Topics

Research 01

Hyperfluorescence

Hyperfluorescence, a cutting-edge emission concept, has emerged as a promising contemporary solution for next-generation organic light-emitting diodes (OLEDs). It offers the potential to simultaneously achieve high efficiency, stability, brightness, and color purity in OLED displays. In general, hyperfluorescence is a three-component system consisting of a host matrix, thermally activated delayed fluorescence (TADF) donor, and fluorescent acceptor. Fundamentally, the primary role of the host matrix is to suppress concentration quenching and aggregation of the TADF donors as well as Dexter transfer of triplets from the donor to the acceptor – two phenomena that can lead to substantial reductions in EQE. However, it should be taken into account that a wide-gap host matrix can reduce power efficiency, resulting from a considerable increase in driving voltage. A three-component EML also increases the complexity and cost of device fabrication. In the recent study, near 100% internal quantum efficiency was demonstrated from a two-component matrix-free hyperfluorescence with deep and pure blue emission for the first time by combining efficient nondoped TADF materials and ultranarrow deep blue emitters. 

Related publications

1. Suppression of Dexter transfer by covalent encapsulation for efficient matrix-free narrowband deep blue hyperfluorescent OLEDs 

      Nature Materials, 23, 519–526 (2024)

2. TADF host engineering for improved pure blue matrix-free hyperfluorescent OLEDs with ultranarrow emission

      Advanced Optical Materials, 13, 2500246 (2025)

Research 02

Doublet fluorescence

Despite extensive research on near-infrared organic light-emitting diodes, the external quantum efficiency (EQE) of these devices is far lower than devices with visible light emission: typically under 5% EQE for 800 nm and longer wavelengths. Recently, doublet fluorescent emission from organic radicals has emerged as a new route to more efficient light-emitting devices than those using established non-radical organic emitters. Charge recombination in radical devices results in doublet excitons with nanosecond emission and avoids the efficiency limit usually associated with singlets and triplets. Luminescent organic radicals can have high photoluminescence quantum yield (PLQY) in the near-infrared (NIR) range, where immunity from normal ‘energy gap law’ considerations is enabled by suppressing the nonradiative losses through decoupling high-frequency vibrational modes. The recent research results shows high-performing doublet fluorescent NIR OLEDs exploiting charge control and energy transfer design of nonradical host:radical guest systems. 

Related publications

1. Efficient and Bright Organic Radical Light-Emitting Diodes with Low Efficiency Roll-Off 

       Advanced Materials, 35, 2303666 (2023)

2. Efficient near-infrared organic light-emitting diodes with emission from spin doublet excitons  

       Nature Photonics, 18, 905-912 (2024)

3. Near-infrared Light-Emitting Diodes from Organic Radicals with Charge Control 

       Advanced Optical Materials, 10, 2200628 (2022)

Research 03

Emerging classes of organic semiconductors: Chiral materials and coinage metal complexes

We explore cutting-edge organic semiconductors beyond conventional materials, including coinage metal complexes and chiral semiconductors for circularly polarized devices. These emerging material classes offer unique electronic and optical properties that enable novel device functionalities and overcome limitations of traditional organic emitters. Through systematic investigation of their structure-property relationships and device implementation, we advance the frontier of organic optoelectronic technologies.

Related publications

1. Circularly polarized electroluminescence from chiral supramolecular semiconductor thin films 

     Science, 387, 1175-1181 (2025)

2.  Deep-blue and Fast Delayed Fluorescence from Carbene-Metal-Amides for Highly Efficient and Stable Organic Light-Emitting Diodes

     Advanced Materials, 36, 2404357 (2024)

3.  Matrix-free Hyperfluorescent Organic Light-Emitting Diodes Based on Carbene-Metal-Amides

     Advanced Optical Materials, 9, 2001965 (2021)

Research 04

Others: Device engineering, exciton dynamics, and dipole orientation

We develop diverse OLED architectures including white OLEDs for lighting, tandem structures for enhanced efficiency and voltage control, optical cavity designs for narrowband emission, patterning substrates for enhancing light extraction, and inverted configurations for improved stability. Our research encompasses both vacuum-deposited and solution-processed fabrication methods, addressing orthogonality challenges and layer compatibility for scalable manufacturing. Through systematic optimization of device stacks and processing conditions, we enable high-performance OLEDs suitable for various display and lighting applications. 

Sophisticated light-matter interactions, such as triplet-triplet annihilation photon upconversion, singlet fission for enhanced charge generation, and dipole orientation control for optimized light outcoupling, offer pathways to breakthroughs in optoelectronic technologies. These processes enable substantial improvements in device performance by harvesting otherwise lost energy or maximizing photon extraction. Through systematic spectroscopic analysis and material engineering, we develop strategies to manipulate excited-state dynamics and molecular orientation for next-generation high-performance optoelectronic applications.