Search Results (180)

Zero-dimensional (0D) rare-earth-based metal halides show great potential in photonic and optoelectronic applications owing to their high stability, strong exciton confinement, and tunable energy levels. However, the weak absorption and narrow 4f-4f transitions of rare-earth ions limit their performance. To address this, a series of Sb³⁺-doped Cs₃LnCl₆ (Ln: Yb, La, Eu, Ho, Ce, Er, Tb, Sm, Y) nanocrystals were synthesized via a hot-injection method to study the role of Sb³⁺ doping. Sb³⁺ incorporation induces strong broadband self-trapped exciton (STE) emission from Jahn–Teller-distorted [SbCl₆]³⁻ units and enables efficient energy transfer from STEs to rare-earth ions. As a result, the photoluminescence intensity and spectral tunability are improved, accompanied by bandgap narrowing and enhanced light absorption. Different lanthanide hosts exhibit distinct luminescence behaviors: La-based materials show dominant STE emission, while Tb-, Er-, Yb-, Ho-, and Sm-based systems display STE-mediated energy transfer and enhanced f-f emission. In Eu- and Ce-based hosts, unique mechanisms involving Eu²⁺/Eu³⁺ conversion and Ce³⁺ → STE energy transfer are observed. Moreover, composition-dependent emissions in Sb³⁺-doped Cs₃Tb/EuCl₆ enable a dual-mode color and spectral encoding strategy for optical anti-counterfeiting. This study highlights the versatile role of Sb³⁺ in tuning electronic structures and energy transfer, offering new insights for designing high-performance rare-earth halide materials for advanced optoelectronic applications. Full article

This work investigates a comprehensive temperature-dependent photoluminescence (PL) study (7–300 K) of β-Ga₂O₃ single crystals under 250 nm excitation. The emission consists of three competing bands at ~3.55 eV (J₁), ~3.37 eV (J₂), and ~3.07 eV (J₃), exhibiting a redshift, band broadening, and a crossover near ~140 K with increasing temperature. The novelty of this study lies in the first quantitative investigation of the temperature-dependent photoluminescence of undoped β-Ga₂O₃ single crystals, revealing activation, trap-release, and phonon-coupling parameters that define the competition between STE (Self-trapped exciton)- and DAP-related emission channels. A two-channel Arrhenius analysis of global thermal quenching at E_max (at maximum PL), J₁, and J₂ reveals a common shallow barrier (E₁ = 7–12 meV) alongside deeper, band-specific barriers (E₂ = 27 meV for J₁ and 125 meV for J₂). The J₃ band shows non-monotonic intensity (dip–peak–quench) reproduced by a trap-assisted generation model with a release energy E_rel = 50 meV. Linewidth analysis yields effective phonon energies (E_ph ≈ 40–46 meV), indicating strong electron–phonon coupling and a transition to multi-phonon broadening at higher temperatures. These results establish a coherent picture of thermally driven redistribution from near-edge STE-like states to deeper defect centers and provide quantitative targets (activation and phonon energies) for defect engineering in β-Ga₂O₃-based optoelectronic and scintillation materials. Full article

Understanding how solvents influence the luminescence behavior of Cu(I) complexes is crucial for designing advanced optical sensors. This study reports the synthesis, structures and photophysical investigation of an 8-hydroxyquinoline-functionalized 1H-imidazo[4,5-f][1,10]phenanthroline ligand, ipqH₂, and its four Cu(I) complexes with diphosphine co-ligands. Photoluminescence studies demonstrated distinct solvent-dependent excited-state mechanisms. In DMSO/alcohol mixtures, free ipqH₂ exhibited excited-state proton transfer (ESPT) and enol-keto tautomerization, producing dual emission at about 447 and 560 nm, while the complexes resisted ESPT due to hydrogen bond blocking by PF₆⁻ anions and Cu(I) coordination. In DMSO/H₂O, aggregation-caused quenching (ACQ) and high-energy O–H vibrational quenching dominated, but complexes 1 and 2 showed a significant red-shifted emission (569–574 nm) with high water content due to solvent-stabilized intra-ligand charge transfer and metal-to-ligand charge transfer ((IL+ML)CT) states. In DMSO/DMF, hydrogen bond competition and solvation-shell reorganization led to distinct responses: complexes 1 and 3, with flexible bis[(2-diphenylphosphino)phenyl]ether (POP) ligands, displayed peak splitting and (IL + ML)CT redshift emission (501 ⟶ 530 nm), whereas complexes 2 and 4, with rigid 9,9-dimethyl-4,5-bis(diphenylphosphino)-9H-xanthene (xantphos), showed weaker responses. The flexibility of the diphosphine ligand dictated DMF sensitivity, while the coordination, the hydrogen bonds between PF₆⁻ anions and ipqH₂, and water solubility governed the alcohol/water responses. This work elucidates the multifaceted solvent-responsive mechanisms in Cu(I) complexes, facilitating the design of solvent-discriminative luminescent sensors. Full article

We present a systematic study of the fundamental optical properties of indium selenide (InSe) single crystals over a temperature range of 17 K to 300 K. The high structural quality of the β-polytype crystals was confirmed through X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy, demonstrating excellent crystallinity and a nearly stoichiometric In:Se ratio. The temperature-dependent absorption and photoluminescence (PL) spectra are characterized by a prominent free exciton (FX) resonance. At 17 K, the photoluminescence spectrum exhibits a distinct fine-structure splitting of the Wannier–Mott exciton, yielding a triplet state at 1.333 eV and a singlet state at 1.336 eV. Additionally, a biexciton (XX) is localized at an energy of 1.322 eV as confirmed by the nonlinear dependence of intensity on excitation power density. At low temperatures, the absorption spectrum exhibits the free exciton ground state (n = 1) at 1.338 eV together with the first excited state (n = 2) at 1.350 eV. We systematically tracked and analyzed the temperature evolution of these quasiparticle energies. These findings enhance our understanding of the intrinsic many-body interactions in high-quality InSe, providing essential parameters for advancing its applications in innovative optoelectronic and quantum light-emitting devices. Full article

One-dimensional GaAs/InGaAs core–shell nanowires (NWs) with reverse type-I band alignment are promising candidates for next-generation optoelectronic devices. However, the influence of composition gradients and atomic interdiffusion at the core–shell interface on their photoluminescence (PL) behavior remains to be clarified. In this work, GaAs/In_xGa_1−xAs NW arrays with different indium (In) compositions were prepared using molecular beam epitaxy (MBE), and their band alignment and optical responses were systematically investigated through power and temperature-dependent PL spectra. The experiments reveal that variations in the In concentration gradient modify the characteristics of potential wells within the composition graded layer (CGL), as reflected by distinct PL emission features and thermal activation energies. At elevated temperatures, carrier escape from these wells is closely related to the observed PL saturation and emission quenching. These results provide experimental insight into the relationship between composition gradients, carrier dynamics, and emission properties in GaAs/InGaAs core–shell NWs, making them promising candidates for high-performance nanoscale optoelectronic device design. Full article

Structure–property relationships in imidazolium-based hybrid Sb(III) chlorides provide critical guidance for designing high-performance materials. Three zero-dimensional metal halides, namely, [C₃mmim]₂SbCl₅ (1, [C₃mmim]⁺ = 1-propyl-2,3-dimethylimidazolium), [C₅mmim]₂SbCl₅ (2, [C₅mmim]⁺ = 1-pentyl-2,3-dimethylimidazolium), and [C₅mim]₂SbCl₅ (3, [C₅mim]⁺ = 1-pentyl-3-methylimidazolium), are synthesized by ionothermal methods. These compounds exhibit markedly distinctly photophysical properties at their optimal excitation wavelengths. Structural analyses reveal that elongated alkyl chains in compounds 2 and 3 increase Sb–Sb distances compared to that in 1, effectively isolating [SbCl₅]²⁻ units, suppressing inter-center energy transfer, and reducing non-radiative transitions, thereby enhancing the photoluminescence quantum yield (PLQY). Furthermore, methyl substitution at the C2-position of the imidazolium ring in compounds 1 and 2 induces asymmetric coordination environments around the [SbCl₅]²⁻ emission centers, leading to pronounced structural distortion. This distortion promotes non-radiative decay pathways and diminishes luminescent efficiency. Furthermore, temperature-dependent spectroscopy analysis and fitting of the Huang–Rhys factor (S) reveal significant electron–phonon coupling in compounds 1–3, which effectively promotes the formation of self-trapped excitons (STEs). However, compound 1 exhibits extremely high S, which significantly enhances phonon-mediated non-radiative decay and ultimately reduces its PLQY. Overall, compound 3 has the highest PLQYs. Full article

We report the development of highly luminescent, bovine serum albumin (BSA)-stabilized gold–silver bimetallic nanoclusters (Au-AgNCs@BSA) as a novel platform for high-sensitivity, ratiometric intracellular temperature sensing. Precise and non-invasive temperature sensing at the nanoscale is crucial for applications ranging from intracellular thermogenesis monitoring to localized hyperthermia therapies. Traditional luminescent thermometric platforms often suffer from limitations such as high cytotoxicity and low photostability. Here, we synthesized Au-AgNCs@BSA via a one-pot aqueous reaction, achieving significantly enhanced photoluminescence quantum yields (PL QYs, up to 18%) and superior thermal responsiveness compared to monometallic counterparts. The dual-emissive Au-AgNCs@BSA exhibit a linear ratiometric fluorescence response to temperature fluctuations within the physiological range (20–50 °C), enabling accurate and concentration-independent thermometry in live cells. Time-resolved PL and Arrhenius analyses reveal two distinct emissive states and a high thermal activation energy (E_a = 199 meV), indicating strong temperature dependence. Silver doping increases radiative decay rates while maintaining low non-radiative losses, thus amplifying fluorescence intensity and thermal sensitivity. Owing to their small size, excellent photostability, and low cytotoxicity, these nanoclusters were applied to non-invasive intracellular temperature mapping, presenting a promising luminescent nanothermometer for real-time cellular thermogenesis monitoring and advanced bioimaging applications. Full article

Perovskite solar cells (PSCs) are emerging as leading candidates for sustainable energy generation due to their high power conversion efficiencies and low fabrication costs. However, their performance remains constrained by non-radiative recombination losses primarily at grain boundaries, interfaces, and within the perovskite bulk that are difficult to characterize under realistic operating conditions. Traditional methods such as photoluminescence offer valuable insights but are complex, time-consuming, and often lack scalability. In this study, we present a novel Long Short-Term Memory (LSTM)-based deep learning framework for dynamically predicting dominant recombination losses in PSCs. Trained on light intensity-dependent current–voltage (J–V) characteristics, the proposed model captures temporal behavior in device performance and accurately distinguishes between grain boundary, interfacial, and band-to-band recombination mechanisms. Unlike static ML approaches, our model leverages sequential data to provide deeper diagnostic capability and improved generalization across varying conditions. This enables faster, more accurate identification of efficiency limiting factors, guiding both material selection and device optimization. While silicon technologies have long dominated the photovoltaic landscape, their high-temperature processing and rigidity pose limitations. In contrast, PSCs—especially when combined with intelligent diagnostic tools like our framework—offer enhanced flexibility, tunability, and scalability. By automating recombination analysis and enhancing predictive accuracy, our framework contributes to the accelerated development of high-efficiency PSCs, supporting the global transition to clean, affordable, and sustainable energy solutions. Full article

This study presents the fabrication and characterization of ZnO–CNT composite-based optoelectronic synaptic devices via a sol–gel process. By incorporating various concentrations of CNTs (0–2.0 wt%) into ZnO thin films, we investigated their effects on synaptic behaviors under ultraviolet (UV) stimulation. The CNT addition enhanced the electrical and optical performance by forming a p–n heterojunction with ZnO, which promoted charge separation and suppressed recombination. As a result, the 1.5 wt% CNT device exhibited the highest excitatory postsynaptic current (EPSC), improved paired-pulse facilitation, and prolonged memory retention. Learning–forgetting cycles revealed that repeated stimulation reduced the number of pulses required for relearning while extending the forgetting time, mimicking biological memory reinforcement. Energy consumption per pulse was estimated at 16.34 nJ, suggesting potential for low-power neuromorphic applications. A 3 × 3 device array was also employed for visual memory simulation, showing spatially controllable and stable memory states depending on CNT content. To support these findings, structural and optical analyses were conducted using scanning electron microscopy (SEM), UV-visible absorption spectroscopy, photoluminescence (PL) spectroscopy, and Raman spectroscopy. These findings demonstrate that the synaptic characteristics of ZnO-based devices can be finely tuned through CNT incorporation, providing a promising pathway for the development of energy-efficient and adaptive optoelectronic neuromorphic systems. Full article

Upscaling perovskite solar cells and modules requires precise laser patterning for series interconnection and spatial characterization of cell parameters to understand laser–material interactions and their impact on performance. This study investigates the use of nanosecond (ns) and picosecond (ps) laser pulses at varying fluences for the P3 patterning step of perovskite solar cells. Hyperspectral photoluminescence (PL) imaging was employed to map key parameters such as optical bandgap energy, Urbach energy, and shunt resistance. The mappings were correlated with electrical measurements, revealing that both ns and ps lasers can be utilized for effective series interconnections with minimal performance losses at optimized fluences. Our findings provide a deeper understanding of fluence-dependent effects in P3 patterning. Moreover, the results demonstrate that the process window is robust, allowing for reasonable cell performance even with deviations from optimal parameters. This robustness, coupled with the scalability of the laser patterning process, emphasize its suitability for industrial module production. Full article

Recent advances in electrochemiluminescence (ECL) leveraging thermally activated delayed fluorescence (TADF) have highlighted its potential for near-unity exciton harvesting. However, there are still very limited examples of TADF-ECL emitters. We present a rigid diboron-embedded multiple-resonance TADF emitter, which exhibits blue–green emission at 493 nm with a remarkably narrow bandwidth (FWHM = 22 nm) and minimized singlet-triplet energy gap (ΔE_ST = 0.2 eV), achieving a 67% photoluminescence quantum yield. DFT calculations confirm the short-range charge transfer, enabling narrowband emission. Co-reactant-dependent ECL shows that tripropylamine (TPrA) improves the ECL efficiency from 11% (annihilation) to 51%, while benzoyl peroxide (BPO) yields 1% due to poor radical stabilization. ECL spectra align with photoluminescence, confirming the singlet-state dominance without exciplex interference. TPrA enhances stable radical formation and energy transfer, whereas BPO induces non-radiative losses. These findings establish molecular rigidity and co-reactant selection as pivotal factors in developing high-performance TADF-ECL systems, providing fundamental guidelines for designing organic electrochemiluminescent materials with optimized exciton harvesting efficiency. Full article

In order to break through the limitations of the application of traditional temperature measurement technology, non-contact optical temperature sensing material with good sensitivity is one of the current research hotspots. Herein, a series of Dy³⁺ and Mn⁴⁺ co-doping Mg₃Ga₂SnO₈ fluorescent materials were prepared successfully, and the crystal structure, phase purity, and morphology of the synthesized phosphors were comprehensively investigated, as well as their photoluminescence properties, energy transfer, and high-temperature thermal stability. The two pairs of independent thermally coupled energy levels of Dy³⁺ ions and Mn⁴⁺ ions in Mg₃Ga₂SnO₈ are utilized to realize the dual-mode optical temperature detection with excellent performance. On the one hand, based on the different ionic energy level transitions of ⁴F_9/2→⁶H_13/2 and ²E_g→⁴A_2g responding differently to temperature, two emission bands of 577 nm and 668 nm were chosen to construct the fluorescence intensity ratio thermometry, and the maximum sensitivity of 1.82 %K⁻¹ was achieved at 473 K. On the other hand, based on the strong temperature dependence of the lifetime of Mn⁴⁺ in Mg₃Ga₂SnO₈:0.06Dy³⁺,0.009Mn⁴⁺, fluorescence lifetime thermometry was constructed and a maximum sensitivity of 2.75 %K⁻¹ was achieved at 473 K. Finally, the Mg₃Ga₂SnO₈: 0.06Dy³⁺,0.009Mn⁴⁺ sample realizes dual-mode optical temperature measurement with high sensitivity and a wide temperature detection range, indicating that the sample has promising applications in optical temperature measurement. Full article

Triplet–triplet transfer photochemical reactions are essential in many biological, chemical, and photonic applications. Here, the Pd-octaethylporphyrin sensitizer along with triplet–triplet annihilator (TTA) active 9,10-diphenylantracenes (DPA) and the related substituted variants in low concentrations were examined. A full experimental approach is presented for finding the necessary rate parameters with statistical standard deviation parameters. This was achieved by solving the pertinent non-analytical kinetic differential equation and fitting it to the experimental time-resolved photoluminescence of both slow fluorescence and sensitizer phosphorescence. The efficiency of the triplet–triplet energy transfer rate was found to be around 90% in THF but only around 75% in toluene. This appears to follow from the shorter lifetime of the sensitizer triplet in toluene. Moreover, the TTA transfer rate was on average more than 40% in THF toluene whereas a considerably lower value around 20–30% was found for toluene. This originated in an order of magnitude higher solvent quenching rate using toluene, based on the analysis of the delayed fluorescence decay traces. These are also higher than the statistically expected 1/9 TTA efficiency but in accordance with recent results in the literature, that attributed these high values to an inverse intersystem crossing process. In addition, quantum chemical calculations were carried out to reveal the pertinent excited triplet molecular orbitals of the lowest triplet excited state for a series of substituted DPAs, in comparison with the singlet ground state. Conclusively, these states distribute mainly in an anthracene ring in all compounds being in the range 1.64–1.65 eV above the ground state. The TTA efficiency was found to vary depending on the DPA annihilator substitution scheme and found to be smaller in THF. This is likely because the molecular framework over which the T1 excited molecular orbitals distribute is less sensitive for a longer lifetime of the annihilator triplet state. Full article

This research studied the recycling of borosilicate glass wastes from damaged laboratory glassware. The luminescent glasses were prepared by doping glass waste powder with rare earth ions, namely, dysprosium ions (Dy³⁺) and samarium ions (Sm³⁺), as well as co-doping with Dy³⁺ and Sm³⁺ at a concentration of 2% by weight. The sintering process was conducted in a microwave oven for a duration of 15 min. The photoluminescence spectra of the doped glasses were obtained under excitation at 401 nm and 388 nm. The results showed that the emission characteristics depended on the doping concentrations of Dy³⁺ and Sm³⁺ and the excitation wavelengths. Upon excitation at 401 nm, the co-doped glasses exhibited the maximum emission peak of Sm³⁺ at 601 nm (yellowish and orange region in the CIE chromaticity diagram) due to the energy transition from ⁴G_5/2 to ⁶H_7/2. When excited at 388 nm, however, the emission spectra of the co-doped glasses were similar to the characteristic emission peaks of Dy³⁺ (white region in the CIE chromaticity diagram), but the peak position exhibits a red shift. This could be attributed to an increase in the amount of non-bridging oxygens (NBOs) by co-doping. Full article

A series of AlGaN/GaN high-electron-mobility transistor (HEMT) structures, with an AlN thin buffer, GaN thick layer and Al_0.25Ga_0.75N layer (13–104 nm thick), is prepared by metal–organic chemical vapor deposition and investigated via multiple techniques. Spectroscopic ellipsometry (SE) and temperature-dependent measurements and penetrative analyses have achieved significant understanding of these HEMT structures. Bandgaps of AlGaN and GaN are acquired via SE-deduced relationships of refraction index n and extinguish coefficient k vs. wavelength λ in a simple but straightforward way. The optical constants of n and k, and the energy gap E_g of AlGaN layers, are found slightly altered with the variation in AlGaN layer thickness. The Urbach energy E_U at the AlGaN and GaN layers are deduced. High-resolution X-ray diffraction and calculations determined the extremely low screw dislocation density of 1.6 × 10⁸ cm⁻². The top AlGaN layer exhibits a tensile stress influenced by the under beneath GaN and its crystalline quality is improved with the increase in thickness. Comparative photoluminescence (PL) experiments using 266 nm and 325 nm two excitations reveal and confirm the 2DEG within the AlGaN-GaN HEMT structures. DUV (266 nm) excitation Raman scattering and calculations acquired carrier concentrations in compatible AlGaN and GaN layers. Full article