Traditionally, organic luminescent materials have been classified based on their ability to exhibit either fluorescence or phosphorescence, two fundamentally different types of light emission originating from distinct excited-state processes. Fluorescence involves the prompt emission of photons as excited electrons return to the ground state, typically within nanoseconds. In contrast, phosphorescence arises from the slower relaxation of electrons trapped in a triplet excited state, extending emission lifetimes into microseconds and beyond. The ability to simultaneously manipulate both these emissive pathways within a single material platform has long challenged scientists due to the conflicting time scales and spin multiplicities involved.

The research team addressed this challenge by designing an organic luminescent system that strategically incorporates multiple excited states, thereby enabling efficient intersystem crossing and reverse intersystem crossing mechanisms in tandem. By fine-tuning the molecular architecture, they successfully achieved a material where delayed fluorescence—a form of thermally activated delayed fluorescence (TADF)—and phosphorescence coexist. This dual emission process was demonstrated under ambient conditions, a critical criterion for practical applications.

Central to this revelation is the molecular engineering that balances singlet and triplet excited states, allowing the material to harness triplet excitons that traditionally remain non-radiative or contribute to phosphorescence only. In this system, the conversion of triplet excitons back to singlet states facilitates delayed fluorescence. Concurrently, a portion of the triplet population emits directly through phosphorescence. The concurrency of these radiative decay channels is meticulously controlled through quantum yield optimization and excited state energy alignment.

The implications of this discovery extend beyond fundamental photophysics to real-world applications. Organic light-emitting diodes (OLEDs), a technology increasingly pervasive in modern display and lighting systems, stand to benefit significantly. By leveraging both delayed fluorescence and phosphorescence, devices can attain higher internal quantum efficiencies without relying on heavy metal dopants, which are not only costly but pose environmental concerns. This all-organic approach promises more sustainable and efficient OLED designs.

Moreover, the ability to tune the emission via multiple excited states opens new possibilities for color purity and tunability in lighting applications. Traditional phosphorescent materials often suffer from spectral broadening or color instability, while pure fluorescence emitters may lack efficiency. The dual mechanism stabilizes emission profiles and enhances brightness, potentially enabling customizable, high-resolution displays and adaptive lighting systems responsive to environmental inputs.

In the realm of bioimaging, organic compounds exhibiting prolonged emission lifetimes, namely through delayed fluorescence and phosphorescence, can significantly improve imaging resolution and contrast by minimizing background fluorescence. This allows for time-gated imaging techniques that isolate the desired luminescent signals, an advantage this new material system could amplify, offering more sensitive diagnostic tools and real-time bio-probes.

The authors employed an array of spectroscopic techniques to unravel the material’s excited-state dynamics, including time-resolved photoluminescence and transient absorption measurements, validating the coexistence of delayed fluorescence and phosphorescence with distinct temporal profiles. Their rigorous characterization ensures that the observed dual emission is intrinsic to the molecular design rather than an artifact of environmental variations or impurities.

Additionally, computational studies using quantum chemical calculations provided insight into the energy landscape and spin-orbit coupling effects governing intersystem crossing rates. The simulations guided the rational design of molecular entities with appropriate singlet-triplet energy gaps, a critical parameter for efficient reverse intersystem crossing that underpins delayed fluorescence.

This research represents a paradigm shift in the understanding and utilization of organic luminescent materials. By demonstrating control over multiple excited states to enable concurrent delayed fluorescence and phosphorescence, it redefines the boundaries of organic optoelectronics. The ability to engineer materials with tailored emission kinetics and spectral properties unlocks synergies previously deemed incompatible within a single molecular platform.

Future directions proposed by the team include expanding the molecular library of such dual-emissive compounds and integrating these materials into functional devices to test performance under operational conditions. They highlight the promise of this approach not only in OLEDs but also in organic lasers, sensing devices, and luminescent solar concentrators, suggesting a broad technological impact.

Challenges remain, particularly in scaling synthesis, ensuring long-term stability, and optimizing emission efficiency across the visible spectrum. However, the foundational knowledge established in this study offers a research roadmap toward overcoming these hurdles. Collaborative efforts bridging chemistry, physics, and engineering will be pivotal in translating this molecular innovation into commercial products.

In essence, Dou and colleagues’ breakthrough underscores the power of rational molecular design combined with mechanistic insight to circumvent limitations inherent in organic luminescent materials. This work exemplifies how a nuanced understanding of excited-state multiplicities and their interplay can be leveraged to craft materials with unprecedented photophysical properties, influencing a spectrum of scientific and industrial fields.

As the demand for sustainable, efficient, and versatile lighting and display technologies intensifies, such advances underscore the critical role of fundamental science in driving innovation. The confluence of delayed fluorescence and phosphorescence within a singular organic emitter charts a new course for the next generation of luminescent materials, heralding a future where organic electronics can achieve previously unattainable levels of performance and functionality.

Subject of Research:
Organic luminescent materials exhibiting simultaneous delayed fluorescence and phosphorescence through multiple excited states.

Article Title:
Simultaneous delayed fluorescence and phosphorescence in organic luminescent material employing multiple excited states.

Article References:
Dou, D., Liu, W., Zhou, X. et al. Simultaneous delayed fluorescence and phosphorescence in organic luminescent material employing multiple excited states. Light Sci Appl 15, 4 (2026). https://doi.org/10.1038/s41377-025-02063-x

Image Credits:
AI Generated

DOI:
01 January 2026

Brain organoids, miniature and simplified versions of the brain cultivated in vitro from stem cells, have rapidly become indispensable tools for biomedical research. Yet, their densely packed and complex cellular architecture demands imaging systems capable of revealing ultrastructural details far beyond the limits imposed by traditional optical microscopy. Conventional methods often fall short in resolving fine details within these organoids, limiting observations to relatively lower resolution planes and thereby constraining the biological insights that researchers can gain.

The research team, composed of Yi Jo, Hyun Park, Seo Lee, and colleagues, has innovatively integrated the concept of image scanning microscopy (ISM) with the emerging technology of metalenses—ultrathin, nanostructured lenses engineered to precisely control light propagation at the subwavelength scale. Unlike conventional glass lenses, metalenses can be designed with multiple focal points, allowing simultaneous scanning of several depths within a sample, drastically enhancing imaging throughput while maintaining exceptional resolution.

Central to this achievement is the fabrication of a multifocal metalens capable of generating a pattern of focused light spots across the sample. By coupling this with a highly sensitive detector and sophisticated scanning algorithms, the system reconstructs images with spatial resolutions surpassing the classical diffraction limit—a feat that unlocks visualization of previously inaccessible subcellular features within brain organoids.

The implications of this work extend beyond mere technical curiosity. High-resolution, volumetric imaging of brain organoids can accelerate the understanding of neural circuitry formation, synaptic connectivity, and pathological alterations associated with diseases such as Alzheimer’s, epilepsy, and autism spectrum disorders. Enhanced imaging clarity also facilitates drug screening and therapeutic interventions by enabling precise monitoring of cellular responses in three dimensions.

Technically, the multifocal metalens in this system is engineered using nanophotonic principles, where arrays of microscopic pillars or nanoantennas are etched onto a substrate to manipulate phase, amplitude, and polarization of incident light. This precise nanofabrication allows tailoring of the metalens’ optical response to create multiple tightly focused spots of light distributed laterally and axially, enabling parallel scanning.

Image scanning microscopy traditionally involves scanning a focused laser beam across a fluorescent sample and detecting emitted light to construct an image. Through the multifocal metalens, multiple excitation points are scanned concurrently, significantly reducing imaging time while improving signal-to-noise ratios, thanks to the reduced excitation power per focal point avoiding photodamage to sensitive biological samples.

Moreover, this optical configuration seamlessly integrates into existing microscopy platforms due to the planar and compact nature of the metalenses, eliminating bulk optics and enabling the miniaturization of super-resolution microscopes. This accessibility opens doors for widespread adoption in various laboratories, promoting advances in biomedical research worldwide.

The optimization process described involves fine-tuning the metalens design to balance focal spot size, depth of field, and intensity uniformity across multiple focus points. This ensures that all regions of the brain organoid are illuminated and imaged with consistent resolution and contrast, crucial for the quantitative analysis of intricate biological features.

Furthermore, the authors demonstrate the successful application of their system by imaging brain organoids stained with fluorescent markers highlighting distinct cellular compartments, revealing unprecedented levels of detail within their complex microenvironment. The sub-diffraction-limit imaging capability enabled visualization of dendritic spines and fine neuronal processes, structures essential for understanding neural communication pathways.

The integration of computational post-processing algorithms further enhances image reconstruction, compensating for aberrations and extracting meaningful data from raw fluorescence signals. This synergy of hardware innovation and software sophistication is a hallmark of modern super-resolution microscopy developments.

In addition to its biological applications, the technology holds promise for diverse fields requiring nondestructive, high-resolution optical imaging, including materials science, nanotechnology, and live-cell imaging, potentially revolutionizing microscopic examination protocols across disciplines.

Challenges remain, including scaling the production of such intricate metalenses and integrating them into commercial instruments, but the demonstrated proof-of-concept underscores a robust framework upon which future innovations can expand. Collaborative efforts between physicists, engineers, and biologists are anticipated to push this technology toward clinical translations, particularly for diagnostics and therapeutic monitoring at the micro and nanoscale.

Ultimately, the work of Jo and colleagues illuminates a path toward overcoming longstanding barriers in optical resolution, offering a powerful, versatile, and efficient imaging tool that promises to deepen our understanding of brain development, function, and disease with unprecedented fidelity. As brain organoid research continues to evolve, this multifocal metalens-based ISM methodology will likely become an indispensable asset in the neuroscientist’s toolkit.

Subject of Research: Optical imaging advancements for sub-diffraction-limited visualization of brain organoids using multifocal metalens-based image scanning microscopy.

Article Title: Image scanning microscopy based on multifocal metalens for sub-diffraction-limited imaging of brain organoids.

Article References:
Jo, Y., Park, H., Lee, S. et al. Image scanning microscopy based on multifocal metalens for sub-diffraction-limited imaging of brain organoids. Light Sci Appl 14, 367 (2025). https://doi.org/10.1038/s41377-025-01900-3

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41377-025-01900-3