTech" as well as from the German Science foundation (DFG) (no. 392306670). ; Six luminophores bearing an OBO-fused benzo[fg]tetracene core as an electron-acceptor were designed and synthesized. The molecular structures of three molecules ( PXZ-OBO, 5PXZ OBO, 5DMAC-OBO ) were determined by single crystal X-ray diffraction studies and revealed significant torsion between the donor moieties and the OBO acceptor with dihedral angles between 75.5° and 86.2°. Photophysical studies demonstrate that blue and deep blue emission can be realized with photoluminescence maxima (λPL) ranging from 415 nm to 480 nm in mCP films. The emission energy is modulated by simply varying the strength of the donor heterocycle, the number of donors and their position relative to the acceptor. Although the DMAC-derivatives show negligible delayed emission due to their large singlet-triplet excited state energy difference, ΔEST, PXZ-based molecules, especially PXZ-OBO with an experimental ΔEST of 0.25 eV, demonstrate delayed emission in blend mCP films at room temperature, which suggests triplet exciton harvesting occurs in these samples, potentially by thermally activated delayed fluorescence (TADF). ; Publisher PDF ; Peer reviewed

This work has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 838009 (TSFP) and No 812872 (TADFlife). D.S. acknowledges support from the Marie Skłodowska-Curie Individual Fellowship, the National Postdoctoral Program for Innovative Talents (BX201700164), the Jiangsu Planned Projects for Postdoctoral Research Funds (2018K011A). E.Z.-C. is a Royal Society Leverhulme Trust Senior Research fellow (SRF∖R1∖201089). The St Andrews team would also like to thank the Leverhulme Trust (RPG-2016047) and EPSRC (EP/P010482/1) for financial support. This work was also supported by Comunidad de Madrid (Spain) – multiannual agreement with UC3M ("Excelencia para el Profesorado Universitario" – EPUC3M14) – Fifth regional research plan 2016-2020 and by the Spanish Ministry of Science, Innovation and Universities (MICINN) through project RTI2018-101020-B-100. X.Z. would like to thank the support from the National Key Research & Development Program of China (Grant No. 2020YFA0714601, 2020YFA0714604), the National Natural Science Foundation of China (Grant No. 52130304, 51821002), Suzhou Key Laboratory of Functional Nano & Soft Materials, Collaborative Innovation Center of Suzhou Nano Science & Technology, the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), the 111 Project, Joint International Research Laboratory of Carbon-Based Functional Materials and Devices. ; The potential of dendrimers exhibiting thermally activated delayed fluorescence (TADF) as emitters in solution-processed organic light-emitting diodes (OLEDs) has to date not yet been realized. This in part is due to a poor understanding of the structure–property relationship in dendrimers where reports of detailed photophysical characterization and mechanism studies are lacking. In this report, using absorption and solvatochromic photoluminescence studies in solution, the origin and character of the lowest excited electronic ...

Funding: We thank EU horizon 2020 Grant Agreement No. 812872 (TADFlife) for funding. SK acknowledges the financial support from European Union's Horizon 2020 research and innovation programme under Marie Skłodowska Curie Individual Fellowship (MCIF; Agreement No. 748430- THF-OLED). ; Commonly, thermally activated delayed fluorescence (TADF) emitters present a twisted donor–acceptor structure. Here, electronic communication is mediated through-bond via π-conjugation between donor and acceptor groups. A second class of TADF emitters are those where electronic communication between donor and acceptor moieties is mediated through-space. In these through-space charge-transfer (TSCT) architectures, the donor and acceptor groups are disposed in a pseudocofacial orientation and linked via a bridging group that is typically an arene (or heteroarene). In most of these systems, there is no direct evidence that the TSCT is the dominant contributor to the communication between the donor and acceptor. Herein we investigate the interplay between through-bond localized excited (LE) and charge-transfer (CT) states and the TSCT in a rationally designed emitter, TPA-ace-TRZ , and a family of model compounds. From our photophysical studies, TSCT TADF in TPA-ace-TRZ is unambiguously confirmed and supported by theoretical modeling. ; Publisher PDF ; Peer reviewed

The authors thank the German Research Foundation (DFG) for financial support through SFB 1176 (Project A4) and Helmholtz Energy Materials Foundry HEMF funding of the Helmholtz Association. M.J. acknowledges support from the Karlsruhe School of Optics & Photonics (KSOP) graduate school. SMS thanks the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no 838885 (NarrowbandSSL). The St Andrews team thanks the EPSRC for financial support (EP/P010482/1). ; Understanding triplet exciton diffusion between organic thermally activated delayed fluorescence (TADF) molecules is a challenge due to the unique cycling between singlet and triplet states in these molecules. Although prompt emission quenching allows the singlet exciton diffusion properties to be determined, analogous analysis of the delayed emission quenching does not yield accurate estimations of the triplet diffusion length (because the diffusion of singlet excitons regenerated after reverse-intersystem crossing needs to be accounted for). Herein, we demonstrate how singlet and triplet diffusion lengths can be accurately determined from accessible experimental data, namely the integral prompt and delayed fluorescence. In the benchmark materials 4CzIPN and 4TCzBN, we show that the singlet diffusion lengths are (9.1 ± 0.2) and (12.8 ± 0.3) nm, whereas the triplet diffusion lengths are negligible, and certainly less than 1.0 and 1.2 nm, respectively. Theory confirms that the lack of overlap between the shielded lowest unoccupied molecular orbitals (LUMOs) hinders triplet motion between TADF chromophores in such molecular architectures. Although this cause for the suppression of triplet motion does not occur in molecular architectures that rely on electron resonance effects (e.g. DiKTa), we find that triplet diffusion is still negligible when such molecules are dispersed in a matrix material at a concentration sufficiently low to suppress aggregation. The novel and accurate method of understanding triplet diffusion in TADF molecules will allow accurate physical modeling of OLED emitter layers (especially those based on TADF donors and fluorescent acceptors). ; Publisher PDF ; Peer reviewed

This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska Curie grant agreement No. 838009 (TSFP) and No. 838885 (NarrowbandSSL). D.S. acknowledges support from the Marie Skłodowska-Curie Individual Fellowship, the National Postdoctoral Program for Innovative Talents (BX201700164), the Jiangsu Planned Projects for Postdoctoral Research Funds (2018K011A). The St Andrews team would also like to thank the Leverhulme Trust (RPG-2016047) and EPSRC (EP/P010482/1) for financial support. We thank Umicore AG for the gift of materials. Computational resources have beenprovided by the Consortium des Équipements de Calcul In-tensif (CÉCI), funded by the Fonds de la Recherche Scientifiques de Belgique (F.R.S.-FNRS) under Grant No. 2.5020.11. ; The development of muliple resonance thermally activated delayed fluorescence (MR-TADF) materials possessing narrow emission spectra has attracted significant attention as emitters for high colour purity organic light emitting diodes (OLEDs). In this work, a simple design strategy is introduced to construct a MR-TADF emitter, DDiKTa, through dimerization of the known MR-TADF emitter DiKTa. This design permits concentration quenching to be largely suppressed, which is a known weakness of previously reported MR-TADF emitters. OLEDs based on DDiKTa show an EQEmax of 19% at a doping concentration of 9 wt%. The electrolumicence spectrum is red-shifted into the green, producing a rare example of a green-emitting MR-TADF OLED. ; Publisher PDF ; Peer reviewed

This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska Curie grant agreement No 838885 (NarrowbandSSL) and under the Marie Skłodowska Curie grant agreement No 812872 (TADFlife). S.M.S. acknowledges support from the Marie Skłodowska-Curie Individual Fellowship (grant agreement No 838885 NarrowbandSSL). The St. Andrews team would like to thank the Leverhulme Trust (RPG-2016-047) for financial support. E. Z.-C. is a Royal Society Leverhulme Trust Senior Research fellow (SRF\R1\201089). Computational resources have been provided by the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifiques de Belgique (F. R. S.-FNRS) under Grant No. 2.5020.11, as well as the Tier-1 supercomputer of the Fédération Wallonie-Bruxelles, infrastructure funded by the Walloon Region under the grant agreement n 1117545. ; Developing high-efficiency purely organic blue organic light-emitting diodes (OLEDs) that meet the stringent industry standards is a major current research challenge. Hyperfluorescent device approaches achieve in large measure the desired high performance by combining the advantages of a high-efficiency thermally activated delayed fluorescence (TADF) assistant dopant with a narrowband deep-blue multi-resonant TADF (MR-TADF) terminal emitter. However, this approach requires suitable spectral overlap to support Förster resonance energy transfer (FRET) between the two. Here, a color tuning of a recently reported MR-TADF B,N-heptacene core through control of the boron substituents is demonstrated. While there is little impact on the intrinsic TADF properties—as both singlet and triplet energies decrease in tandem—this approach improves the emission color coordinate as well as the spectral overlap for blue hyperfluorescence OLEDs (HF OLEDs). Crucially, the red-shifted and more intense absorption allows the new MR-TADF emitter to pair with a high-performance TADF assistant dopant and achieve maximum ...

S.W. thanks the China Scholarship Council (201906250199). EZ-C and IDWS acknowledge support from EPSRC (EP/L017008, EP/P010482/1). We are also grateful for financial support from the University of St Andrews Restarting Research Funding Scheme (SARRF) which is funded through the Scottish Funding Council grant reference SFC/AN/08/020. EZ-C is a Royal Society Leverhulme Trust Senior Research fellow (SRF\R1\201089). We would also like to thank the Leverhulme Trust (RPG-2016-047) for financial support. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska Curie grant agreement No 838885 (NarrowbandSSL). S.M.S. acknowledges support from the Marie Skłodowska-Curie Individual Fellowship. Computational resources have been provided by the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifiques de Belgique (F.R.S.-FNRS) under Grant No. 2.5020.11, as well as the Tier-1 supercomputer of the Fédération Wallonie-Bruxelles, infrastructure funded by the Walloon Region under the grant agreement n1117545. Y.O. acknowledges funding by the Fonds de la Recherche Scientifique-FNRS under Grant n° F.4534.21 (MIS-IMAGINE). D.B. is a FNRS Research Director. ; Strategies to tune the emission of multiresonant thermally activated delayed fluorescence (MR-TADF) emitters remain rare. Here, we explore the effect of donor substitution about a MR-TADF core on the emission energy and the nature of the excited state. We decorate different numbers and types of electron-donors about a central MR-TADF core, DiKTa. Depending on the identity and number of donor groups, the excited state either remains short-range charge transfer (SRCT) and thus characteristic of an MR-TADF emitter or becomes a long-range charge transfer (LRCT) that is typically observed in donor–acceptor TADF emitters. The impact is that in three examples that emit from a SRCT state, Cz-DiKTa, Cz-Ph-DiKTa, and 3Cz-DiKTa, the emission remains narrow, while in ...

The St Andrews team would like to thank the Leverhulme Trust (RPG-2016-047) for financial support. Computational resources have been provided by the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifiques de Belgique (F. R. S.-FNRS) under Grant No. 2.5020.11, as well as the Tier-1 supercomputer of the Fédération Wallonie-Bruxelles, infrastructure funded by the Walloon Region under the grant agreement n1117545. We acknowledge support from the European Union's Horizon 2020 research and innovation programme under the ITN TADFlife (GA 812872). Y.O. acknowledges funding by the Fonds de la Recherche Scientifique-FNRS under Grant no. F.4534.21 (MIS-IMAGINE). D. B. is a FNRS Research Director. EZ-C is a Royal Society Leverhulme Trust Senior Research fellow (SRF\R1\201089). ; In this work we present a new multi-resonance thermally activated delayed fluorescence (MR-TADF) emitter paradigm, demonstrating that the structure need not require the presence of acceptor atoms. Based on an in silico design, the compound DiICzMes4 possesses a red-shifted emission, enhanced photoluminescence quantum yield, and smaller singlet-triplet energy gap, ΔEST, than the parent indolocarbazole that induces MR-TADF properties. Coupled cluster calculations accurately predict the magnitude of the ΔEST when the optimized singlet and triplet geometries are used. Slow yet optically detectable reverse intersystem crossing contributes to low efficiency in organic light-emitting diodes using DiICzMes4 as the emitter. However, when used as a terminal emitter in combination with a TADF assistant dopant within a hyperfluorescence device architecture, maximum external quantum efficiencies of up to 16.5% were achieved at CIE (0.15, 0.11). This represents one of the bluest hyperfluorescent devices reported to date. Simultaneously, recognising that MR-TADF emitters do not require acceptor atoms reveals an unexplored frontier in materials design, where yet greater performance may yet be discovered. ; Publisher PDF ; Peer reviewed

SK acknowledges the financial support from European Union's Horizon 2020 research and innovation programme under Marie Skłodowska Curie Individual Fellowship (MCIF; Agreement No. 748430-THF-OLED). P. R acknowledges support from a Marie Skłodowska-Curie Individual Fellowship (No. 749557). The work has been supported in Mons by European Union through the Interreg V initiative France-Wallonie-Vlaanderen project LUMINOPTEX and the Belgian National Fund for Scientific Research (FRS-FNRS). Computational resources were provided by the Consortium des Équipements de Calcul Intensif (CÉCI) funded by F. R. S.-FNRS under Grant 2.5020.11. J. C. is an FNRS research director. Y. O. acknowledges funding by the Fonds de la Recherche Scientifique-FNRS under Grant no F.4534.21 (MIS-IMAGINE). We acknowledge the research support from Natural Sciences and Engineering Research Council Canada (NSERC, DG RGPIN-2013-201697, DG RGPIN-2018-06556, and SPG STPGP-2016-493924), Canada Foundation of Innovation, Ontario Innovation Trust (CFI/OIT, 9040) and Western University. J. R. A. appreciates the Ontario graduate scholarships (2018–2022). EZ-C is a Royal Society Leverhulme Trust Senior Research fellow (SRF\R1\201089). ; Aiming to develop efficient blue-emitting thermally activated delayed fluorescence (TADF) compounds, we have designed and synthesized derivatives of the well-known sky-blue emitter 2CzPN that contain electron-accepting phosphine chalcogenide groups to stabilize the HOMO level relative to the pristine compound, thus increasing the HOMO–LUMO gap and blue-shifting the emission wavelength. By cyclic voltammetry, photophysical data and quantum-chemical calculations, it was found that polar solvents and matrices validated the proposed concept, but these trends were not recovered in non-polar media. The suitability of these 2CzPN derivatives in polar matrices for optoelectronic applications was explored with electrochemiluminescence (ECL) by measuring emission delays, radical stability, emission stabilities, emission efficiencies ...