Challenges and prospects in organic photonics

Challenges and prospects in organic photonics and electronics 6–8 November 2023 | Osaka, Japan

Faraday Discussions

Challenges and prospects in organic photonics and electronics 6–8 November 2023 | Osaka, Japan Book of Abstracts

Introduction

Challenges and prospects in organic photonics and electronics Faraday Discussion is organised by the Faraday Community for Physical Chemistry of the Royal Society of Chemistry This book contains abstracts of the posters presented at Challenges and prospects in organic photonics and electronics Faraday Discussion . All abstracts are produced directly from typescripts supplied by authors. Copyright reserved. Oral presentations and discussions All delegates at the meeting, not just speakers, have the opportunity to make comments, ask questions, or present complementary or contradictory measurements and calculations during the discussion. If it is relevant to the topic, you may give a 5-minute presentation of your own work during the discussion. These remarks are published alongside the papers in the final volume and are fully citable. If you would like to present slides during the discussion, please let the session chair know and load them onto the computer in the break before the start of the session. Faraday Discussion volume Copies of the discussion volume will be distributed approximately 6 months after the meeting. To expedite this, it is essential that summaries of contributions to the discussion are received no later than Wednesday 15 November for questions and comments and Wednesday 29 November for responses. Posters Posters have been numbered consecutively. The poster session will take place on Monday 6 November 2023 after the main sessions have ended. The posters will be available to view throughout the discussion during all refreshment breaks. During the dedicated poster session, authors should stand with their poster to discuss their research with other attendees.

Poster prize The Faraday Discussions poster prize will be awarded to the best student poster as judged by the committee.

Networking sessions There will be regular breaks throughout the meeting for socialising, networking and continuing discussions started during the scientific sessions.

Invited speakers

Scientific committee

Luisa Torsi Introductory Lecturer Università degli Studi di Bari, Italy

Youhei Takeda, Chair Osaka University, Japan Przemyslaw Data Lodz University, Poland Birgit Esser Ulm University, Germany Aiko Fukazawa Kyoto University, Japan

Hiroyuki Nishide Closing Remarks Lecturer Waseda University, Japan Youichi Tsuchiya Kyushu University, Japan Kunio Awaga Nagoya University, Japan

Peter Skabara Glasgow University, United Kingdom

Jenny Clark Sheffield University, United Kingdom

Natalie Stingelin Georgia Tech University/Imperial College London, United Kingdom

Xugang Guo Southern University of Science and Technology (SUStech), China Christine Luscombe Okinawa Institute of science and Technology, Japan

Nobuhiro Yanai Kyushu University, Japan

Rebeca Marcilla IMDEA Energy Institute, Spain

Nako Nakatsuka ETH Zurich, Switzerland

Bob Schroeder University College London, United Kingdom

Faraday Discussions Forum

www.rscweb.org/forums/fd/login.php

In order to record the discussion at the meeting, which forms part of the final published volume, your name and e-mail address will be stored in the Faraday Forum. This information is used for the collection of questions and responses communicated during each session. After each question or comment you will receive an e-mail which contains some keywords to remind you what you asked, and your password information for the forum. The e-mail is not a full record of your question. You need to complete your question in full on the forum . The deadline for completing questions and comments is Wednesday 15 November.

The question number in the e-mail keeps you a space on the forum. Use the forum to complete, review and expand on your question or comment. Figures and attachments can be uploaded to the forum. If you want to ask a question after the meeting, please e-mail faraday@rsc.org. Once we have received all questions and comments, responses will be invited by e-mail . These must also be completed on the forum . The deadline for completing responses is Wednesday 29th November. Please note that when using the Forum to submit a question or reply, your name and registered e-mail address will be visible to other delegates registered for this Faraday Discussions meeting. Key points: • The e-mail is not a full record of your comment/question. • All comments and responses must be completed in full on the forum Deadlines: Questions and comments Wednesday 15th November Responses Wednesday 29th November

With thanks to our Sponsors

Poster presentations

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Understanding the origin of thermally activated delayed fluorescence in coplanar emitters Katrina Bergmann University of British Columbia, Canada Simulating the spatiotemporal exciton dynamics in an electrically pumped organic laser Adam Bickerdike Durham University, UK Fabrication of CNT/polymer composite ribbons as flexible and lightweight heat conductors Naw Blessing Oo Nara Institute of Science and Technology, Japan Influential boron-oxygen interactions for blue emitters with high rate of reverse intersystem crossing Joseph Cameron University of Glasgow, UK Triplet-triplet spin interactions: understanding magnetic field effects on organic excitons Miles Collins UNSW Sydney, Australia Harvesting triplet states efficiently to produce energy efficient OLEDs Paloma dos Santos University of Sheffield, UK Synthesis of organotin (IV) compounds derived from schiff bases with potential applications in solar cells Arturo García-Zavala Facultad de Química UNAM, Mexico Spin dynamics of photo-excited quintet state in a parallel oriented acene dimer towards the application to a room temperature qubit Wataru Ishii Kyushu University, Japan

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Achievement of highly efficient and strong photoluminescence of Eu(III) complex in a host-guest film by triplet sensitization Shiori Miyazaki Kyushu University, Japan Development of porous polymer monolith showing Visible-to-UV photon upconversion towards flow photochemical reactions Sakura Nakagawa Kyushu University, Japan Deformable mechanoelectric generators based on electretized alkyl-π molecular liquids Takashi Nakanishi MANA, National Institute for Materials Science, Japan Thermoelectric measurements of multinuclear ruthenium alkynyl complexes Yuya Tanaka Tokyo Institute of Technology, Japan Influence of microstructural features on the synaptic behavior of polymer-based thin-film transistors Fu-Chiao Wu National Cheng Kung University, Chinese Taipei Synergetic H-bonding and C-T interaction mediated supramolecular polymers results in room temperature ferroelectrics and multiferroic materials Deepak Yadav Indian Institute of Science Education And Research Mohali, India Fluorosumanenes: unique building blocks for dielectric materials Yumi Yakiyama Osaka University, Japan Synthesis and charge transport properties of unsymmetrical meso- substituted tetrabenzoporphyrin derivatives Kazuya Miyazaki Nara Institute of Science and Technology, Japan Luminescence functionalization by composite of TICT process of aryl- modified carborane anions and countercations Takumi Yanagihara Kyoto University, Japan

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Impacts of methyl substituents on luminescence properties of NIR phosphorescent iridium(III) complexes with 2-phenylquinoxaline-based cyclometalated ligands Keima Yoneda Osaka Metropolitan University, Japan Improving the performance of a triboelectric nanogenerator by optimizing structural and electrical parameters of PDMS-based polymer films Qingyang Zhou Tokyo University of Science, Japan

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Understanding the origin of thermally activated delayed fluorescence in coplanar emitters Katrina Bergmann and Zachary M. Hudson The University of British Columbia, Canada

Materials that exhibit thermally activated delayed fluorescence (TADF) are important for applications in organic light-emitting diodes, light-emitting electrochemical cells, time-resolved fluorescence bioimaging, and photocatalysis. To improve the design of TADF emitters and accelerate conversion of triplet excitons to singlets, two principal techniques have been identified: (1) utilizing the heavy atom effect to increase spin orbit coupling, or (2) spatially separating the frontier molecular orbitals through orthogonal donor-acceptor design to minimize the singlet-triplet energy gap (∆E ST ). Planarized donor-acceptor materials exhibiting TADF have recently attracted attention due to their advantageous properties such as high colour purity, improved photostability, and high quantum yields, 1 but with large ∆E ST values and no heavy atoms, the origin of their TADF properties remains unclear. Our recent work on a pair of planar isomers that do and do not display TADF highlights the importance of modeling excited state potential energy surfaces of coplanar emitters to rationalize their photophysical behaviour. 2 However, a broader understanding of TADF in planar emitters is still missing. Herein, we investigate two sets of previously reported planar fluorophores: one set that exhibits TADF, and one set that does not. This theoretical investigation reveals trends that discernibly separate a variety of TADF emitters from non-TADF emitters, providing concrete metrics from which future planar emitters can be designed. References 1. I. Zoh, M. Imai-Imada, J. Bae, H. Imada, Y. Tsuchiya, C. Adachi and Y. Kim, J. Phys. Chem. Lett., 2021, 12 , 7512-7518. 2. K. Bergmann, R. Hojo and Z. M. Hudson, J. Phys. Chem. Lett., 2023, 14 , 310-317.

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Simulating the spatiotemporal exciton dynamics in an electrically pumped organic laser Adam Bickerdike, Roderick C.I. Mackenzie, Mujeeb U. Chaudhry Durham University, UK To reliably achieve electrically pumped organic lasers, a unified understanding of the complex interactions between charge carriers and excitons during LASER operation must be developed. The interplay between the large charge carrier densities required to reach threshold, and the respective excited state populations has been demonstrated to be a major problem in realising an electrically pumped organic laser (i.e., annihilation processes and quenching). In this work, a drift-diffusion model of a high current density µOLED device, utilising the PPV copolymer PDY-132 is developed. Importantly, the model includes the effect of charge carrier trapping through Shockley-Reed-Hall recombination and implements fundamental LASER theory to describe stimulated emission process. We demonstrate that the threshold for stimulated emission in a SY µOLED can be predicted based on the incorporation of carrier trapping in the device and simulating the effects of excited state absorption. References 1. Baldo, M.A., Holmes, R.J., Forrest, S.R.: Prospects for electrically pumped organic lasers. Physical Review B - Condensed Matter and Materials Physics 66(3), 353211–3532116 (2002) 2. Sandanayaka, A.S.D., Matsushima, T., Bencheikh, F., Terakawa, S., Potscavage, W.J., Qin, C., Fujihara, T., Goushi, K., Ribierre, J.C., Adachi, C.: Indication of current-injection lasing from an organic semiconductor. Appl. Phys. Express 12 (6), 061010 (2019) 3. Ahmad, V., Sobus, J., Greenberg, M., Shukla, A., Philippa, B., Pivrikas, A., Vamvounis, G., White, R., Lo, S.C., Namdas, E.B.: Charge and exciton dynam-ics of OLEDs under high voltage nanosecond pulse: towards injection lasing. Nature Communications 2020 11:1 11(1), 1–8 (2020)

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Fabrication of CNT/polymer composite ribbons as flexible and lightweight heat conductors Naw Blessing Oo, Nikita Kumari, Ryo Abe, Naofumi Okamoto, Manish Pandey, Hiroaki Benten, Masakazu Nakamura Nara Institute of Science and Technology, Japan With the increased utilization of electronic devices, their accelerating power densities lead to failure in electronic functions. Therefore, thermal reliability becomes more critical across such applications. Amongst the thermal management materials, carbon nanotubes (CNTs) are widely considered as they possess superior thermal conductivity ( κ ), chemical stability, and desirable elastic modulus [1]. However, typical κ values of CNT bulk materials are much lower than expected, probably due to the internal contact resistance between and randomly orientated CNT bundles. Recent studies have shown that shear-induced methods can prominently improve the alignment of CNTs [2], leading to an increase in κ of CNTs. We have also proposed a fabrication method of oriented CNT/polymer composite ribbons using the direct ink writing method via a robotic dispenser. In this work, factors influencing the κ of the CNT/polymer composite ribbon have been studied. The CNT dispersion was drawn on two types of substrates: hydrophilic bare glass and relatively hydrophobic poly(3-hexylthiophene-2,5-diyl) (P3HT)-coated glass with the optimized drawing parameters for CNT alignment such as the needle’s inner diameter ( φ ), the relative drawing speed ( RS ), the dispensing speed ( DS ) and the gap between the tip and the substrate ( d )as shown in Fig. 1. Free-standing CNT ribbons were then peeled off by immersing them in a methanol bath. The κ of the ribbon was evaluated using the cross-junction method, which is improved from the DC-heating T-junction method, proposed for the film-type materials [4]. It was found that as the CNT concentration decreases, the κ increases for both substrates. Besides, higher κ of CNT ribbon (~200 W/ mK) was observed on the bare glass substrate, while that on P3HT-coated glass was ~160 W/mK for the same optimum CNT concentration of 0.075% w/v. This can be attributed to the smaller ribbon thickness on the bare glass substrate than on the P3HT-coated glass (Fig. 2). The results will be discussed in detail on the poster.

References 1. B. Kumanek et al. J. Mater. Sci. 54, 7397-7427 (2019). 2. G. L. Goh et al. Adv. Mater. Interfaces 6, 1801318 (2019). 3. M. Pandey et al. Appl. Phys. Express 13, 065503 (2020). 4. R. Abe et al. J. Therm. Sci. 31, 1037 (2022).

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Influential boron-oxygen interactions for blue emitters with high rate of reverse intersystem crossing Joseph Cameron 1 , Suman Kuila 2 , Andrew P. Monkman 2 , Peter J. Skabara 1 1 University of Glasgow, UK, 2 Durham University, UK email: joseph.cameron@glasgow.ac.uk For the development of efficient organic light-emitting diode (OLED) displays, it is critical that the efficiency roll-off and device lifetime of blue OLEDs is improved. Emissive materials which undergo thermally activated delayed fluorescence (TADF) can efficiently harvest the triplet states that are generated in the emissive layer but devices using these materials typically have a lifetime of 100s of hours at best and exhibit efficiency roll-off. Therefore, it is imperative that new blue emitters are developed. The key to improving device lifetime and roll-off is to increase the rate of reverse intersystem crossing (rISC) and reduce radiative decay lifetimes as the excited state energy levels in blue emitters are close to the energy required for covalent bond dissociation. One method of increasing rISC is to achieve conformational control to avoid the presence of many different conformers, which causes slower radiative decay. 1 Nonetheless, it is also important that donor and acceptor units in emissive materials are not completely fixed to allow for rotational freedom for the vibrational coupling mechanism which is important for TADF. 2 Therefore, there is a balance to be struck between conformational control and constraining the molecule. Non-covalent interactions are a potentially effective means to achieve this difficult balance as such interactions are weak, yet significant enough to dictate conformation. In this work we present new blue emitter materials which feature influential boron-oxygen interactions. The impact of these interactions on molecular structure and the resulting physical properties will be discussed with X-ray crystallography data, cyclic voltammetry and photophysics studies presented. The boron-oxygen interactions strongly influence the photophysical properties, with the compound with most boron-oxygen contacts, CzOMe 2 BMes 2 , exhibiting the highest photoluminescence quantum yield (87%) of the series of emitters, with a rISC rate of ~10 6 s -1 . References

1. Eng J. et al. , J. Mater. Chem. C , 2019, 7 , 12942-12952 2. Ward J. S. et al. , Chem. Commun. , 2016, 52 , 2612-2615

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Triplet-triplet spin interactions: understanding magnetic field effects on organic excitons Miles I. Collins 1 , Francesco Campaioli 2 , Murad J. Y. Tayebjee 3 , Jared H. Cole 4 and Dane R. McCamey 1 1 School of Physics and ARC Centre of Excellence in Exciton Science, UNSW Sydney, Australia, 2 Padua Quantum Technologies Research Center, and Dipartimento di Fisica e Astronomia ‘G. Galilei’, Università degli Studi di Padova, Italy, 3 School of Photovoltaic and Renewable Energy Engineering, UNSW Sydney, Australia, 4 ARC Centre of Excellence in Exciton Science, School of Science, RMIT University, Australia Singlet fission and triplet-triplet annihilation (TTA) are photochemical energy conversion processes that occur with high efficiency in organic semiconductor materials. Singlet fission is the generation of two spin-correlated triplet excitons from a photo-generated singlet exciton, while TTA is the reverse - two triplet excitons can annihilate, via a spin-correlated pair-state, to create an emissive singlet exciton. Both processes have the potential to assist single-junction cells to exceed the thermodynamic limit in photovoltaics, and have other potential applications in nuclear hyper-polarisation, efficient blue LEDs, and optically addressable molecular qubits. The spin-interaction of the triplet exciton pair gives rise to many interesting phenomena, such as spin-2 'quintet' states formed from singlet fission, and magnetic field effects in the photoluminescence of TTA materials. Understanding these spin-interactions is an important step towards applying singlet fission and TTA in devices. Here we present recent theoretical and experimental results on the spin dynamics of triplet exciton pairs, including predictions about how time-varying exchange coupling between the triplet excitons can drive the formation of quintet states, and measurements of microscopic variation in the magnetic field effects in TTA-induced luminescence. References 1. Miles I Collins et al., Quintet formation, exchange fluctuations, and the role of stochastic resonance in singlet fission, Communications Physics, 6, 64, 2023.

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Harvesting triplet states efficiently to produce energy efficient OLEDs Paloma L dos Santos University of Sheffield, UK Organic light emitting diodes (OLEDs) have become a central part of materials research, with the ever-growing requirement for more energy efficient, high colour purity, higher quality display devices. There is significant interest in OLED materials which converts dark triplet excited states to emissive singlet states. Two mechanisms can harvest triplet states using metal-free organic molecules: (i) thermally activated delayed fluorescence (TADF) and (ii) triplet–triplet annihilation (TTA). In this poster I will present two studies, which showcases the latest advances on molecular control to enhance triplet harvesting in different classes of materials and their application in devices. The first study highlights how to achieve efficient reverse intersystem crossing and high colour purity in TADF materials. Via careful design of a new Multiresonant MR-TADF material (Mes3DiKTa) [1], aggregation formation was supressed (one of the main challenges on the MR-TADF field), even at high doping concentrations. This allowed us to produce devices that show high energy efficiency (External Quantum Efficiency above 20%) and narrowband emission (FWHM below 40 nm). The second study presents the first observation of TTA from columnar liquid crystalline state [2]. We show how careful mix of materials with complementary functions (ColLC-A and ColLC-B) can activate the TTA mechanism. Combination of the two molecules in blends yields TTA from ColLC-A dimers fuelled by the triplet population on ColLC-B dimers. Important, the observation of delayed fluorescence in the condensed viscous fluid state of liquid crystal materials, where molecules can be uniformly oriented by annealing, opens the possibility to use such materials as emissive layers of OLEDs to enhance light outcoupling as well as charge and exciton transport, achieving energy efficient devices. References 1. David Hall, Subeesh Madayanad Suresh, Paloma L. dos Santos, Eimantas Duda, Sergey Bagnich, Anton Pershin, Pachaiyappan Rajamalli, David B. Cordes, Alexandra M. Z. Slawin, David Beljonne, Anna Köhler, Ifor D. W. Samuel, Yoann Olivier, and Eli Zysman-Colman, Adv. Optical Mater. 2020, 8, 1901627 2. Larissa G. Franca, Paloma L. dos Santos, Piotr Pander, Marília G. B. Cabral, RodrigoCristiano, Thiago Cazati, Andrew P. Monkman, Harald Bock and Juliana Eccher, ACS Appl. Electron. Mater. 2022, 4, 7, 3486–3494

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Synthesis of organotin (IV) compounds derived from schiff bases with potential applications in solar cells Arturo García-Zavala, Oscar González-Antonio, Margarita Romero-Ávila,José Méndez- Stivalet and Norberto Farfán Facultad de Química, Universidad Nacional Autónoma de México, México The synthesis of three organotin (IV) compounds was carried out through a simple 'one-pot' reaction involving 7-hydroxycoumarin-8-carbaldehyde, diphenyl tin (IV) oxide, and the corresponding 2-aminophenol. Initially, they were subjected to an ultrasonic bath for 30 minutes, followed by continuous reflux for 12 hours using a Dean- Stark trap. Their geometries, frontier orbitals, and optical properties were calculated using the DFT approach. According to the computational results, frontiers orbitals indicate that these compounds could be tested in bulk heterojunction solar cells, however, variation in substituents in the 2-aminophenols allows for their potential application in dye-sensitized organic solar cells (DSSC) or bulk heterojunction (BHJ) cells.

References 1. Cantón-Díaz, A. M.; Muñoz-Flores, B. M.; Moggio, I.; Arias, E.; De León, A.; García-López, M. C.; Santillán, R.; Ochoa, M. E.; Jiménez-Pérez, V. M. One-Pot Microwave-Assisted Synthesis of Organotin Schiff Bases: An Optical and Electrochemical Study towards Their Effects in Organic Solar Cells. New J. Chem. 2018 , 42 (17), 14586–14596. https://doi.org/10.1039/ C8NJ02998A. 2. Monzón-González, C. R.; Sánchez-Vergara, M. E.; Vallejo Narváez, W. E.; Rocha-Rinza, T.; Hernández, M.; Gómez, E.; Jiménez-Sandoval, O.; Álvarez-Toledano, C. Synthesis and Characterization of Organotin(IV) Semiconductors and Their Applications in Optoelectronics. J. Phys. Chem. Solids 2021 , 150 , 109840. https://doi.org/10.1016/j.jpcs.2020.109840. 3. Sánchez Vergara, M. E.; Gómez, E.; Toledo Dircio, E.; Álvarez Bada, J. R.; Cuenca Pérez, S.; Galván Hidalgo, J. M.; González Hernández, A.; Hernández Ortega, S. Pentacoordinated Organotin(IV) Complexes as an Alternative in the Design of Highly Efficient Optoelectronic and Photovoltaic Devices: Synthesis and Photophysical Characterization. International Journal of Molecular Sciences . 2023 . https://doi.org/10.3390/ijms24065255.

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Spin dynamics of photo-excited quintet state in a parallel oriented acene dimer towards the application to a room temperature qubit Wataru Ishii 1 , Masaaki Fuki 3 , Eman M Bu Ali 4 , Samara Medina 4 , Shunsuke Sato 5 , Bhavesh Parmar 1 , Reiya Yabuki 1 , Akio Yamauchi 1 , Yasuhiro Kobori 3 , Jenny Clark 4 , Go Watanabe 5 and Nobuhiro Yanai 1,2 1 School of Eng., Kyushu University, Japan, 2 JST FOREST, Japan, 3 Kobe University, Japan, 4 Sheffield University, UK, 5 Kitasato University, Japan Spin is one of the degrees of freedom with quantum properties and is a promising candidate for quantum bits (qubits). Electron spins in molecules have attracted particular attentions as qubits because the spin degrees of freedom can be modulated by molecular design. To achieve the quantum operations, the generation of the pure quantum state, which is called “initialization”, is required. The quintet excitons generated through singlet fission (SF) seem promising as novel qudits. Since quintets have been theoretically proved to be selectively distributed to specific sublevels by controlling parallel orientation between molecules 1 , they are expected to become optically addressable qudits. In this study, we synthesized a schiff base-bridged parallel-oriented pentacene dimer and evaluated the quintet excitons generated through SF. Single-crystal X-ray diffraction measurements revealed that the two pentacene units in the dimer was orientated in parallel (Fig.1) . Molecular dynamics (MD) simulation implied the parallel orientation of the pentacene dimer could be maintained even at room temperature. Then femtosecond transient absorption (fsTA) spectroscopy confirmed that SF occurred in the diluted pentacene dimer solution. Transient ESR (TRESR) were performed on the pentacene dimer dissolved in polystyrene at room temperature (Fig. 2) . It revealed the selective population among the quintet sublevels, which implies the potential of the pentacene dimer as room temperature qudit. The correlation between the orientation between two pentacene units and the population among the quintet sublevels revealed by the results of simulations will be discussed.

References 1. Smyser, K. E.; Eaves, J. D. Singlet fission for quantum information and quantum computing: the parallel JDE model. Scientific Reports 2020 , 10 (1)

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Achievement of highly efficient and strong photoluminescence of Eu(III) complex in a host-guest film by triplet sensitization Shiori Miyazaki 1 , Kiyoshi Miyata 1 , Kenichi Goushi 2 , Yuichi Kitagawa 3,4 , Yasuchika Hasegawa 3,4 , Chihaya Adachi 2 , Ken Onda 1 1 Department of Chemistry, Kyushu University, Japan, 2 OPERA, Kyushu University, Japan, 3 Faculty of Engineering, Hokkaido University, Japan, 4 WPI-ICReDD, Hokkaido University, Japan Trivalent lanthanide (Ln(III)) complexes are expected to be used as light-emitting materials, such as organic light emitting diodes (OLEDs), because of their high color purity.[1] Nonetheless, they are hindered by the inherent limitation of their small absorption coefficient. To address this challenge arising from the forbidden f-f transitions, extensive efforts have been dedicated to creating efficient photoluminescent Ln(III) complexes.[2] These efforts center around molecular technology, aiming to achieve effective energy transfer from antenna ligands to Ln(III) ions while ensuring robust light absorption by the antenna ligands. However, the advancement of antenna ligands capable of sensitization is hampered by difficulties in precisely controlling the coordination structures of lanthanides. In this study, we have overcome this challenge through a straightforward approach employing solution- processed host-guest films. Specifically, we achieved sensitization of trivalent europium (Eu(III)) via triplet exciton through host-molecule-based mechanisms. In comparison to conventional luminescent Eu(III) complexes, our system comprising host molecules of mT2T (2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine) and Eu(hfa) 3 (TPPO) 2 (hfa: hexafluoroacetylacetonato, TPPO: triphenylphosphine oxide) as guest components exhibited a remarkable enhancement in overall photoluminescence intensity ( I PL ). Notably, we achieved a 500-fold increase in I PL compared to a typical Eu(III) complex with a standard ligand. To delve into the source of this relatively high I PL , we employed time-resolved photoluminescence spectroscopy (TR-PL) and femtosecond transient absorption spectroscopy (fs-TAS) across a wide temporal range spanning from sub-picoseconds to hundreds of microseconds. This comprehensive investigation shed light on the emission mechanisms within the host-guest film. Starting from the initial excitation of host molecules and culminating in the emission of the Eu(III) complex, we elucidated the stepwise processes within the film: (1) intersystem crossing (ISC) within the host molecule, (2) inter-molecular energy transfer from host molecules to ligands of the Eu(III) complex, (3) intra-molecular energy transfer from ligands to Eu(III) ions, and (4) emission processes involving f-f transitions in Eu(III). Notably, we discovered that the efficiencies of all energy transfer processes (1)-(3) are nearly perfect, and the efficiency of the Eu(III) emission process (4) dictates the overall quantum yield of the film. This remarkable photoluminescence efficiency is attributed to ideal triplet sensitization processes, whereby the swift and effective ISC in mT2T results in efficient triplet–triplet inter-molecular energy transfers with minimal losses.[3] Ultimately, our findings propose well-defined design strategies for efficient light harvesting of Eu(III) complexes. This entails a host-guest system featuring host molecules that (1) exhibit efficient ISC and (2) possess triplet state energies aligned with those of the ligands in the Eu(III) complex. Our discovery opens the pathway for achieving efficient light harvesting in Eu(III) complexes through a straightforward fabrication process utilizing solution

processing. References 1. L. Wang, et al ., Adv. Optical Mater. 2019 , 7 , 1801256. 2. J.-C. G. Bünzli, Chem. Rev. 2010 , 110 , 5, 2729. 3. S. Miyazaki et al. , Chem. Sci. 2023 , 14 , 6867.

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Development of porous polymer monolith showing Visible-to-UV photon upconversion towards flow photochemical reactions Sakura Nakagawa 1 , Naoto Matsumoto 2 , Masanori Uji 2 , Kazuyoshi Kanamori 3,6 , Kazuki Nakanishi 4,5 , Nobuhiro Yanai 2,7 1 School. of Eng., Kyushu University, Japan, 2 Grad. School. of Eng., Kyushu University, Japan, 3 Grad. School. of Sci., Kyoto University, Japan, 4 IMaSS, Nagoya University, Japan, 5 iCeMS, Kyoto University, Japan, 6 PRESTO, JST, Japan, 7 FPREST, JST, Japan While ultraviolet (UV) light is useful in driving various photochemical reactions, it is impractical because of the limited UV sources and reaction vessels. Triplet-triplet annihilation-based photon upconversion (TTA-UC) is one of the methods to generate UV light from visible light. [1] However, photoreactions using UC from visible to UV light have only been reported in solution systems, and the development of solid materials has been desired for more practical use. In this work, we report on the development of porous polymer monolith that exhibits TTA-UC from visible to UV light for application to flow photochemical reactions (Fig. 1a). The monolith is a porous material with µm-scale co-continuous structures, enabling the use of flow systems. It was synthesized by polymerizing styrene dissolving CBDAC (donor) and TIPS-Nph (acceptor) [2] by using silica monolith as a template. [3] After template removal, the formation of co-continuous structures was observed. The UC emission with the peak top of 376 nm was obtained when a CW laser of 445 nm was irradiated to the chromophore-doped polystyrene monolith (Fig. 1b).

Fig.1 (a) Schematic diagram of porous polymer monolith for flow photochemical reactions. (b) Photoluminescence spectra of CBDAC and TIPS-Nph doped in polystyrene monolith at various excitation intensities (λ ex = 445 nm, 425 nm short-pass filter). References

1. M. Uji, et al., Ang. Chem. Int. Ed ., 2023 , 62, e202301506 2. M. Uji, et al., J. Mater. Chem. , C, 2022 ,10, 4558-4562 3. K. Nakanishi, et al., J. High Resol. Chromatogr. , 2000 , 23, 106-110

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Deformable mechanoelectric generators based on electretized alkyl-π molecular liquids Takashi Nakanishi MANA, National Institute for Materials Science, Japan Energy harvesting systems with lightweight, small size, excellent stretchability/deformability, as well as a large and stable power generation would be ideal wearable soft electronic devices applicable for future remote medical systems, healthcare, and robotics applications. For these demands, liquid electrets which possess high deformability, excellent processability, and maintain trapped electrostatic charges in the liquids can be the potential substances. Liquid electrets in which π-conjugated molecular/polymer units are wrapped with bulky yet flexible branched-alkyl chains were developed. Interestingly, electrostatic charges are trapped and retained in the liquid. Stretchable/deformable mechanoelectric generators capable of being stretched up to 300% were constructed with those liquid electrets. In addition, the device could adapt the frequencies in the range of the human body motion below 50 Hz. References 1. A. Ghosh et al., Nature Commun. , 10 , 4210 (2019). 2. A. Shinohara, M. Yoshida, C. Pan, T. Nakanishi, Polym. J. , 55 , 529-535 (2023). 3. R. K. Gupta, M. Yoshida, A. Saeki, Z. Guo, T. Nakanishi, Mater. Horiz. , in press (2023), DOI: 10.1039/D3MH00485F. 4. A. Tateyama, T. Nakanishi, Responsive Mater. , in press (2023), DOI: 10.1002/rpm.20230001.

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Thermoelectric measurements of multinuclear ruthenium alkynyl complexes

Yuya Tanaka , 1 Sohyun Park, 2 Jiung Jang, 2 Hyo Jae Yoon 2 1 Tokyo Institute of Technology, Japan, 2 Korea University, Korea

Molecules with high Seebeck coefficients ( S ) have potential applications in thermoelectric materials. However, their S values at single-molecule and self-assembled monolayer levels are low partly due to large energy gaps ( E – E F ) between molecular frontier orbital energy and Fermi energy of the electrodes. We have recently reported highly conducting organometallic molecules with electron-rich ruthenium tetraphosphine fragments in molecular junction. 1 The theoretical study suggests that their small energy gaps ( E – E F ), which may lead to a large Seebeck coefficient. In this study, we report the Seebeck coefficient of multinuclear ruthenium complexes bridged by p -diethynylbenzene-diyl linkers and examine their thermoelectric properties. 2 Thermoelectric measurements for mono-, di- and tri-ruthenium complexes 1 R - 3 R (R = H, CF 3 , OMe) were conducted using the Au-molecule-EGaIn/Ga 2 O 3 system. 3 Upon heating the gold electrode, the S values increased with the number of metal fragments, and the trinuclear complex showed a value exceeding 70 µV/K, which is the highest S value obtained by SAM junction reported so far. Theoretical calculations and cyclic voltammograms indicate that the high Seebeck coefficient is caused by the high-lying HOMO, which destabilizes as the number of metal fragments increases. We also examined substituents effect for the dinuclear complexes ( 2 R ). References 1. M. Akita, Y. Tanaka, Coord. Chem. Rev. 2022 , 461 , 214501. 2. S. Park, J. Jang, Y. Tanaka, H. J. Yoon, Nano Lett. 2022 , 22 , 9693. 3. Nijhuis, C. A.; Reus, W. F.; Barber, J. R.; Dickey, M. D.; Whitesides, G. M. Nano Lett. 2010 , 10 , 3611.

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Influence of microstructural features on the synaptic behavior of polymer-based thin-film transistors Fu-Chiao Wu, Chun-Yu Chen, Wei-Yang Chou, Horng-Long Cheng National Cheng Kung University, Taiwan In this study, poly(3-hexylthiophene) (P3HT) as the active layer is used to fabricate ion-gel-gated thin-film transistors. Various methods are adopted to grow P3HT thin films, including spin-coating with thermal annealing (ST), spin-coating with solvent annealing (SS), and drop-casting with solvent annealing (DS). The DS and SS devices produce the largest and lowest drain current ( I D ), respectively. Compared with the ST and SS devices, the DS device has smaller subthreshold swing, indicating the existence of lower interfacial trap density. In the X-ray diffraction (XRD) patterns of various P3HT thin films, only the DS specimen has high-order diffraction peaks. Based on the information of XRD patterns, the DS specimen has the shortest d -spacing and the largest crystalline size, and the ST specimen has the longest d -spacing and the smallest crystalline size. These results indicate that the DS specimen possesses compact lamellar stacking and better crystalline structures, leading to a higher I D of the DS device. Although the microstructures of the SS specimen are better than those of the ST specimen, the ST device performs a larger I D than the SS device. For the SS device, during solvent annealing of P3HT, the underlying poly(methyl methacrylate) (PMMA, buffer layer) could permeate into P3HT and near the channel region. Those insulating PMMA can hinder charge transport, resulting in a lower I D of the SS device than the ST device. The synaptic behavior of different P3HT-based devices is investigated. The ST and DS devices produce increased excitatory postsynaptic current (EPSC)with increasing spike (gate bias) time, performing a synaptic potentiation behavior. The EPSC increment of the DS device is greater than that of the ST device, resulting from better microstructures and lower interfacial trap density of the DS device. Surprisingly, the SS device performs decreased EPSC with increasing spike time, showing a synaptic depression behavior. During the stimulation of a spike, holes could be captured by the PMMA near the channel region. Those captured holes can impede hole accumulation and hole transport. Hence, the increased spike time poses reduced EPSC of the SS device. During a paired-pulse stimulation, the EPSC of the ST and DS devices under the second pulse is higher than that under the first pulse, showing a paired-pulse facilitation (PPF) behavior. Compared with the ST device, the DS device has a larger PPF index because of the lower interfacial trap density and better microstructures. Interestingly, the SS device produces lower EPSC under the second pulse than the first pulse, performing a paired-pulse depression behavior. This behavior results from the suppressed hole transport and accumulation caused by the captured holes in PMMA. In addition, with an additional planar gate electrode, these P3HT-based devices can act as YES, OR, and XOR logic gates.

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Synergetic H-bonding and C-T Interaction mediated supramolecular polymers results in room temperature ferroelectrics and multiferroic materials Yadav Deepak 1 , Zinnia Mallick 2 , Dalip Saini 2 , Dipankar Mandal *2 and Raj Kumar Roy *1 1 Indian Institute of Science Education and Research Mohali, India, 2 Institute of Nano Science and Technology, India Ferroelectrics are materials with inherent polarization that can be reversed by an external electric field and show distinct pyroelectric and piezoelectric properties which offer promising applications in artificial intelligence, self- powered sensors, wearable electronics, and biomedical devices. 1 Furthermore, research interest has focused on multiferroic materials, which can exhibit multiple ferroic orders like ferroelectricity, ferromagnetism, and ferroelasticity. The cross-coupling between these order states means the ability to control magnetism via an electric field or vice versa termed as magnetoelectric effect 2 (ME) which makes them a potential candidate for various applications. Both ferroelectric and multiferroic materials developed from inorganic metals which have excellent properties in terms of either polarization or magnetization, but the presence of toxic and rare earth metals raises a great concern. In contrast, organic materials possess several highly desirable attributes for emerging technologies, including their lightweight nature, flexibility, cost-effectiveness, solution-processability, non-toxicity, and ease of integration into devices. Such limitations necessitate to development of new soft organic materials. In my presentation, I will describe the design of supramolecular polymers that will serve the purpose of ferroelectric and multiferroic at room temperature in bulk state. The supramolecular scaffold is based on the 1,3,5- benzene tricarboxamide and functionalized with electron-deficient unit naphthalene diimide (NDI) at the periphery of three arms (BTA-C 6 -NDI 3 ) which can be able to intercalate an electron-rich guest molecule through charge transfer interaction. The C-T mediated 1-D hierarchical structure results in gelation and shows ferroelectric behavior and room temperature with Tc ~ 47 °C. The piezoelectric and pyroelectric responses observed in the organogel network suggest potential applications in mechanical, and thermal energy harvesting. 3 Next, an organic radical spin (magnetic domain) was precisely incorporated through covalent linkage in a similar scaffold which shows ferroelectric and ferromagnetic phases at room temperature. Due to piezoelectric response, magnetostriction arises which facilitates the magnetoelectric coupling ME (a~220 mV/Oe cm). 4

References 1. Cao, X.; Xiong, Y.; Sun, J.; Zhu, X.; Sun, Q.; Wang, Z. L. Adv. Funct. Mater. 2021 , 31 , 2102983 2. Curie, J. Phys. Théorique Appliquée 1894 , 3 , 393–415. 3. Deepak, Z. Mallick, U. Sarkar, D. Mandal, R. K. Roy, Chem. Mater. 2023 , 35 , 3316-3328 4. Deepak, D. Saini, D. Mandal, R. K. Roy, (Manuscript under preparation)

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Fluorosumanenes: unique building blocks for dielectric materials Yumi Yakiyama 1,2 , Minghong Li 1 , Dongyi Zhou 1 , Chisato Sato 3 , Kohei Sambe 3 , Tomoyuki Akutagawa 3,4 , Teppei Matsumura 5 , Nobuyuki Matubayashi 5 , Hidehiro Sakurai 1,2 1 Division of Applied Chemistry, Graduate School of Engineering, Osaka University, Japan, 2 Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Osaka University, Japan, 3 Graduate School of Engineering, Tohoku University, Japan, 4 Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Japan, 5 Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Japan Sumanene ( 1 ) is one of the representative buckybowls and is known to show unique properties such as bowl inversion behaviour derived from its unique bowl shape [1]. Especially 1 affords unidirectionally arraigned π-stacking columns in the solid state [2]. However, this nature also makes the bowl inversion behaviour of 1 useless for the induction of dielectric response in the solid state. In this context, we instead focused on the in-plane motion of sumanene skeleton in its columnar structure and attempted to utilize this motion to bring out the dielectric response ( Figure ). In this work, we designed and synthesized new fluorinated sumanene families and investigated their solid state dielectric properties. The representative one, difluorosumanene ( 2 ) possesses two fluorine atoms on the same benzylic carbon of pristine sumanene to have a large dipole moment along the in-plane direction. Thermal analyses, variable temperature X-ray diffraction and IR measurements indicated the presence of in-plane motion of 2 although no clear phase transition was involved [3]-[6]. This thermal property of 2 realized an anisotropic dielectric response with a Debye-type dielectric relaxation in the single crystalline state. In addition, recently synthesized monofluorinated sumanene ( 3 ) was also investigated. Fluorine atom on the benzylic carbon of 3 has two different geometry, the outer ( exo ) and the inner ( endo ) sides of the bowl and therefore the two diastereomers show large difference in their dipole moments. We recently found that these diastereomers were convertible via bowl flipping motion in the solution state and that its exo-endo ratio in the crystalline state was controllable, showing significant difference in their dielectric responses.

References 1. Sakurai, H., Daiko, T., Hirao , T. Science 301 , 1878. 2. Mebs, S., Weber, M., Luger, P., Schmidt, B. M., Sakurai, H., Higashibayashi, S., Onogi, S., Lentz, D. (2012). Org. Biomol. Chem. 10 , 2218. 3. Li, M., Wu, J.-Y., Sambe, K., Yakiyama, Y., Akutagawa, T., Kajitani, T., Fukushima, T., Matsuda, K., Sakurai . H. (2022). Mater Chem Front. 6 , 1752. 4. Li, M., Chen, X., Yakiyama, Y., Wu, J., Akutagawa, T., Sakurai, H . (2022). Chem. Commun. 58 , 8950. 5. Yakiyama, Y., Li, M., Sakurai, H . (2023). Pure Appl. Chem. 95 , 421. 6. Yakiyama, Y., Li, M., Zhou, D., Abe, T., Sato, C., Akutagawa, T., Matsumura, T., Matubayashi, N., Sakurai, H. ChemRxiv 2023 , DOI: 10.26434/chemrxiv-2023-dt8kb

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Synthesis and charge transport properties of unsymmetrical meso-substituted tetrabenzoporphyrin derivatives Kazuya Miyazaki 1 , Kyohei Matsuo 2 , Naoki Aratani 1 , Hiroko Yamada 2 1 Nara Institute of Science and Technology, Japan, 2 Institute for Chemical Research, Kyoto University, Japan One of the key issues in the development of organic field-effect transistor (OFET) materials is the improvement of charge mobility. Since charge mobility depends on intermolecular interactions in solid state, it is important to control the crystal structure. The current mainstream OFET materials such as acenes and heteroacenes have one-dimensionally (1D) extended polycyclic aromatic frameworks, and the effect of substitution on the crystal structure has been intensively studied. However, molecular design strategy to control the crystal structure of two- dimensionally (2D) p-extended organic semiconductor has not been intensively explored. Tetrabenzoporphyrin (TBP) is a useful building block as an organic semiconductor due to its chemical stability, large absorption coefficient in visible region, and strong p-stacking interaction. We previously synthesized 5,15-bis(triisopropylsilylethynyl)tetrabenzoporphyrin (TIPS-TBP) and its metal complexes [1,2]. TIPS-TBP shows excellent OFET properties with a maximum hole mobility of 1.1 cm 2 V –1 s –1 , when it takes the 2D brickwork packing structure [3]. However, most of its analogues formed 1D columnar structure, which generally exhibits lower hole mobilities in the thin film FETs. In our previous studies, we succeeded in controlling its polymorphism by optimizing the substituents and deposition condition [4,5], but the crystal structure control of TBP by structural modification remained a challenge. In this study, we synthesized an unsymmetric meso-substituted TBP derivative and its zinc(II) complex to demonstrate the effect of molecular symmetry on the crystal packing. Both compounds showed identical crystal structures and formed 2D herringbone-like packing structures consisting of slipped p-stacking with an antiparallel manner in the crystal. This result is in contrast to the fact that the crystal structure of the symmetric TIPS-TBP is altered by the introduction of central metals [4]. Unsymmetric molecular structure would make 2D p-stacking more stable than 1D columnar structure to counteract steric and electronic imbalance in the crystal. OFETs using unsymmetric TBP derivative and zinc complex achieved the maximum hole mobility of 0.71 and 0.55 cm 2 V –1 s –1 , respectively. These mobilities are superior to those of thin films of TIPS-BP in 1D columnar packing, and comparable to that in 2D brickwork packing. References 1. Takahashi, K.; Kuzuhara, D.; Aratani, N.; Yamada, H. J. Photopolym. Sci. Technol. 2013, 26, 213–216. 2. Takahashi, K.; Yamada, N.; Kumagai, D.; Kuzuhara, D.; Suzuki, M.; Yamaguchi, Y.; Aratani, N.; Nakayama, K.; Yamada, H. J. Porphyrins Phthalocyanines 2015, 19, 465–478. 3. Takahashi, K.; Shan, B.; Xu, X.; Yang, S.; Koganezawa, T.; Kuzuhara, D.; Aratani, N.; Suzuki, M.; Miao, Q.; Yamada, H. ACS Appl. Mater. Interfaces 2017, 9, 8211–8218. 4. Zhu, J.; Hayashi, H.; Chen, M.; Xiao, C.; Matsuo, K.; Aratani, N.; Zhang, L.; Yamada, H. J. Mater. Chem. C 2022, 10, 2527–2531. 5. Jeong, E.; Ito, T.; Takahashi, K.; Koganezawa, T.; Hayashi, H.; Aratani, N.; Suzuki, M.; Yamada, H.; ACS Appl. Mater. Interfaces 2022, 14, 32319–32329.

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Luminescence functionalization by composite of TICT process of aryl-modified carborane anions and countercations Takumi Yanagihara and Kazuo Tanaka Kyoyo University, Japan Introduction In recent years, ortho -carborane ( o C ; the upper figure) has attracted a great deal of attention as a scaffolding framework for luminescent materials. [1] When aromatic compounds (Ar), such as pyrene, anthracene, are connected at the carbon atom in the carborane unit, intense emission can be observed from the twisted intramolecular charge transfer (TICT) in the solid state by o C working as an electron-accepting unit. By using this unique TICT emission, it is expected to be an excellent light-emitting functional material. By the way, the family of carboranes involves various structures other than o C with different number of vertices and carbon atoms. Utilization of its diverse skeletons may lead to further functionalization of light-emitting materials.In this research, we paid particular attention to nido -carborane anion ( n CA ), which is obtained by deboronation from o C with strong nucleophiles (the upper figure). By elucidating the photophysical process of Ar-substituted n CA ( Ar- n CA ), we aimed to develop further functionality of fluorescent materials using carborane. [2] Results and Discussion We synthesized Ar- n CA and succeeded in introducing five kinds of counter cations (NMe 4 + , NEt 4 + , NBu 4 + , PPh 4 + , and K + ).Photoluminescence spectra of Ar- n CA in various solvents (1.0×10 –5 M) showed two peaks: One is from locally excited (LE) emission around 400 nm, the other is from TICT emission around 500–550 nm. In the TICT process, π-plane rotates from perpendicular to parallel orientation along the C–C bond in the carborane unit in the excited state. At this process, n CA acts as an electron-donating unit. It is surprising that luminescence species changed by counter cations in nonpolar solvents (chloroform and toluene). When the counter cation was NBu 4 + , Ar- n CA showed TICT emission, whereas it was PPh 4 + , Ar- n CA showed LE emission. This drastic change should be stemmed from the difference in the interaction between Ar- n CA and counter cations. NBu 4 + should interact with Ar unit of Ar- n CA , while PPh 4 + might interact with the carborane unit. Therefore, in the case of PPh 4 + , the electron-donating ability might be weakened through charge cancellation, followed by the LE emission. This electrostatic interaction might be explained by the HSAB theory. The peculiar TICT process described above also occurs in the solid state (the lower-left figure). Ar- n CA is extremely useful as a stimuli-responsive material because the degree of rotation of the π-plane can be controlled according to the external environment of the molecule, such as temperature and crystallinity. When a pristine crystalline sample was ground until it became amorphous, the emission wavelength shifted to the longer wavelength region. The result of the variable temperature PL spectra indicates that the amorphization allowed the rotation of the π-plane. The ground sample can be annealed back to its original crystalline state. Furthermore, this unique stimuli-responsivity can be controlled by counter cations (the lower-right figure). From these results, we believe that Ar- n CA works as an excellent anion-based emitter.

References 1. Ochi, J.; Tanaka, K.; Chujo, Y. Angew. Chem. Int. Ed. 2020 , 59 , 9841–9855. 2. Yanagihara, T.; Tanaka, K. Adv. Opt. Mater. 2023 , 2300492.

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