Bi-Hsuan Lin

We report the first experimental observation of grazing-incidence X-ray back-diffraction (GIXBD) exhibiting exceptionally large angular dispersion. An angular dispersion rate (ADR) of 44.4 ± 9.3 µrad meV ⁻¹ was measured from a Si (12 4 0) crystal with a surface miscut angle of 89.926°, representing the largest ADR reported for X-ray back-diffraction. The observed diffraction behaviour is quantitatively reproduced by the full dynamical theory of X-ray diffraction. A kinematic formulation based on Snell's law provides a simple geometrical interpretation of the grazing-incidence limit beyond the conventional DuMond analysis and predicts a large but finite ADR, thereby avoiding the apparent divergence of the conventional treatment. These results provide the first experimental validation of GIXBD, establish a physically consistent description of angular dispersion in the extreme grazing-incidence limit and provide a sound physical basis for future ultra-high-resolution crystal X-ray optics.

The emission of a luminescent material is governed not only by the centers it contains but by how they are excited, a distinction that becomes decisive when several emitting phases coexist. Eu- and Dy-doped strontium aluminates, the most widely used persistent-luminescence phosphors, are frequently multiphase, which complicates the assignment of their emission. Here, a mixed-phase Eu,Dy-doped strontium aluminate ceramic, with estimated phase fractions of 71.4% SrAl2O4 and 28.6% Sr4Al14O25 from powder X-ray diffraction, is characterized at the Taiwan Photon Source 23A hard X-ray nanoprobe by X-ray-excited optical luminescence (XEOL) spectroscopy and mapping, X-ray fluorescence (XRF) mapping, and X-ray absorption spectroscopy (XAS). The dominant spectral contributions depend on the excitation channel: under 9670 eV excitation the XEOL is dominated by a 493 nm Eu2+ band characteristic of the minority Sr4Al14O25 phase, whereas ultraviolet (UV)-excited photoluminescence (PL) is dominated by the 519 nm band characteristic of the majority SrAl2O4 host. Because broadband hard X-ray excitation is less site-selective than direct UV excitation, XEOL additionally reveals Eu3+ and Dy3+ lines scarcely visible in PL and sharp Cr3+-related emission near 692–694 nm, and XAS supports these oxidation-state assignments. Energy-dispersive XRF detected trace Mn, whose K-edge absorption profile was most consistent with Mn2+, although no Mn2+ emission was resolved. A weak violet band near 408 nm is tentatively assigned to an F-type color center, although a second-site Eu2+ contribution cannot be excluded. This approach resolves multiple emission features in a multiphase phosphor and demonstrates excitation-dependent spectral weighting consistent with different phase contributions.

Photodetectors are essential optoelectronic components for biotechnological sensing and optical communication systems. Perovskite materials, owing to their broad spectral absorption, high charge-carrier mobility, mechanical flexibility, and solution processability, have emerged as promising candidates for next-generation photodetection. In this work, a block copolymer composed of polydimethylsiloxane (PDMS) and maltotriose is introduced as an interfacial modifier to regulate the crystallographic, morphological, and optoelectronic properties of perovskite thin films, thereby enhancing phototransistor performance, particularly under weak-light conditions. Copolymers with different architectures exhibit distinct surface energies, enabling efficient charge transfer between perovskite polycrystalline grains and hydroxy-rich carbohydrate segments, which effectively shortens exciton lifetimes and suppresses recombination. Notably, perovskite phototransistors incorporating a two-armed branched PDMS-block-maltotriose achieve the highest device performance under 455 nm illumination. Even at an ultralow light intensity of 0.20 μW cm–2, the device exhibits a responsivity of 0.37 A W–1 and a detectivity of 4.0 × 109 Jones, demonstrating excellent sensitivity. This performance enhancement is attributed to PDMS-directed microphase separation that spatially accommodates perovskite nanocrystals within the carbohydrate matrix, where abundant hydroxy groups passivate surface defects through hydrogen bonding or Pb2+ coordination. These results highlight the potential of block-copolymer/perovskite nanohybrids for high-performance weak-light phototransistors.

Persistent luminescence (PersL) in inorganic phosphors is typically achieved by incorporating metal-ion activators into a host lattice. Zinc germanate, Zn2GeO4 (ZGO), which has been widely used as a host for activator-doped PersL phosphors, has recently been found to exhibit intrinsic, self-activated PersL without any dopant. Despite its intriguing nature, the underlying mechanism for this activator-free PersL remains poorly understood. Previous studies have suggested a strong dependence of PersL on stoichiometry-driven defects, but investigations have been limited to asymmetric compositional tuning (either by adding excess Zn to make it Zn-rich, or by adding excess Ge to make it Ge-rich). Direct, element-specific correlations between defects and emission have remained elusive. In this paper, we present a systematic study of self-activated PersL in ZGO by spanning both Zn-rich and Zn-deficient regimes relative to the stoichiometric compositions. We show that even slight deviations in Zn/Ge ratio generates distinct defect configurations, leading to drastic differences in photoluminescence (PL) and PersL, despite nearly identical crystal structures. Notably, we identify a previously unrecognized red PersL band in stoichiometric and Zn-deficient ZGO, which is absent under photoexcitation and emerges only at delayed stages of the afterglow. By combining element-selective X-ray excited optical luminescence (XEOL) and Extended X-ray absorption fine structure (EXAFS) spectroscopy, we establish direct correlation between emission features with their elemental origins. These results provide the first element-resolved insight into defect-mediated PersL in ZGO, revealing how stoichiometry governs competing recombination pathways and enabling a more complete understanding of self-activated persistent luminescence.

Charge-transfer (CT)-based supramolecular systems have attracted considerable interest as electret materials for organic memory devices. However, uncontrolled dopant distribution, limited host–guest compatibility, and the formation of leakage pathways often compromise their morphological stability and memory performance. In this work, carbohydrate-based block copolymers (BCPs), maltotriose-block-poly(1-pyrenemethyl methacrylate) (PPy) and maltotriose-block-poly(benzyl methacrylate) (PB), are employed as supramolecular hosts for incorporating the electron acceptor F4-TCNQ, forming a series of supramolecular electret systems for organic phototransistor memory applications. Photoluminescence and time-resolved photoluminescence characterizations confirm efficient photoinduced intermolecular CT interactions in the PPy/F4-TCNQ systems, as evidenced by significant fluorescence quenching and a shortened excited-state lifetime. More importantly, solvent-vapor annealing induces supramolecular reorganization within the electret layer, thereby effectively regulating dopant distribution and reducing leakage pathways. Meanwhile, optical, morphological, and surface-energy analyses further reveal that the maltotriose carbohydrate block plays a critical role in suppressing channel interference and stabilizing the supramolecular architecture. As a result, the optimized phototransistor memory exhibits a high photosensitivity of 1.27 × 107 and a memory ratio of 1.61 × 106. Furthermore, reliable memory operation is maintained under low-light-intensity (0.01 mW cm–2) and low-operating-voltage (−0.1 V) conditions. These findings demonstrate that carbohydrate-based BCPs provide an effective platform for integrating CT supramolecular interactions with controllable dopant organization, offering a versatile molecular design strategy for developing high-performance organic photomemory devices.

Bidentate ligand engineering provides a versatile strategy to regulate crystallization and lattice dynamics in metal halide perovskites. Herein, a bidentate malonamide ligand, butyl-malonamide-phenylene (Bi-BMP), is incorporated into red 2D/quasi-2D/3D perovskites (PVSK) to construct efficient exciton-funneling channels and enhance crystal rigidity. The malonamide groups form strong dipole–ion coordination with Pb2+, promoting uniform phase growth and balanced dimensional distribution, while the rigid phenylene backbone suppresses thermal lattice expansion and field-induced distortion. These dual functions yield reduced exciton–phonon coupling (γLO = 130 meV) and suppressed nonradiative recombination, resulting in a sixfold enhancement of solid-film PLQY (26.9%). Consequently, Bi-BMP@PVSK devices achieve an EQE of ≈14%, a tenfold longer operational lifetime, and color-pure red emission (CIE 0.623, 0.260) approaching the Rec. 2020 standard. This dual-functional molecular design establishes a general strategy for highly efficient and durable red PeLEDs.

Wolframite Nickel Tungstate (NiWO4) with good crystallinity was synthesized via a facile coprecipitation method and evaluated for its electrochemical performance in various aqueous electrolytes, including acidic media (HCl, H2SO4), alkaline media (NaOH, KOH), and neutral media (KCl, NaCl, Na2SO4, K2SO4). The crystallinity and wolframite structure of the as-prepared NiWO4 were confirmed and analysed using XRD, Raman, and FTIR. The morphological studies of NiWO4 were done via Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), revealing that the nanoparticles are slightly agglomerated. The electrochemical evaluation was performed to discuss the effect of various aqueous electrolytes and their interaction with the electrode. Based on the Hofmeister theory of classification (Chaotropic and Kosmotropic ions), ion-specific interaction in the electrode-electrolyte interface and its effect on electrochemical properties are investigated. The X-ray Fluorescence mapping and X-ray Absorption studies were employed for studying the elemental distribution and site-based electronic structure of NiWO4, respectively. Thus, the NiWO4 is a pseudocapacitive material, and its maximum specific capacitance of 216 F g-1 was achieved in a KCl electrolyte in comparison with the other electrolytes.

Perovskite light-emitting diodes (PeLEDs) have emerged as promising candidates for next-generation display and lighting technologies due to their high photoluminescence quantum yield, tunable emission characteristics, and narrow spectral bandwidth. However, achieving efficient and stable blue emission remains a significant challenge, primarily due to poor phase purity, excessive trap density, and unfavorable energy level alignment. Herein, we propose a dual-functional molecular engineering strategy utilizing 4-guanidinobenzoic acid hydrochloride (GBAC) as both a buried interfacial layer and a bulk additive. When employed at the buried interface, GBAC enhances surface wettability and precursor spreading, thereby improving film morphology and crystallinity. This additional layer also helps optimize energy level alignment between the hole transport layer and the perovskite emissive layer, reducing the injection potential barrier. Simultaneously, when acting as an additive in the bulk phase, GBAC's guanidinium group binds to undercoordinated Pb²⁺ trap states via electrostatic coordination, suppressing nonradiative recombination; while its carboxylic group forms hydrogen bonds with the ammonium end of phenethylammonium bromide, reducing the formation of low-n (n = 1-2) phases and promoting growth in the medium-to-high n-value domains, thereby enhancing energy funneling efficiency. Leveraging these advantages, the device fabricated with dual GBAC treatment exhibits enhanced spectral stability, reduced turn-on voltage, and achieves an external quantum efficiency of up to 10.6% in the sky-blue emission band (∼489 nm), representing a > 60% improvement over the pristine device.