A5084319082- Organic Light-Emitting Diodes Research
- Organic Electronics and Photovoltaics
- Luminescence and Fluorescent Materials
- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Conducting polymers and applications
- Lanthanide and Transition Metal Complexes
- Perovskite Materials and Applications
- Electron Spin Resonance Studies
- Crystallography and molecular interactions
- Magnetism in coordination complexes
- Photochemistry and Electron Transfer Studies
- Molecular Junctions and Nanostructures
- Molecular Sensors and Ion Detection
- Quantum Dots Synthesis And Properties
- Synthesis and Properties of Aromatic Compounds
- Spectroscopy and Quantum Chemical Studies
- Strong Light-Matter Interactions
- Photoreceptor and optogenetics research
- Nanocluster Synthesis and Applications
- Photonic Crystals and Applications
- Porphyrin and Phthalocyanine Chemistry
- Quantum-Dot Cellular Automata
- Advanced biosensing and bioanalysis techniques
- Organoboron and organosilicon chemistry
Osaka University
2022-2025
RIKEN Center for Emergent Matter Science
2019-2022
Kyushu University
2005-2021
Japan Science and Technology Agency
2018-2021
RIKEN
2021
Wako University
2019
Kawaguchi Junior College
2019
Aomori University
2017-2019
Yamagata University
2011-2015
NTT (Japan)
2005
Abstract Thermally activated delayed fluorescence (TADF) materials, which enable the full harvesting of singlet and triplet excited states for light emission, are expected as third‐generation emitters organic light‐emitting diodes (OLEDs), superseding conventional phosphorescence materials. High photoluminescence quantum yield ( Φ PL ), narrow‐band emission (or high color purity), short lifetime all strongly desired practical applications. However, to date, no rational design strategy TADF...
Concentration quenching of thermally activated delayed fluorescence is found to be dominated by electron-exchange interactions, as described the Dexter energy-transfer model. Owing short-range nature even a small modulation in molecular geometric structure drastically affects concentration-quenching, leading enhanced solid-state photoluminescence and electroluminescence quantum efficiencies.
Abstract Hund’s multiplicity rule states that a higher spin state has lower energy for given electronic configuration 1 . Rephrasing this molecular excited predicts positive gap between spin-singlet and spin-triplet states, as been consistent with numerous experimental observations over almost century. Here we report fluorescent molecule disobeys negative singlet–triplet of −11 ± 2 meV. The inversion the singlet triplet results in delayed fluorescence short time constants 0.2 μs, which...
Thermal equilibration between singlet and triplet excited states achieves high-performance pure organic light-emitting diodes.
Abstract Reverse intersystem crossing (RISC), the uphill spin-flip process from a triplet to singlet excited state, plays key role in wide range of photochemical applications. Understanding and predicting kinetics such processes vastly different molecular structures would facilitate rational material design. Here, we demonstrate theoretical expression that successfully reproduces experimental RISC rate constants ranging over five orders magnitude twenty molecules. We show spin flip occurs...
Theoretical and experimental studies since the 1980s have pointed to existence of organic molecules that violate Hund's rule maximum multiplicity, with lowest singlet excited state having lower energy than triplet state. With rising prevalence light-emitting diodes (OLEDs) in display technology, these types are being investigated as a new class emitters. The singlet–triplet inversion implies thermal activation is not necessary achieve fast harvesting, providing potential benefits over...
Multi-organic light-emitting devices comprising two units stacked in series through a charge-generation layer are fabricated by solution processes. A zinc oxide nanoparticles/polyethyleneimine bilayer is used as the electron-injection and phosphomolybdic acid layer. Appropriate choice of solvents during spin-coating each ensures nine-layered structure
Poly(N-vinylcarbazole) undergoes cross-linking to highly solvent-resistant films through an oxidative coupling reaction, for which annealing process takes only 3 min at 110 °C. This reaction allows the construction of a solution-processed multilayer OLED without time-consuming process. The maximum external quantum efficiency reaches 18%, and remains 17%, even high brightness 10 000 cd m(-2) all-solution-processed blue OLEDs.
Significant efforts have been devoted to the development of novel efficient blue-emitting molecules for organic light-emitting diode (OLED) applications. Blue emitters exhibiting thermally activated delayed fluorescence (TADF) potential achieve ∼100% internal electroluminescence quantum efficiency in OLEDs. In this paper, we report a promising molecular design strategy obtaining appropriate high singlet and triplet excited energies, short exciton lifetimes, efficiencies blue TADF emitters....
Functional organic materials that display reversible changes in fluorescence response to external stimuli are of immense interest owing their potential applications sensors, probes, and security links. While earlier studies mainly focused on photoluminescence (PL) color stimuli, stimuli-responsive electroluminescence (EL) has not yet been explored for color-tunable emitters light-emitting diodes (OLEDs). Here a fluorophoric molecular system is reported capable switching its emission between...
Full-color all-organic optical upconversion devices that can directly convert incident near-infrared (NIR) light into tunable visible were developed by integrating an organic light-emitting diode (OLED) on NIR-sensitizing photodetector. Thermally activated delayed fluorescence (TADF) emitters utilized for the first time in achieving high electroluminescence (EL) efficiency OLED unit and overall efficiency. The emission color of EL be varied across entire region ranging from blue to red white...
Thermally activated delayed fluorescence (TADF) materials generate energetically equivalent spin-singlet and spin-triplet excited states. In the presence of an energy acceptor, each state undergoes transfer on different length scales. However, lack quantitative understanding dependence energy-transfer processes hampers rational design molecular systems that control exciton transport in organic light-emitting diodes (OLEDs) using TADF. We herein utilize a dendritic fluorophore G1, which...
Molecular organic fluorophores are currently used in light-emitting diodes, though non-emissive triplet excitons generated devices incorporating conventional limit the efficiency. This can be overcome materials that have intramolecular charge-transfer excitonic states and associated small singlet-triplet energy separations; triplets then converted to emissive singlet resulting efficient delayed fluorescence. However, mechanistic details of spin interconversion not yet been fully resolved. We...
Deep-blue thermally activated delayed fluorescence materials based on dibenzo-fused phosphacycles are developed.
Organic emitters exhibiting delayed fluorescence (DF) are promising luminescent materials for next-generation organic light-emitting diodes (OLEDs). Faster intersystem crossing rates and shorter emission lifetimes can be achieved in molecules through the incorporation of heavy atoms, which enhance spin–orbit coupling promote between singlet triplet states. DF often contain a sulfur atom, reports selenium-containing OLEDs also exist. However, literature lacks direct exploration effect on...
We show a growth of high-quality thin films wide bandgap semiconductor copper iodide (CuI) on Al2O3 substrates by molecular beam epitaxy. Employing buffer layer deposited at lower temperature (160 °C) prior to the main growth, maximum is elevated up 240 °C, resulting in significant improvement crystallinity as verified sharp x-ray diffraction peaks well step-and-terrace structure observed atomic force microscopy. Optimum more intense free exciton emission photoluminescence spectra than...
Light-emitting molecules have been extensively studied due to their potential and wide variety of applications from optoelectronic devices biomedical applications. To fully understand rationalize the light-emitting process for innovation next-generation applications, it is vital reveal dynamic behavior excitons, where excited electronic states (locally excited, charge transfer, separated states), spin multiplicity, motion atomic nucleus are interacting each other. Here, we will show our...
Spin conversion in molecular excited states is crucial for the development of next-generation optoelectronic devices.