Advanced Optical Materials最新文献

A systematic investigation of the optical emission and absorption properties in nitrogen-implanted Ga₂O₃ in correlation with its polymorphic stability controlled by dynamic defect annealing is undertaken. It is demonstrated that dynamic annealing processes, determined by the irradiation temperatures, significantly influence both disorder accumulation and phase transformations in β-Ga₂O₃, in turn, leading to a modulation of the absorption and emission properties of the implanted material. Specifically, room-temperature implantation induces β-to-γ phase transitions, accompanied by an enhancement of the characteristic green luminescence (GL) band. In contrast, implantation at elevated temperatures suppresses γ-phase formation and promotes the emergence of strong red luminescence (RL) emission. The results are interpreted within the framework of competing effects between defects generated during the β-to-γ phase transformation and the incorporation of implanted nitrogen atoms. The presented findings contribute to a deeper understanding of dopant-defect interactions in Ga₂O₃ as well as modulation of the optical properties of its polymorphs.

The optical encryption strategy based on the combination of fluorescence and polarization holography has significant advantages in multi-dimensional coding and visual security, and plays a crucial role in information protection. However, building a robust dual-functional platform with full-color fluorescence tunability and large storage capacity still remains a big challenge. Herein, fluorescent carbon dots (CDs) are assembled into gridded titania (TiO₂) scaffolds for ultra-high-level holographic encryption. The construction of the fluorescence-holography encryption layer utilizes both the polarized spectral hole-burning of CDs/TiO₂ based on directional interface charge transfer and the fluorescence emission characteristics of CDs monomers. Chromaticity information is assigned to Quick Response (QR) code patterns under UV excitation. Then, micrometric computer-generated holograms (CGHs) are written into the CDs/TiO₂ region, which exhibits significant polarization dependence. The decryption of true information requires the super verification with color, coordinate, polarization, wavelength, and logical judgment. The platform demonstrates excellent optical and thermal stability, maintaining over 97% fluorescence intensity under prolonged UV irradiation, and persistent holographic reconstruction efficiency at 433 K for at least 30 h. This work integrates color display, fluorescence switch, and polarization holography, providing a promising path for high-security optical anti-counterfeiting and information encryption.

Zero-dimensional (0D) organic–inorganic hybrid halides are emerging as promising lead-free emissive materials. However, growing their high-quality single crystals remains a formidable challenge, primarily due to uncontrolled nucleation and complex phase competition. Herein, a facile and eco-friendly single-heat-source crystallization strategy is reported for the controllable growth of high-quality MA₄InCl₇:Sb³⁺ single crystals. The establishment of an axial temperature gradient promotes directional solute diffusion and Ostwald ripening, enabling spontaneous transformation from precursors to large transparent crystals. Structural analysis reveals that the asymmetric coordination environment and intrinsic low crystal symmetry facilitate selective nucleation and stable crystal growth. The grown transparent crystals exhibit intense yellow emission with a remarkable photoluminescence quantum yield (PLQY) of up to 92.86%, originating from self-trapped excitons (STEs) within isolated [SbCl₆]³⁻ octahedra. The high optical quality and uniformity are further demonstrated by the fabrication of a bright yellow-emitting LED, showing its potential in phototherapy-related applications. This work not only provides a green and efficient pathway for synthesizing hybrid halide single crystals but also offers new insights into thermodynamics-influenced selective crystallization associated with intrinsic low-symmetry structural preferences.

Wearable organic photodetectors (OPDs) operating in the near-infrared (NIR) are pivotal for non-invasive photoplethysmography (PPG)-based health diagnostics. Yet, their practical deployment is impeded by excessive dark current density (J_d) and poor stability. Here, it is demonstrated that strategic interfacial engineering—inserting an ultrathin Au interlayer atop the alcohol-soluble polyelectrolyte (PFN-Br)—simultaneously suppresses J_d and fortifies device stability. The new interfacial layer with lower defect density reduces non-radiative recombination and elevates the electron-injection barrier, suppressing J_d to 1.12 × 10⁻¹⁰ A cm⁻² (at 0.1 V) and affording a record specific detectivity (D^*) of 8.76 × 10¹³ Jones at 860 nm. Concurrently, the ITO/PFN-Br/Au stack cooperates with the MoO₃/Ag top mirror to establish an optical microcavity that red-shifts the spectral response by ≈50 to 860 nm, perfectly matching the hemoglobin isosbestic point for oxygen saturation level (SpO₂) monitoring. Integrating the optimized OPD into a lightweight convolutional-neural-network (DESNet) platform yields accurate, cuff-less blood-pressure estimation (R² = 0.81 for diastolic pressure) and SpO₂ readings that agree within ±2% of clinical gold standards. This work provides a universal design paradigm for high-D^*, stable OPDs and validates their translational potential in wearable multi-parameter health surveillance.

Since the groundbreaking demonstration one decade ago, metasurfaces have widely reformed applications with continuously extended scopes. Somewhat unexpectedly, traditional metasurfaces are usually confronted with problems of challenging fabrications due to the large height/width aspect ratio of unit cells to cover full phase range. Here, a concept of geometrically compensated phase is introduced. A microscale grating as primary structure is designed to provide π phase compensation, and the unit cells as secondary structure are only required to provide a phase delay of 0–π. As proofs-of-concept, beam deflection and focusing are demonstrated with all-glass hierarchical metasurfaces. It is found that the metasurface beam deflectors maintain high efficiencies, while the maximum aspect ratio of the unit cell is significantly reduced from 23.4 and 30 to 8.4 and 8.7 by up to 71% for 5.04° and 3.78° beam deflectors, respectively. Furthermore, numerical investigations verify the hierarchical metasurfaces present good robustness to fabrication errors. The dependences of the proposed metasurfaces on the incident angle, operation wavelength, and grating height are analyzed quantitatively. The near-diffraction-limited focusing confirms the generic capability of this hierarchical metasurface besides beam deflections. This work represents an accessible design strategy for metasurfaces with broad material compatibility and promotes the advances of metasurfaces.

Plasmonic-based metasurfaces play a crucial role in resonance-driven photocatalytic reactions by effectively enhancing reactivity via localized surface plasmon resonances. Catalytic activity can be modulated by tuning the strength of plasmonic resonances in two primary nonthermal mechanisms: near-field enhancement and hot-carrier injection, which govern the population of energetic carriers excited or injected into unoccupied molecular orbitals. A set of polarization-sensitive metasurfaces consisting of elliptical Au-TiO₂ nanopillars, specifically designed to plasmonically modulate the reactivity of a model reaction: the photocatalytic degradation of methylene blue, is developed. Surface-enhanced Raman spectroscopy allows to indirectly assess the yield by monitoring the product peak and shows polarization-dependent yield rate modulated by a factor of 2 depending on the polarization – either x-/y-polarization in 10 s period, as quantified by the integrated area of the 480 cm⁻¹ Raman peak and correlated with enhanced absorption at 633 nm. The single metasurface configuration enables continuous tuning of photocatalytic reactivity via active control of plasmonic resonance strength, as evidenced by the positive correlation between measured absorption and indicative product yield. This dynamic approach provides a route to tailor-enhance or suppress resonance-driven reactions, which can be further leveraged to achieve in multibranch reactions, guiding product yields toward desired outcomes.

The precise tailoring of bandgap structures as well as carrier separation and transport behavior via heterojunction engineering can provide a practical and viable pathway for enhancing the performance of low-dimensional semiconductor devices. In this study, a highly photosensitive photoelectrochemical (PEC) ultraviolet (UV) photodetector (PD) based on a SiC/ZnO heterojunction is explored. The surfaces of SiC nanowires are successfully modified using high-quality ZnO nanospheres via a simple hydrothermal process. The as-constructed SiC/ZnO heterojunction nanowire PEC UV PD achieves high photodetection performance—high responsivity (15.76 mA W⁻¹), high detectivity (1.827 × 10¹⁰ Jones), excellent external quantum efficiency (5.21%), and fast rise/decay times (186/454 ms), under 375-nm UV illumination. Remarkably, the device exhibits a high photoresponse under different solution concentrations, temperature conditions, and excellent aging stability over long-term operation. Its highly sensitive and reliable photodetection performance could be attributed primarily to the synergy among the type-II charge transfer pathways formed at the SiC/ZnO heterojunction, enhanced photogenerated-carrier separation efficiency, and improved light–matter interactions enabled by the large specific surface area of the ZnO nanospheres. Overall, this study establishes a paradigm for developing highly sensitive PEC PDs suitable for optical communication under harsh underwater conditions, thereby advancing heterojunction and interfacial engineering strategies for next-generation optoelectronics.

In the quest for efficient photocatalysts, cancrystal shape engineering outperform size reduction in enhancing photocatalytic performance? This is investigated using CsPbBr₃ perovskite nanocrystals (PNC) by comparing conventional amine-capped, 6-facet cubic morphology with newly developed 26-facet polyhedral nanocrystals synthesized via an amine-free approach. Surprisingly, the larger polyhedral PNCs are far better at converting CO₂ into CO, despite their lower surface-to-volume ratio than the 6-facet cubic PNCs. They achieve a total CO yield of 394 µmol g⁻¹ with a conversion rate of 35.81 µmol g⁻¹ h⁻¹ without any help from extra co-catalysts. To the best of the author's knowledge, this represents the highest reported CO evolution rate using 3-dimensional PNCs as the sole photocatalyst, with performance comparable to or exceeding systems employing co-catalysts. This enhanced activity arises from longer excited-state lifetimes, improved charge transport, larger electrochemical surface area (ECSA), and a higher density of charge carriers, as confirmed by optical and electrochemical studies. Computational studies show that some specific facets of this polyhedra bind CO₂ molecules more strongly and provide the optimized binding energy to efficiently release the final product(CO). With excellent 12-h stability, these shape-controlled nanocrystals enable a pathway toward sustainable energy technology applications worldwide.

Despite significant progress in the development of Cr³⁺-activated near-infrared (NIR) phosphors, achieving highly efficient, thermally stable, and cost-effective NIR phosphors remains a challenge. In this work, the Lu_3-xCa_xAl_5-xSi_xO₁₂:0.05Cr³⁺ (CaxLAS:0.05Cr³⁺, 0 ≤ x ≤ 1.5) solid-solution phosphors are synthesized through neighboring cation co-substitution (Lu³⁺ + Al³⁺ → Ca²⁺ + Si⁴⁺). Structural Rietveld refinement, electron paramagnetic resonance, and fluorescence decay analyses confirm that the co-substitution indirectly relaxes the [(Al/Cr)O₆] octahedral framework, enabling a dramatic transition in Cr³⁺ emission from deep-red sharp-line spectra (687 nm) to broadband NIR emission (766 nm), while the full width at half maximum broadens from 25 to 172 nm. Notably, the external quantum efficiency (EQE) increases from 4.52% to 23.5%. These are attributed to the change in the mode of transition from the spin-forbidden ²E_g → ⁴A_2g to the spin-allowed ⁴T_2g → ⁴A_2g and the formation of Cr³⁺ pairs. Furthermore, by introducing Ce³⁺ as a sensitizer, an EQE of 45.6% is achieved in the optimized Ca1.5LAS:0.08Ce³⁺,0.05Cr³⁺ composition. The phosphor retains 69.5% of its initial photoluminescence intensity at 427 K, demonstrating good thermal stability. This work not only develops a high-performance solid-solution phosphor for applications in non-destructive testing and silicon solar cell efficiency enhancement but also highlights strategic approaches for advancing NIR phosphor design.

Noninvasive/contact palm-vein recognition utilizes near-infrared (NIR) illumination to highlight subcutaneous venous patterns, enabling deep-tissue imaging with high resolution and improved contrast, binocular dual-spectral imaging representing a breakthrough in biometric identification. Narrow bandgap Sn-Pb perovskites have recently emerged as potential sensing materials that may outperform conventional NIR counterparts. However, the instability, nonuniform large-scale pixel array fabrication, as well as crosstalk greatly hinders high-quality imaging. Here, a novel binocular imaging system that combines fast self-powered visible (VIS)/NIR perovskite photodetectors with advanced computational algorithms is proposed. To date, it features exceptional imaging speed of 2.9 µs, a record-low detection limit of 7.64 nW cm⁻². Meanwhile, the NIR photodetectors (PDs) are applicable to convert transmission NIR light to photovoltage. By integrating the anti-scattering merit of single-pixel imaging with deep penetration of infrared light in tissue, high-performance binocular computational imaging in diffuse reflection and projection modes has been achieved for the first time. Furthermore, fast noncontact palmprint and palm-vein recognition imaging are successfully demonstrated within 1 s. This work offers a promising new direction for perovskite-based NIR imaging, advancing the development of more reliable and detailed imaging capabilities.