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Ligand induced anomalous emission shift of size-controlled CsPbBr <sub/>3</sub> nanocrystals
摘要： CsPbX3 perovskite nanocrystals (NCs) have attracted much attention from researchers because of their excellent photoelectric properties like high quantum yield, large absorption cross section, and simple preparation process. The addition of ligands in the synthesis process has a significant effect on the microstructure and photophysical properties of solution-processed NCs, which needs further extensive studies. In this Letter, the effects of ligand electronegativity on the size and photoluminescence (PL) properties of CsPbBr3 NCs were reported. One is typical oleic acid with weak electronegativity, and another is 2-acrylamide-2-methylpropionic sulfonic acid with strong electronegativity. The third is their typical mixture with a molar ratio of 1:1. With the increase in ligand electronegativity, the size of CsPbBr3 NCs increases significantly. However, in contrast to the traditional quantum size confinement effect, the PL peak exhibits an abnormal blue shift gradually and the ligand passivation effect on NC surface defects also becomes more significant. The physical mechanism of this anomalous PL shift phenomena of CsPbBr3 NCs was investigated using the time-resolved PL spectrum and transient absorption spectrum.
关键词： transient absorption spectrum,quantum size confinement,photoluminescence,CsPbX3 perovskite nanocrystals,ligand electronegativity,time-resolved PL spectrum
更新于2025-09-16 10:30:52
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Single Component Self-Assembled Thermally Activated Delayed Fluorescence Nanoprobe
摘要： A novel versatile thermally activated delayed fluorescence (TADF) nanoprobe, AI-Cz-NP, was designed and fabricated through self-assembly of the single-component amphiphilic monomer for potential applications in confocal imaging and time-resolved fluorescence imaging.
关键词： nanoprobe,self-assembly,thermally activated delayed fluorescence,confocal imaging,time-resolved fluorescence imaging
更新于2025-09-16 10:30:52
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Upgrade of laser pump time-resolved X-ray probes in Beijing synchrotron
摘要： The upgrade of the laser pump time-resolved X-ray probes, namely time-resolved X-ray absorption spectroscopy (TR-XAS) and X-ray diffraction (TR-XRD), implemented at the Beijing Synchrotron Radiation Facility, is described. The improvements include a superbunch fill, a high-efficiency fluorescence collection, an efficient spatial overlap protocol and a new data-acquisition scheme. After upgrade, the adequate TR-XAS signal is now obtained in a 0.3 mM solution, compared with a 6 mM solution in our previous report. Furthermore, to extend application in photophysics, the TR-XAS probe is applied on SrCoO2.5 thin film. And for the first time, TR-XAS is combined with TR-XRD to simultaneously detect the kinetic trace of structural changes in thin film.
关键词： time-resolved X-ray diffraction,time-resolved X-ray absorption spectroscopy,thin films,laser pump/X-ray probe
更新于2025-09-12 10:27:22
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Nanosecond electron holography by interference gating
摘要： The interference gating is a novel method for robust time-resolved electron holographic measurements by directly switching the interference. Here, a new arrangement is presented in which a biprism in the condenser aperture as a fast electric phase shifter is used to control the interference pattern. High-frequency stimulation of the electric phase shifter in the gigahertz range are performed and observed via electron holography, proving the feasibility of interference gating in the upper picosecond range. Despite the bandwidth limitation of 180 MHz of the current signal generator, a time resolution of 100 ns is achieved through forward correction of the control signal. With this time resolution, it is already possible to measure the transient response of the biasing holder system. Our method paves the way towards a closer look on fast dynamic processes with high temporal and spatial resolution.
关键词： Interference gating,Time-resolved electron holography,Nanosecond time resolution,Condenser biprism,Electrical biasing
更新于2025-09-12 10:27:22
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Photodetector Based on Spontaneously Grown Strongly Coupled MAPbBr3/N-rGO Hybrids Showing an Enhanced Performance
摘要： Recently, metal-halide perovskites have emerged as a candidate for optoelectronic applications such as photodetectors. However, the poor device performance and instability have limited their future commercialization. We herein report the spontaneous growth of perovskite/N-rGO hybrid structures using a facile solution method and their application for photodetectors. In the hybrid structures, perovskites were homogeneously wrapped by N-rGO sheets through strong hydrogen bonding. The strongly coupled N-rGOs facilitate the charge carrier transportation across the perovskite crystals, but also distort the surface lattice of the perovskite creating potential barrier for charge transfer. We optimize the addition of N-rGO in the hybrid structures to balance the interfacial structural distortion and the inter-crystal conductivity. A high-performance photodetection up to 3 × 104 A/W, external quantum efficiency (EQE) exceeding 105 % and detectivity up to 1012 Jones were achieved in the optimal device with the weight ratio between perovskites and N-rGO to be 8:1.5. The underlying mechanism behind the optimal N-rGO addition ratio in the hybrids has also been rationalized via time-resolved spectroscopic studies as a reference for future application.
关键词： hydrogen bonding,perovskite/N-rGO,hybrid material,photodetector,time-resolved spectroscopy
更新于2025-09-12 10:27:22
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Electric‐Withdrawing Anchor Group of Sensitizer for Dye‐Sensitized Solar Cells, Cyanoacrylic Acid or Benzoic Acid?
摘要： High electron injection efficiency is important for further development of dye-sensitized solar cells (DSSCs). Different electron acceptors have different electron injection capabilities, which affect device performance. Here, this article report on the effects of two organic triazatruxene (TAT)-based donor-π-bridge-acceptor sensitizers applied in DSSCs. The sensitizers had either rigid 4-ethynyl benzoic acid (EBA) or Z-type cyanoacrylic acid (CA) as their electron acceptor, denoted as ZL003 and ZL005, respectively. Time-resolved photoluminescence (TR-PL) spectroscopy was applied to reveal the electron transfer dynamics between the sensitizers and TiO2 films. Notably, ZL003 had higher electron injection efficiency compared with that of ZL005, which was consistent with the higher efficiency and photocurrent of devices based on the former. The dye loading of ZL003 was nearly twice as great as that of ZL005, which accounts for the lower photocurrent of the device. The charge recombination lifetimes for the two dyes were consistent with their open-circuit voltage. Consequently, the ZL003 based devices achieved a higher power conversion efficiency of 13.4% compared with only 7.2% for ZL005.
关键词： electron injection efficiency,time-resolved photoluminescence (TR-PL),dye-sensitized solar cells,electron acceptor
更新于2025-09-12 10:27:22
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Pico- to nanosecond pulsed laser-induced forward transfer (LIFT) of silver nanoparticle inks: a comparative study
摘要： Silver nanoparticle inks are among the key functional materials used in printed electronics. Depositing it by laser-induced forward transfer remains a challenging task because the non-linear rheological nature of these inks narrows the range of the laser processing parameters. Understanding, therefore, the influence of the laser parameters on the ejection dynamics and deposition quality is of critical importance. The influence of the laser pulse duration from pico- to nanosecond-laser-induced jet dynamics was investigated using time-resolved shadowgraphy imaging. Jet speed and surface area analyses showed that in the lower laser fluence level range, picosecond pulses induce higher surface area ejections which propagate at higher velocities. As the laser fluence levels were increased, the difference in jet velocity and surface area evolutions narrows. Deposition analysis showed a similar behavior with lower transfer thresholds and larger depositions at lower fluence range when picosecond-laser pulses were used.
关键词： Time-resolved shadowgraphy,Silver nanoparticle inks,Nanosecond pulses,Laser-induced forward transfer,Printed electronics,Picosecond pulses
更新于2025-09-12 10:27:22
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Internal quantum efficiencies of AlGaN quantum dots grown by molecular beam epitaxy and emitting in the UVA to UVC ranges
摘要： AlyGa1?yN quantum dots (QDs) have been grown by molecular beam epitaxy on AlxGa1?xN (0001) using a 2-dimensional–3-dimensional growth mode transition that leads to the formation of QDs. QDs have been grown for Al compositions y varying between 10% and 40%. The influence of the active region design [composition y, QD height, and bandgap difference (ΔEg) between the AlxGa1?xN cladding layer and the AlyGa1?yN QDs] is discussed based on microscopy, continuous wave photoluminescence (PL), and time-resolved PL (TRPL) measurements. In particular, increasing y leads to a shift of the QD emission toward shorter wavelengths, allowing covering a spectral range in the UV from 332 nm (UVA) to 276 nm (UVC) at room temperature (RT). The low-temperature (LT) internal quantum efficiency of the QD ensembles was estimated from TRPL experiments at 8 K and values between 11% and 66% were deduced. The highest internal quantum efficiency (IQE)-LT is found for the QDs with higher Al content y. Then, the PL spectrally integrated intensity ratios between RT and LT were measured to estimate the IQE of the samples at RT. The PL ratio is higher for larger ΔEg, for QDs with y of 0.1 or 0.2, and high PL intensity ratios up to 30% were also measured for QDs with larger y of 0.3 and 0.4. RT IQE values between 5% and 20% are deduced for AlyGa1?yN QDs emitting in the 276–308 nm range.
关键词： AlGaN,internal quantum efficiency,UVC,quantum dots,molecular beam epitaxy,time-resolved photoluminescence,photoluminescence,UVA
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE Research and Applications of Photonics in Defense Conference (RAPID) - Miramar Beach, FL, USA (2019.8.19-2019.8.21)] 2019 IEEE Research and Applications of Photonics in Defense Conference (RAPID) - Laser Diagnostics for Solid Rocket Propellants and Explosives
摘要： Laser diagnostics are essential for time-resolved studies of solid rocket propellant combustion and small explosive detonations. Digital in-line holography (DIH) is a powerful tool for three-dimensional particle tracking in multiphase flows. By combining DIH with complementary diagnostics, particle temperatures and soot/smoke properties can be identified.
关键词： digital in-line holography,solid rocket propellants,imaging pyrometry,explosives,phase-conjugate digital in-line holography,time-resolved laser-induced incandescence
更新于2025-09-12 10:27:22
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revealed by time-resolved photoluminescence spectroscopy
摘要： We systematically investigate the recombination mechanism of photogenerated charge carriers in bulk CsPbBr3 by means of time-resolved photoluminescence (TR-PL) spectroscopy at low temperature and various laser excitation powers. A dynamic recombination model is proposed to describe the TR-PL that predicts the time-dependent exciton and free-charge populations. It provides a clear representation of competing mono- and bimolecular recombination processes. A decrease in carrier lifetime with increasing laser intensity was observed that was attributed to exciton-exciton scattering. A bimolecular recombination coef?cient of ～10?7 cm3/s was obtained for exciton recombination. As the concentration of photoexcited carriers increases, stronger exciton-exciton annihilation occurs. The exciton-exciton annihilation rate for CsPbBr3 is 3.63 × 10?7 cm3 s?1 at 10-mW laser power. Notably, the exciton-exciton annihilation rate in bulk material is comparable to that obtained for photoexcited CsPbBr3 nanoscale quantum dots.
关键词： carrier recombination,bimolecular recombination,exciton-exciton annihilation,time-resolved photoluminescence,CsPbBr3
更新于2025-09-12 10:27:22