To understand why Adachi’s work has attracted such sustained attention, it helps to consider the basic physics of organic light-emitting diodes. In an OLED, electricity drives electrons and holes into a thin film of organic molecules, where they combine to form excitons, bound pairs of a negatively charged electron and a positively charged hole. Quantum mechanics dictates that these excitons form in two spin states: singlets, which are bright and can emit light directly, and triplets, which are dark in conventional fluorescent molecules. Statistical rules mean that roughly three-quarters of the excitons generated electrically are triplets, which means first-generation OLEDs built from ordinary fluorescent emitters could theoretically harvest only about 25 percent of the excitons created inside the device. That ceiling imposed a hard limit on efficiency, and for years it seemed that the only way around it was to borrow chemistry from the heavy end of the periodic table.

The second generation of OLED emitters did exactly that. By incorporating heavy metals such as iridium and platinum into phosphorescent molecules, researchers found a way to exploit strong spin-orbit coupling, an effect that mixes singlet and triplet character and allows the dark triplet excitons to emit light. Phosphorescent organic light-emitting diodes, known as PHOLEDs, pushed exciton utilization toward nearly 100 percent and delivered the dazzling efficiencies that made OLED televisions and smartphone displays commercially viable. Yet the approach carried real costs. Heavy metals like iridium are rare, expensive, and subject to supply constraints, and phosphorescent emitters have struggled with limited operational stability, a problem that has been particularly stubborn for blue-emitting materials, which are essential for full-color displays. The industry needed a route to the same near-total exciton harvesting without dependence on scarce elements.

Adachi’s answer was to find a purely organic way to recycle triplet excitons, and the mechanism he established is now widely regarded as the third generation of OLED emission technology. TADF exploits a subtle quantum-mechanical property of certain organic molecules: when the energy gap between the lowest singlet and triplet states is small enough, thermal energy at room temperature is sufficient to drive triplet excitons back up into the emissive singlet state, a process called reverse intersystem crossing. Once converted, these delayed singlet excitons fluoresce just like the directly formed ones, so the molecule effectively harvests both spin populations and can in principle approach 100 percent internal efficiency using nothing but lightweight, abundant organic compounds. The trick depends on careful molecular engineering, typically involving donor and acceptor units twisted apart so that the highest occupied and lowest unoccupied molecular orbitals overlap only minimally, which shrinks the singlet-triplet splitting while preserving enough charge-transfer character to allow light emission.

The landmark demonstration came in a 2012 Nature paper by Hiroki Uoyama, Kenichi Goushi, Katsuyuki Shizu, Hiroko Nomura, and Chihaya Adachi, titled Highly efficient organic light-emitting diodes from delayed fluorescence. That publication laid out the molecular design principles underlying TADF emitters and showed experimentally that purely organic molecules could rival the efficiency of their heavy-metal counterparts. The paper became one of the most cited works in the field, and its influence is precisely what the Citation Laureate designation measures. In the years since, TADF has grown from a single elegant proof of concept into a major global research area, with hundreds of laboratories pursuing new emitter architectures, faster reverse intersystem crossing, and improved color purity and device lifetimes. The field’s expansion has accelerated progress in both fundamental photophysics and commercial OLED development, as manufacturers seek emitters that combine high efficiency, long operational stability, and freedom from rare-metal supply chains.

What makes the TADF story scientifically compelling is that it emerged from reframing a limitation as an opportunity. As Adachi explained upon receiving the honor, the breakthrough came from a shift in perspective: finding ways to harness charge-transfer interactions that were once thought to limit light emission and were considered detrimental, and turning them into a mechanism for creating new emissive functions in organic molecules. In many molecular systems, charge-transfer states are dim and inefficient, and designers traditionally worked to suppress them. Adachi’s group recognized that in the right molecular geometry, those same states could serve as a bridge that funnels triplet excitons into bright singlet emission. That conceptual inversion, treating a supposed defect as the engine of the device, is the kind of insight that reshapes a discipline, and it is the core of what Clarivate’s evaluators identified as Nobel-class influence.

The recognition also places Adachi alongside the researchers who built the generation of technology his work superseded. Forrest and Thompson were honored for their pioneering contributions to phosphorescent OLEDs, the heavy-metal-based emitters that constituted the second generation of the technology. Their work demonstrated that triplet harvesting was possible at all and proved the commercial promise of ultra-efficient OLEDs, while Adachi’s TADF showed that the same goal could be achieved without rare metals. Viewed together, the three laureates trace the full arc of organic light-emitting science: from fluorescent devices that wasted three-quarters of their excitons, through phosphorescent devices that captured nearly all of them at the price of iridium and platinum, to metal-free devices that harvest triplets through thermal activation. That combined lineage has enabled the highly efficient and more sustainable display technologies in widespread use today.

The practical implications extend well beyond the screens in pockets and living rooms. Because TADF emitters can be engineered from abundant organic materials, they reduce reliance on critical raw materials whose mining and refining carry environmental and geopolitical burdens. Adachi’s research program has pushed the concept further through hyperfluorescence, an architecture in which a TADF molecule acts as a sensitizing donor that transfers its energy to a conventional fluorescent emitter, combining the triplet-harvesting ability of TADF with the narrow, color-pure emission of fluorescence. Such hybrid systems are considered promising candidates for next-generation displays that demand both high efficiency and precise color rendering. According to the announcement, the technology’s potential reaches into wearable devices, automotive displays, and medical and healthcare technologies, domains where flexible, lightweight, and efficient light sources are transforming product design.

Adachi said he was deeply honored to receive the Clarivate Citation Laureate Award, adding that the recognition reflects the contributions of the many researchers, students, and collaborators who helped advance the field. He noted that the honor motivates him to further develop TADF and hyperfluorescence technologies for next-generation OLEDs and to explore new organic materials that contribute to both fundamental science and future industries. That forward-looking stance is characteristic of a researcher whose laboratory at Kyushu University has remained at the center of organic photonics for decades, training generations of scientists and maintaining collaborations that span academia and industry.

For the broader scientific community, the 2026 Citation Laureate list, which named 22 researchers across Physiology or Medicine, Physics, Chemistry, and Economics, serves as a reminder that the most transformative technologies often rest on decades of patient work in photophysics and molecular design. Every OLED display now in use embodies the quantum spin statistics that once seemed an insurmountable efficiency barrier, and the successive generations of emitters that overcame it. Adachi’s TADF stands as the clearest demonstration that clever molecular engineering can substitute for scarce elements, a lesson whose importance is only likely to grow as display technology, lighting, and organic electronics continue to expand and as the world seeks high-performance materials that do not depend on limited natural resources.

Subject of Research: Thermally activated delayed fluorescence for high-efficiency metal-free organic light-emitting diodes

Article Title: Kyushu University Distinguished Professor Chihaya Adachi receives Clarivate Citation Laureate Award for pioneering next-generation organic electronics

Article References: Kyushu University Distinguished Professor Chihaya Adachi receives Clarivate Citation Laureate Award for pioneering next-generation organic electronics. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Chihaya Adachi, TADF, OLED, Clarivate Citation Laureate, Kyushu University, organic electronics, phosphorescent OLEDs, excitons, display technology, hyperfluorescence, rare metals, optoelectronics

To understand why this matters, it helps to consider what actually happens inside an OLED when a current flows. Electrons and holes recombine in an emissive layer, and in phosphorescent OLEDs those recombining excitations are triplet excitons harvested by organometallic emitter complexes, allowing nearly all electrically generated excitons to be converted into photons in principle. Internal quantum efficiencies approaching unity are therefore achievable. The trouble lies further downstream. In a planar, multilayer device, only a modest fraction of the light created in the emissive layer can escape directly into air. The remainder is trapped in three competing channels: photon modes guided laterally through the high-index organic and substrate layers, cavity modes in top-emitting structures, and surface plasmon polaritons, which are coupled oscillations of electromagnetic fields and conduction electrons that propagate along metal-organic interfaces. Each trapped channel represents energy that has already been generated but will never reach the viewer’s eye.

Surface plasmon polaritons are particularly punishing in modern device geometries. Inverted OLED architectures, in which the cathode sits beneath the emissive stack and the anode is deposited on top, are attractive for display manufacturing because they allow robust electrical interconnection, oxide-based thin-film transistors and seamless tiling. Yet the metallic electrodes and thin functional layers characteristic of these designs place the emissive layer within the evanescent near field of metal surfaces, exactly the regime in which coupling to surface plasmon polaritons is strongest. The energy funneled into these modes is dissipated as heat within tens of femtoseconds to picoseconds, contributing nothing to brightness while accelerating the degradation of organic molecules around it. Efficiency and operational stability are therefore fundamentally limited by these photonic losses, and researchers have spent two decades searching for ways to either suppress the coupling or recover the energy after it has been captured.

The new work introduces an unexpectedly versatile medium for doing precisely that: a colloidal quantum dot interlayer positioned within the inverted phosphorescent OLED stack. Quantum dots are nanoscale semiconductor crystals whose optical properties can be tuned simply by changing their size, and they have become workhorses of modern optoelectronics in displays and color-conversion films. Here, the team exploited a different facet of their behavior. Because the emission spectrum of the OLED’s phosphorescent emissive layer overlaps spectrally with the absorption and plasmonic response of the quantum dot layer, excitons in the organic emitter can couple efficiently to the dots through the near field. Rather than acting as a passive spacer, the interlayer functions as a plasmonic coupling medium that intercepts energy flowing into surface plasmon polariton modes before it is irreversibly lost, and makes that energy available for re-emission and extraction.

The experimental evidence for this coupling came from time-resolved photoluminescence measurements, a technique that tracks how quickly excitons in the emissive layer decay after excitation. When excited emitters are placed near a metal surface, coupling to plasmon modes typically accelerates their decay, shortening the measured lifetime while converting much of the energy into heat. By comparing the photoluminescence dynamics of devices in which the quantum dot interlayer was present against configurations with conventional spacer layers, the researchers revealed an efficient plasmonic coupling between the emissive layer and the dots. The modified decay dynamics showed that energy which would otherwise have been dissipated through surface plasmon polaritons was instead being transferred into the quantum dot layer, where it could be recycled into radiative channels. This spectroscopic fingerprint established the physical mechanism before device-level gains were even measured.

Complementing the experiments, the team performed three-dimensional finite-difference time-domain simulations, a computational method that solves Maxwell’s equations on a fine spatial grid and captures how electromagnetic energy flows through complex multilayer structures. The simulations demonstrated that the quantum dot interlayer modifies the local density of optical states, the fundamental quantity that determines how readily an emitter can shed energy into each available optical channel. By reshaping this density of states, the interlayer redistributes trapped optical energy among the device’s modes and enhances outcoupling into air modes, the channels that carry light to the outside world. The modeling quantified where the energy went, confirming that a substantial portion of the plasmonic fraction was being diverted away from lossy surface waves and toward extractable radiation, in quantitative agreement with the device measurements.

The quantitative accounting is striking. According to the analysis, the quantum dot interlayer intercepts approximately 30.7 percent of the energy that would initially have been coupled into surface plasmon polariton modes in the reference device. Recovering nearly a third of this previously doomed energy translated directly into the headline performance figures. The quantum dot-integrated inverted phosphorescent OLED achieved an external quantum efficiency of 20.95 percent, compared with 15.67 percent for the reference device without the interlayer, an improvement factor of 1.3. For an intervention that adds a single solution-processed nanomaterial layer to an existing architecture, and which touches neither the emitter chemistry nor the electrode design, this is a remarkably efficient lever on device performance, and one that should be directly relevant to the display industry, where fractions of a percent in efficiency carry substantial value.

The strategy also stands out against earlier attempts to tame plasmonic losses. Previous approaches have included nanostructured electrodes, microcavity engineering, metal nanoparticles doped into transport layers, plasmonic quasi-bandgap designs and polariton-enhanced Purcell effects. Each has shown promise, but many demand complicated fabrication, introduce new sources of optical absorption or electrical instability, or trade off angular color uniformity for efficiency. Embedding gold or silver nanoparticles, for instance, can enhance emission through localized plasmon resonance but risks quenching excitons and degrading device lifetime. The quantum dot interlayer approach avoids directly doping the charge transport layers and instead exploits a well-controlled, spectrally matched coupling medium, giving designers a knob they can tune through dot size, composition and placement. Because colloidal quantum dots are already manufactured at scale for display applications, the pathway from laboratory demonstration to production integration is unusually short.

The research was carried out by Thi Thuy Truong, Hai Truyen Dang, Nisha Vergineya S and Jang Hyuk Kwon at Kyung Hee University’s Department of Information Display in Seoul, together with Malte C. Gather of the Humboldt Centre for Nano- and Biophotonics at the University of Cologne and the University of St Andrews. It was supported by the Korean Ministry of Trade, Industry and Energy through programs on core AMOLED microdisplay technologies for extended-reality devices and industrial innovation foundations, and by the European Research Council through an Advanced Grant under the Horizon Europe Framework Programme. Beyond the immediate efficiency gains, the findings establish quantum dot interlayers as an effective and versatile platform for suppressing plasmonic losses in high-performance OLEDs, with implications for brighter, longer-lived and more energy-efficient displays, lighting and microdisplays. If roughly a third of plasmonic energy can be intercepted with one inserted layer, the remaining plasmonic losses in OLED technology now look less like a fundamental ceiling and more like a recoverable resource waiting to be harvested.

Subject of Research: Use of colloidal quantum dot interlayers to recover surface plasmon polariton losses and enhance efficiency in inverted phosphorescent OLEDs

Article Title: Inverted phosphorescent OLEDs with plasmon coupling from quantum dot interlayers for enhanced efficiency

Article References: Inverted phosphorescent OLEDs with plasmon coupling from quantum dot interlayers for enhanced efficiency. (n.d.). https://doi.org/10.1038/s41566-026-02001-2

Image Credits: AI Generated

DOI: 10.1038/s41566-026-02001-2

Keywords: OLED, phosphorescent OLEDs, quantum dots, surface plasmon polaritons, light extraction, external quantum efficiency, plasmon coupling, local density of optical states, inverted device architecture, nanophotonics, finite-difference time-domain simulation, display technology