Pyridine-functionalized carbazole donor and benzophenone acceptor design for thermally activated delayed fluorescence emitters in blue organic light emitting diodes

The authors thank the Marie Skłodowska-Curie Individual Fellowship (MCIF, no 749557), the Leverhulme Trust (RPG-2016-047) and EPSRC (EP/P010482/1) for financial support.In this paper we report a new molecular design approach for blue emitting thermally activated delayed fluorescence (TADF) molecules. The two novel TADF emitters, (4-(3,6-di(pyridin-3-yl)-9H-carbazol-9- yl)phenyl)(phenyl)methanone ( 3PyCzBP ), and (4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl)(phenyl)methanone ( 4PyCzBP ) possess a pyridine-functionalized carbazole donor and a benzophenone acceptor. Both compounds shows broad charge-transfer emission in DCM with a λmax at 497 nm and a photoluminescence quantum yield, ΦPL of 56% for 3PyCzBP and a λmax at 477 nm and a ΦPL of 52% for 4PyCzBP . The ΦPL decreased to 18% and 10%, respectively for 3PyCzBP and 4PyCzBP in the presence of O2 confirming that triplet states involved in emission. The PMMA doped (10 wt%) films show blue-shifted emission with λmax at 450 and 449 nm for 3PyCzBP and 4PyCzBP , respectively. The maximum ΦPL of 23.4% is achieved for these compounds in PMMA doped film. Difference in energy between the singlet and triplet excited states (ΔEST) is very small at 0.06 eV and 0.07 eV for 3PyCzBP and 4PyCzBP , respectively. Multilayer organic light emitting diode devices fabricated using these molecules as emitters show that the maximum efficiency (EQEmax) of the blue devices is 5.0%.PostprintPeer reviewe

Highly fluorescent emitters based on triphenylamine‐π‐triazine (D‐π‐A) system : effect of extended conjugation on singlet‐triplet energy gap

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 PDFPeer reviewe

High performance non-doped green organic light emitting diode via delayed fluorescence

P. G. thanks the Science & Engineering Research Board (SERB), India, for the Start-up Research Grant (SRG) (Grant No: SRG/2020/000161). E.Z-C. thanks the Engineering and Physical Sciences Research Council (EPSRC) EP/P010482/1 for support. P. R. thanks the Indian Institute of Science (IISc) for generous financial support and the Science & Engineering Research Board (SERB), India, for the SERB-Power Grant (SPG) (Grant No: SPG/2020/000107). B.S. thank IISc for the C. V. Raman Fellowship under the Institute of Eminence (IoE).Non-doped, delayed fluorescence organic light-emitting diodes (OLEDs) provide a route to high performance devices and simplified device fabrication. Here, two ambipolar anthracene derivatives containing a hole-transporting di-p-tolylamine and a carbazole and an electron-transporting phosphine oxide moiety are rationally designed and synthesized. The thermal and optoelectronic properties were investigated and the neat films of these compounds show high photoluminescence quantum yields of 84–87%. Non-doped OLEDs with these luminogens exhibit green emission at ∼545 nm and an EQEmax of over 7.2% due to the delayed fluorescence resulting from triplet–triplet annihilation (TTA). The devices show a high luminance of over 104 400 cd m−2. Power efficiency and current efficiency maxima are up to 23.0 lm W−1 and 28.3 cd A−1, respectively. Moreover, the devices show very low efficiency roll-off and retain 90% of the maximum efficiency even at 20 000 cd m−2. When combined with a thermally activated delayed fluorescent (TADF) assistant dopant, the green-emitting OLEDs show a high EQEmax of 17.8%.PostprintPeer reviewe

Molecular design strategy for a two-component gel based on a thermally activated delayed fluorescence emitter

The authors thank the Marie Skłodowska-Curie Individual Fellowship (MCIF, no 749557), the Leverhulme Trust (RPG-2016-047) and EPSRC (EP/P010482/1) for financial support. We thank the EPSRC UK National Mass Spectrometry Facility at Swansea University for analytical services.Luminescent materials that can spontaneously assemble into highly ordered networks are essential to improve the quality of thin films in stacked device architectures and enhance the performances of solution processed OLEDs. Herein, we report two pyridine-decorated thermally activated delayed fluorescence (TADF) emitters, 3PyCzBP and 4PyCzBP . 4PyCzBP shows robust two component gel formation in the presence of either tartaric acid or succinic acid along with significant emission enhancement. Morphology studies reveal that these gels consist of homogeneous nanofibers assembled in hierarchical supramolecular networks. Transient photoluminescence spectra confirm that the gels emit via a TADF mechanism, making them the first examples of TADF gels. These nanofibers are promising candidates as self-assembled emitting nanofibers in thin films in solution-processed OLEDs.PostprintPeer reviewe

Solvent-Tuned Supramolecular Assembly of Fluorescent Catechol/Pyrene Amphiphilic Molecules

The synthesis and structuration of a novel low‐molecular‐weight amphiphilic catechol compound is reported. The combination of a hydrophilic tail containing a catechol unit and a pyrene‐based hydrophobic head favors solvent‐tuned supramolecular assembly. Formation of hollow nanocapsules/vesicles occurs in concentrated solutions of polar protic and nonprotic organic solvents, whereas a fibril‐like aggregation process is favored in water, even at low concentrations. The emission properties of the pyrene moiety allow monitoring of the self‐assembly process, which could be confirmed by optical and electronic microscopy. In organic solvents and at low concentrations, this compound remains in its nonassembled monomeric form. As the concentration increases, the aggregation containing preassociated pyrene moieties becomes more evident up to a critical micellar concentration, at which vesicle‐like structures are formed. In contrast, nanosized twist beltlike fibers are observed in water, even at low concentrations, whereas microplate structures appear at high concentrations. The interactions between molecules in different solvents were studied by using molecular dynamics simulations, which have confirmed different solvent‐driven supramolecular interactions.Fil: Nador, Fabiana Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina. Consejo Superior de Investigaciones Científicas; EspañaFil: Wnuk, Karolina. Consejo Superior de Investigaciones Científicas; EspañaFil: Roscini, Claudio. Consejo Superior de Investigaciones Científicas; EspañaFil: Solorzano, Ruben. Consejo Superior de Investigaciones Científicas; España. Universitat Autònoma de Barcelona; EspañaFil: Faraudo, Jordi. Consejo Superior de Investigaciones Científicas; EspañaFil: Ruiz Molina, Daniel. Consejo Superior de Investigaciones Científicas; EspañaFil: Novio, Fernando. Universitat Autònoma de Barcelona; España. Consejo Superior de Investigaciones Científicas; Españ

Substitution effects on a new pyridylbenzimidazole acceptor for thermally activated delayed fluorescence and their use in organic light-emitting diodes

The St Andrews team would like to thank the Leverhulme Trust (RPG-2016-047) for financial support. P.R. acknowledges support from a Marie Skłodowska-Curie Individual Fellowship (MCIF; No. 749557). S.M.S acknowledges support from the Marie Skłodowska-Curie Individual Fellowship, grant 27 agreement no. 838885 (NarrowbandSSL). 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 n° F.4534.21 (MIS-IMAGINE). D.B. is a FNRS Research Director.In this work a new acceptor is used for use in thermally activated delayed fluorescence (TADF) emitters, pyridylbenzimidazole, which when coupled with phenoxazine allows efficient TADF to occur. N-functionalization of the benzimidazole using methyl, phenyl, and tert-butyl groups permits color tuning and suppression of aggregation-caused quenching (ACQ) with minimal impact on the TADF efficiency. The functionalized derivatives support a higher doping of 7 wt% before a fall-off in photoluminescence quantum yields is observed, in contrast with the parent compound, which undergoes ACQ at doping concentrations greater than 1 wt%. Complex conformational dynamics, reflected in the time-resolved decay profile, is found. The singlet−triplet energy gap, ΔEST, is modulated by N-substituents of the benzimidazole and ranges of between 0.22 and 0.32 eV in doped films. Vacuum-deposited organic light-emitting diodes, prepared using three of the four analogs, show maximum external quantum efficiencies, EQEmax, of 23.9%, 22.2%, and 18.6% for BIm(Me)PyPXZ , BIm(Ph)PyPXZ , and BImPyPXZ , respectively, with a correlated and modest efficiency roll-off at 100 cd m–2 of 19% 13%, and 24% of the EQEmax, respectively.Publisher PDFPeer reviewe

Photoluminescence and electrochemiluminescence of thermally activated delayed fluorescence (TADF) emitters containing diphenylphosphine chalcogenide-substituted carbazole donors

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 and emission spectra. Some of the 2CzPN derivatives showed an unprecedented delayed onset of the ECL, and delayed rising time to the ECL maximum, as well as long ECL emission decay. All of these mentioned delay times suggest that these luminophores primarily emit via organic long-persistent electrochemiluminescence (OLECL) mechanisms. The derivatization of the donor groups of the emitters affected both the radical stability and the predominant emission mechanism, providing important insight into their potential as emitters in solid-state electroluminescent devices.Publisher PDFPeer reviewe

Using the Mechanical Bond to Tune the Performance of a Thermally Activated Delayed Fluorescence Emitter**

We report the characterization of rotaxanes based on a carbazole-benzophenone thermally activated delayed fluorescence luminophore. We find that the mechanical bond leads to an improvement in key photophysical properties of the emitter, notably an increase in photoluminescence quantum yield and a decrease in the energy difference between singlet and triplet states, as well as fine tuning of the emission wavelength, a feat that is difficult to achieve when using covalently bound substituents. Computational simulations, supported by X-ray crystallography, suggest that this tuning of properties occurs due to weak interactions between the axle and the macrocycle that are enforced by the mechanical bond. This work highlights the benefits of using the mechanical bond to refine existing luminophores, providing a new avenue for emitter optimization that can ultimately increase the performance of these molecules

Routine based intervention in the context of group sessions with families

Suvremeni pristupi u ranoj intervenciji naglašavaju važnost podrške roditeljima i njihovu snažnu uključenost u sve oblike intervencija. Naglasak je na poštivanju razvojnih načela, koja su jednaka za svu djecu (s razvojnim poteškoćama ili bez njih). Razvojne miljokaze djeca dostižu interakcijom s odraslima te aktivnostima (rutinama), koje su dio njihove prirodne sredine. S obzirom na specifičnosti djece s razvojnim odstupanjima, roditeljima je puno izazovnije uključiti djecu u svakodnevne rutine, iskoristiti ih i razumjeti kao trenutke učenja i poticanja. S ciljem pružanja podrške roditeljima u organiziranju svakodnevnih rutina, radi poticanja sociokomunikacijskog razvoja, organizirane su radionice na kojima se roditelje poučavalo strategijama – kako iskoristiti svakodnevne aktivnosti, rutine u poticanju djetetova razvoja. Organizirano je 5 grupa roditelja (35 roditelja) djece sa sumnjom ili već utvrđenim poremećajem iz spektra autizma (21 dijete). Svaka grupa imala je 12 strukturiranih susreta, nakon kojih su roditelji ispunili evaluacijski upitnik i ocijenili zadovoljstvo programom. U slobodnom dijelu upitnika roditelji su iznimno visoko ocijenili dobivene materijale, kao i razmjenu iskustava s drugim roditeljima. Rezultati pokazuju da intervencijski pristup koji podržava roditelje da ugrađuju razvojne ciljeve u svakodnevne rutine, iako kod nas neuobičajen i nov, roditelji vrlo pozitivno ocjenjuju te su njime zadovoljni. Zaključujemo da su roditelji time dobili vrlo uspješan i snažan alat, koji im pomaže da potiču dijete u raznim vještinama. Također, poučavanje roditelja novim vještinama u grupi s njihovom djecom, pokazalo se poželjnim oblikom rada i preporučuje se češće primjenjivati taj oblik rada u svakodnevnoj praksi.Contemporary approaches to early intervention emphasize the importance of supporting parents and their strong involvement in all forms of intervention. Emphasis has been put on respecting developmental principles that are the same for all children (with or without development difficulties). Children reach developing milestones through interaction with adults and activities (routines) that are part of their natural environment. Because of the specificities of children with developmental disabilities, it is much more demanding for parents to include them in everyday routines, use them and understand them as moments of learning and encouragement. With the aim of providing support to parents in organizing daily routines for promoting socio-communication development, group sessions were organized in which parents were taught strategies for utilizing everyday activities and routines in encouraging child’s development. Five groups of parents (35 parents) of children with suspected or already diagnosed autism spectrum disorders (21 children) have been formed. Each group had 12 structured meetings, after which parents completed the evaluation questionnaire and evaluated the satisfaction with the program they were involved in together with their children. The evaluation questionnaire was highly appreciated by parents, especially regarding communication with experts, content and applicability of the program. In the open-ended part of the questionnaire, parents highly rated the obtained material, as well as the exchange of experiences with other parents. The findings suggest that an intervention approach that supports parents in incorporating developmental goals into everyday routines is a very successful and powerful tool that helps parents encourage a child in various skills. Also, teaching parents new skills together with their children proved to be a very good form of work and it is highly recommended to apply this form more frequently in everyday practice

Improving processability and efficiency of Resonant TADF emitters : a design strategy

This work is funded by the EC through the Horizon 2020 Marie Sklodowska-Curie ITN project TADFlife. The St Andrews team would also like to thank the Leverhulme Trust (RPG-2016- 047) and EPSRC (EP/P010482/1) 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. AP acknowledges the financial support from the Marie Curie Fellowship (MILORD project, N°. 748042). DB is a FNRS Research Director. We thank Franck-Julian Kahle for support with data analysis.A new design strategy is introduced to address a persistent weakness with resonance thermally activated delayed fluorescence (R-TADF) emitters to reduce aggregation-caused quenching effects, which we identify as one of the key limiting factors. The emitter Mes3DiKTa shows an improved photoluminescence quantum yield of 80% compared to 75% for the reference DiKTa in 3.5 wt% mCP. Importantly, emission from aggregates, even at high doping concentrations, is eliminated and aggregation-caused quenching is strongly curtailed. For both molecules, triplets are almost quantitatively upconverted into singlets in electroluminescence, despite a significant (~0.21 eV) singlet-triplet energy gap (ΔEST), in line with correlated quantum-chemical calculations, and a slow reverse intersystem crossing. We speculate that the lattice stiffness responsible for the narrow fluorescence and phosphorescence emission spectra also protects the triplets against non-radiative decay. An improved EQEmax of 21.1% for Mes3DIKTa compared to the parent DiKTa (14.7%) and, importantly, reduced efficiency roll- off compared to literature resonance TADF OLEDs, shows the promise of this design strategy for future design of R-TADF emitters for OLED applications.Publisher PDFPeer reviewe