Advanced Optical Materials最新文献

Two-dimensional (2D) in-plane heterostructures including compositionally graded alloys and lateral heterostructures with defined interfaces display rich optoelectronic properties and offer versatile platforms to explore one-dimensional (1D) interface physics and many-body interaction effects. Graded Mo_xW_{1 − x}S₂ alloys show smooth spatial variations in composition and strain that continuously tune excitonic emission, while MoS₂–WS₂ lateral heterostructures contain atomically sharp interfaces supporting 1D excitonic phenomena. These single-layer systems combine tunable optical and electronic properties with potential for stable, high-performance optoelectronic devices. Hyperspectral and nano-resolved photoluminescence (PL) imaging enable spatial mapping of optical features along with local variations in composition, strain, and defects, but manual interpretation of such large datasets is slow and subjective. Here, a fast and scalable unsupervised machine-learning (ML) framework is introduced to extract quantitative and interpretable information from hyperspectral PL datasets of graded Mo_xW_{1 − x}S₂ alloys and MoS₂–WS₂ heterostructures. Combining principal-component analysis (PCA), t-distributed stochastic neighbor embedding (t-SNE), and density-based spatial clustering of applications with noise (DBSCAN), spectrally distinct domains associated with composition, strain, and defect variations are uncovered. Decomposition of representative spectra reveals multiple emission species, including band-edge excitons and defect-related transitions, demonstrating that ML-driven analysis provides a robust and automated route to interpret rich optical properties of 2D materials.

The selective threefold para-functionalization of the dimethylmethylene-bridged phosphorus-centered heterotriangulene is achieved via an iridium-catalyzed borylation. Conversion of the borylated compound to the corresponding bromo derivative, followed by a Buchwald–Hartwig cross-coupling with aromatic amines, affords a series of donor-acceptor fluorophores in which the central phosphoryl moiety acts as a moderate electron acceptor. The compounds exhibit an intense blue photoluminescence, which is characterized by comprehensive spectroscopic studies both in solution and in thin films, supported by density functional theory calculations, as thermally activated delayed fluorescence (TADF). Especially, the carbazole-substituted compounds show considerably narrower emission bands compared to previously reported triphenylphosphine oxide-derived systems. These findings highlight the beneficial effect of the phosphorus-centered heterotriangulene on the photophysical characteristics due to its increased rigidity imparted by the C(sp³)-based bridging moieties.

Organic photodiodes (OPDs) are considered a next-generation technology for light sensors. However, concerns have arisen regarding the reliable reporting of device performance, particularly under low illumination conditions. The potential factors range from instrumental limitations to questionable assumptions. This work addresses these concerns. The standardized metrics for photodetection are revisited to draw inferences for implementing an appropriate measurement setup and methodical approach for reporting the following steady-state metrics: dark noise, dark current, photocurrent, specific detectivity, responsivity, and (linear) dynamic range. The setup involves a highly sensitive electrometer capable of recording down to femtoampere currents, calibrated optical filters to accurately tune the incident optical power over 12 decades, illumination sources with narrowband emission spectra, baffle plates for stray light mitigation, and a light-tight metallic box to shield the setup from ambient electromagnetic fields. Thorough information on each component, its calibration details, and open-source Python scripts to run the experiments are provided. Subsequently, an OPD and a reference silicon photodiode are characterized, and the accuracy and reliability of the setup are validated. Essentially, this work provides a robust framework to accurately measure and reliably report the standardized photodetecting metrics of next-generation photodiodes.

Singlet fission (SF) is a process in which a singlet exciton is converted into two triplet excitons, significantly enhancing charge generation in organic solar cells. It has been shown that the rate of SF and the lifetime of the generated triplet excitons strongly depend on the molecular arrangement. In this work, a cofacial orientation of pentacene molecules is achieved by embedding organic linkers containing pentacene in a surface-anchored metal–organic framework. Transient absorption spectroscopy and a quantum mechanical analysis are used to analyze the exciton dynamics in a broad spectral range from near-ultraviolet to near-infrared. The observed spectra indicate that a singlet excited state generates a correlated triplet pair within a few picoseconds. Subsequent dynamics show the formation of long-lived excitons ($��39��\mu �s�$) with triplet character. This exceeds by far the observed lifetime of triplet excitons generated in pentacene thin films and may enhance triplet exciton harvesting capabilities in photovoltaic cells.

Hybrid manganese metal halides have emerged as promising candidates for next-generation X-ray scintillators due to their intense radioluminescence and environmental friendliness. However, challenges in cation engineering and scalable fabrication hinder the development of high-resolution, large-area, and flexible scintillator screens. Herein, a novel zero-dimensional organic-inorganic manganese (II) halide, denoted as (C₂₅H₃₀P)₂MnBr₄, is designed featuring sterically bulky triphenylphosphonium cations that synergistically enhance the photoluminescence quantum yield (PLQY = 99.2%) and radioluminescence efficiency. The (C₂₅H₃₀P)₂MnBr₄ single crystal exhibits outstanding scintillation properties, exhibiting a record-high light yield of 85 000 photons MeV⁻¹, an excellent linear response to X-ray dose rate (5.52 µGy_air s⁻¹ to 1.13 mGy_air s⁻¹), and an ultra-low detection limit of 25 nGy_air s⁻¹. Furthermore, a flexible free-standing (C₂₅H₃₀P)₂MnBr₄-thermoplastic polyurethane (TPU) composite film is demonstrated, fabricated via a room-temperature in situ strategy. This film achieves an ultra-large active area (>9000 mm²), uniform transparency, and exceptional mechanical flexibility. The (C₂₅H₃₀P)₂MnBr₄-TPU yielded a high spatial resolution of 13.4 lp mm⁻¹ while achieving high-quality imaging of complex 3D objects under low-dose X-ray irradiation. This work establishes a generalizable framework for designing large-area and high-resolution scintillators through cation engineering and polymer matrix integration, opening new avenues for next-generation flexible X-ray imaging technologies.

A promising material for optical applications is transparent polycrystalline alumina (Al₂O₃) ceramics, owing to their excellent mechanical properties and thermal and chemical stability. However, the light transmittance of Al₂O₃ polycrystalline ceramics is mainly limited by grain scattering (birefringence) and pore scattering, resulting in a lower transmittance than single-crystal sapphire. An effective approach to minimize grain scattering and pore scattering is to refine grains and reduce porosity and pore sizes. To achieve near-theoretical transparency in Al₂O₃ ceramics, in our present work, the grains in Al₂O₃ polycrystalline ceramics are refined to 13 nm, from our homemade nanoparticles and by high-pressure/low-temperature sintering. Typically, the synthesized Al₂O₃ nanocrystalline ceramic exhibits 82% in-line transmittance at 0.8 mm thickness and a wavelength of 640 nm, which is not only superior to the reported doped, undoped, and textured Al₂O₃ ceramics (78%) but even close to that of single-crystal sapphire (86%). The reasons behind this are analyzed and discussed. Our results confirm that refinement of nanograins is an effective approach to enhance the transparency of anisotropic polycrystalline ceramics.

β-Ga₂O₃ is a promising ultra-wide bandgap semiconductor with substantial potential for optoelectronic applications. A deeper understanding of its carrier dynamics is essential for optimizing device performance. In this study, the carrier dynamics in unintentionally doped β-Ga₂O₃ (100) single crystals across a broad range of timescales, from sub-picosecond to microseconds, are investigated. The sub-picosecond dynamics are resolved into three distinct kinetic components: two Gaussian processes, which are attributed to nondegenerate two-photon absorption, and a single-exponential decay corresponding to hot carrier relaxation. Additionally, defect-state-mediated carrier recombination processes that occur on timescales ranging from picoseconds to microseconds are explored. These findings offer valuable insights into the photophysical properties of β-Ga₂O₃, providing a foundation for optimizing its performance in future optoelectronic devices.

A series of high-performance NIR phosphors Mg₄Al_4.5Ga_2.45B_1.05O₁₆: xCr³⁺ (MAGBO: xCr³⁺) with high internal quantum efficiency (IQE, 95.7%), excellent thermal stability (87.5% at 373 K and 73% at 423 K), and various, especially large FWHM (250 nm) are designed for wireless communication as excited by near-ultraviolet LEDs. The emission is adjusted from 600–950 to 670–1370 nm with a peak at 703–878 nm and a narrow band (FWHM = 49 nm) to an ultra-broadband (FWHM = 250 nm) as the Cr³⁺ ions increase. The variations in FWHM and emissions at low temperatures verify three emission centers. Notably, the energy transfer from the high-energy Cr³⁺ center to the low-energy Cr³⁺ ions in MAGBO is systematically investigated using the temperature-dependent emission and the decay curves. An NIR pc-LED device combined with the MAGBO:0.15Cr³⁺ phosphor with a 395 nm chip demonstrates stable NIR emission under different driving currents. The photoelectric conversion efficiency is 15.8% at 20 mA, and an output power of 120 mW is achieved at 500 mA. The fabricated pc-LED device is successfully applied for rapid imaging of hand and fist veins, night vision of objects, and encrypted information reading, especially in wireless communication.

The development of multimodal dosimeters capable of preserving independent luminescent signals is a transformative goal in radiation sensing. Here, Eu-doped LiCaAlF₆ nanoparticles (NPs) are synthesized via a hydrothermal route. The synthesis parameters are systematically optimized. XRD confirmed single-phase formation at low Eu concentrations. Spectroscopic analyses (XPS, PL, and time-resolved emission) verified the predominance of Eu²⁺ ions, responsible for the intense blue emission under X-ray excitation. Dosimetric performance is assessed by radioluminescence (RL), thermoluminescence (TL), and optically stimulated luminescence (OSL). RL results revealed a relationship between Eu-doping concentration and x-ray fluence, suggesting that samples with higher %Eu are better suited for applications involving elevated photon fluence, such as flash radiotherapy. Samples with the smallest crystallite size exhibited the highest TL and OSL intensity and sensitivity. NPs doped with 0.1 mol% Eu and synthesized with PVP exhibited superior sensitivity and linear dose-response, achieving minimum detectable doses of 4.7 mGy (TL) and 8 mGy (OSL). These samples demonstrated unprecedented behavior, maintaining intense TL signals even after complete OSL readout, thereby revealing uncorrelated TL and OSL processes within the same material system. This unique characteristic allows sequential and non-destructive dose assessments, enabling the development of versatile, multimodal radiation detection platforms.

Near-infrared (NIR) meta-optics often suffer from a limited field of view (FOV) and bandwidth in compact designs. While metasurfaces offer high design freedom in the lateral dimension, computational methods provide more flexibility for achieving precise control over the thickness dimension, offering a superior approach to reach the physical limits of the system. Here, a computational imaging method based on physics-constrained embedded training, which integrates intrinsic physical constraints, including chromatic dispersion and fabrication tolerances, into the forward imaging simulation and neural network training, is proposed. This approach is demonstrated through the implementation of a NIR camera featuring a 6.8-mm-diameter monochromatic metalens, which, when coupled with a nonlinear activation-free generative adversarial network, achieves broadband achromatic imaging with a FOV of 78° across the 800–1000 nm spectral range. The camera successfully captures real-world scenes with high fidelity, enabling applications like vein detection.