Advanced Optical Materials最新文献

Organic terahertz (THz) crystals with large optical nonlinearity and low phonon absorption are highly desirable for diverse THz applications. In this work, a novel molecular design strategy is introduced for developing high-performance organic THz salt crystals by introducing highly polar chlorinated substituent into the electron donor (ED) units of nonlinear optical cationic chromophores, a modification typically avoided due to concerns over reduced microscopic optical nonlinearity, for the first time. Compared to crystals based on non-chlorinated EDs, the newly designed chlorinated ED-based crystals exhibit significantly improved structural properties including reduced void volume, higher crystal density, and enhanced multiple-interionic interactions induced by chlorine substituents. These features lead to remarkably narrow and weak phonon absorption across the 0.5–2.2 THz range. Importantly, these crystals exhibit large microscopic and macroscopic optical nonlinearities, comparable to or exceeding those of non-chlorinated analogs. As a result, they deliver outstanding THz wave generation performance with a 0.32 mm thick 3Cl-OHQ-T crystal achieving a peak-to-peak THz electric field approximately 16 times higher than that of a 1.0 mm thick ZnTe crystal under identical excitation condition with 130 fs pump pulses at 1140 nm. Furthermore, the THz generators based on chlorinated ED-based crystals enable successful racemic detection of representative compounds.

Hyperbolic metamaterials, strategically engineered subwavelength structures, exhibit highly anisotropic electromagnetic properties that give rise to hyperbolic dispersion relations. This unique characteristic enables the support and manipulation of high-spatial-frequency modes that are inaccessible in conventional materials. In this review, the underlying principles and design strategies are presented for realizing hyperbolic metamaterials. An overview of their operation mechanisms, fabrication methods, and representative applications is provided. Furthermore, this review highlights how these structures enable unprecedented functionalities such as super-resolution imaging, scattering and absorption mode engineering, ultrasensitive sensing, and broadband absorption, which are rarely achievable with natural materials. In addition, they open pathways to further advancements, including all-optical switching, nonlinear optics, and magneto-optical sensing, thereby emphasizing their potential for next-generation photonics technologies.

The gadolinium garnet Gd₃Al₂Ga₃O₁₂ co-doped with Ce³⁺ and Cr³⁺ (GAGG-Ce,Cr) has been widely studied due to its unusual bright yellow long-lasting persistent luminescence properties. Here, rapid containerless melt-quenching is used as part of a two-step glass-crystallisation synthesis process to obtain a new highly nonstoichiometric form of this garnet, of composition Gd_3+x[Al₂Ga₃]_1-x/5O₁₂ with 0 ≤ x ≤ 0.6 (ns-GAGG). For compositions x > 0, powder X-ray diffraction analysis confirms that excess Gd³⁺ is accommodated at the Al³⁺/Ga³⁺ sublattice in octahedral coordination, by substituting up to 30% of these sites. This mode of substitution complexifies the local structure of the garnet host, which is shown to influence certain luminescence properties in the analogous highly nonstoichiometric Y_3+xAl_5-xO₁₂ (0 < x < 0.4) and Gd_3+xAl_5-xO₁₂ (0 < x < 0.6) systems. Co-doping ns-GAGG with Ce³⁺ and Cr³⁺ produces green-yellow persistent luminescence when x = 0, which undergoes a redshift to yellow-orange as the Gd³⁺ content increases to x = 0.4. However, this radical modification of the host composition does not strongly affect the afterglow kinetics. These results demonstrate an effective and high-precision way of decoupling color and kinetics in persistent luminescent garnets, which is usually hard to achieve using the standard stoichiometric material engineering approach.

Host-guest doped systems have demonstrated significant application prospects in organic luminescent materials, especially in application areas such as multicolor display technology, information encryption, and bioimaging. However, achieving both multi-stimuli response and full-color luminescence within a single host-guest system remains a significant challenge. Herein, the rational design and successful synthesis of a donor-acceptor (D-A) molecule, TOT-B, are reported. Significantly, when benchmarked against the donor molecule TOT, TOT-B demonstrates remarkable ratiometric multi-stimuli responsiveness toward light, fluoride ions, and pH changes in solution. Meanwhile, an isomorphic doping strategy is employed by blending TOT and TOT-B at different molar ratios, successfully constructing a full-color tunable photoluminescent crystal (blue to orange-red). Among them, the T-Y crystal exhibits rare multimodal emission properties, including mechanochromism (MC), mechanoluminescence (ML), and room-temperature phosphorescence (RTP). In addition, the combination of the TOT-B guest with various host molecules, such as cholic acid (CLA), benzophenone (BP), boric acid (BA), and polyethylene terephthalate (PET), can all exhibit phosphorescence, demonstrating excellent host-guest RTP versatility. This study elucidates correlations between host-guest interactions and luminescent properties via molecular engineering, enabling full-color luminescence and multi-stimuli responsiveness within a single system. These materials show utility in information encryption, dynamic anti-counterfeiting, and intelligent displays.

Hyperfluorescence also known as thermally activated delayed fluorescence (TADF) sensitized fluorescence is an innovative approach to achieve high performance organic light emitting diodes (OLEDs). Lighting applications rely on parameters such as external quantum efficiency (EQE) and colour purity. In this context, hyperfluorescence OLEDs (HF-OLEDs) are the leading technology due to its capability to combine the benefits of fluorescent dopants and TADF emitters to obtain saturated colour and long-term operational stability. Hyperfluorescence enabled through Förster resonance energy transfer (FRET) process which takes place between sensitizer and fluorescent emitter. Obtaining highly efficient fluorescent emitter, it is important to reduce the loss mechanisms such as dexter energy transfer (DET), direct charge trapping on terminal emitter by precise optimization and selection of materials. This review gives a broad overview of the development of HF-OLEDs including the device design approaches, and evolution of molecular design of the emitters for the entire range of colors. This review also provides a detailed discussion on various issues and possible solutions related to multi-resonance (MR)-TADF emitters, their molecular designs and inert peripheral substitution. These detailed insights in this review are expected to provide further impetus to the field of HF-OLEDs to enable commercial realization and application of the technology.

Janus Metasurface Hologram

A single-layer titania Janus metasurface hologram achieves directionally asymmetric imaging in the visible range. By integrating the Dammann grating principle and precise phase control, it generates high-fidelity holographic images for arbitrary polarizations, enabling compact and versatile optical technologies. More details can be found in the Research Article by Yao-Wei Huang and co-workers (DOI: 10.1002/adom.202501546).

The lighting industry has undergone significant changes over the past decade, lead-based low-dimensional metal halides exist as electroluminescent diodes (LEDs) and possess significant potential because of their external quantum efficiency (EQE) exceeding 25%. However, the lead toxicity and instability of the device hindered its commercialization. At present, an effective way to solve these problems is to replace lead (Pb²⁺) with low-toxicity or non-toxic metal ions to form lead-free metal halides. In this paper, the synthesis of recent novel low-dimensional hybrid metal halides based on Pb, Cu, Mn, Sb, Sn, etc. metals is reviewed, and their photoluminescence mechanism is discussed. From the perspective of material evolution and challenges, this summarizes the progress made in low-dimensional metal hybrid halides for white light-emitting diodes (WLEDs), and it discusses the limitations of current WLEDs materials, aiming to point out an encouraging outlook for its future development in solid-state lighting.

Doping CsPbCl₃ perovskite nanocrystals (NCs) with Mn²⁺ has gained attention due to their interesting emission properties. However, the photoluminescence (PL) spectra of these NCs display both dopant and exciton emission peaks. It is critical to achieve color purity for light–emitting diode (LED) applications, but the factors that govern this remain unclear. Herein, a systematic investigation of the factors determining the exciton-to-dopant energy transfer process in Mn²⁺-doped CsPbCl₃ NCs is presented to reveal how the exciton-to-Mn²⁺ emission ratio can be maximized. These findings indicate that this process is not only affected by dopant concentration and halide (Cl/Br) composition, but also by the co-dopants used, as well as surface passivation. These factors can potentially account for the discrepancies in the exciton-to-dopant emission ratios across the literature. These results show that post-synthetic surface passivation of Mn²⁺-doped CsPbCl₃ NCs with quaternary ammonium salt, such as dimethyldidodecylammonium chloride (DDACl), drastically enhances the exciton-to-Mn²⁺ emission ratio, achieving a two-fold increase. Ultrafast pump-probe spectroscopy surprisingly reveals that the passivation can introduce shallow trap states that enhance energy transfer to dopant sites and influence overall luminescence efficiency through non-radiative decay processes. This study sets guidelines for maximizing dopant emission in doped perovskite NCs.

Miniaturized Metalens Microscopic System

This study presents a highly compact microscopic imaging system that employs a metalens to project Hadamard mask patterns, generated by the DMD, onto microsamples such as biological cells under low-light conditions with high resolution. The corresponding modulated intensities are then processed using a single-pixel imaging algorithm to effectively reconstruct the sample image. More details can be found in the Research Article by Qihao Jin, Uli Lemmer, Xuri Yao, Qing Zhao, and co-workers (DOI: 10.1002/adom.202501310).

Quantum dot light-emitting diodes (QD-LEDs) have struggled with charge imbalance due to inefficient hole injection. Traditional strategies focus on enhancing the hole transport layer (HTL) and reducing the injection barrier at the HTL-QD interface. Although these approaches improve hole injection at specific interfaces, they fail to ensure efficient hole injection across all interfaces in QD-LEDs. Therefore, engineering the hole injection layer (HIL) is required to comprehensively address these challenges. Optimized HIL designs align the energy levels of the anode/HIL and the HTL, enable efficient hole injection, and suppress leakage current—thereby improving both performance and stability of QD-LEDs. These findings highlight the importance of comprehensive HIL engineering. In this study, a multilayered HIL structure composed of a poly(9-vinylcarbazole) (PVK): phosphomolybdic acid (PMA) layer coupled with MoO₃ is proposed. The PVK:PMA layer forms charge-transfer complexes (CTCs), enhancing hole injection into the HTL, while MoO₃ scavenges excess electrons, thereby reducing non-radiative recombination. Additionally, the high ionization potential (IP) of PVK:PMA alleviates the hole injection barrier that may arise from the MoO₃ and the organic HTL. This HIL structure doubles the power efficiency and extends the device lifetime by six times compared with conventional designs, demonstrating its potential for high-efficiency, stable QD-LEDs.