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Synthesis of Cu2O/Carbon film/NiCoB-GO Heterostructure Photocathode for Efficient Photoelectrochemical Water Splitting
摘要： Photoelectrochemical (PEC) water splitting offers a promising way to convert solar energy to chemical energy. The electron transfer rate and surface-catalyzed ability toward hydrogen evolution reaction (HER) play the key roles in the efficiency of PEC water splitting. In this work, a Cu2O/Carbon film/NiCoB-GO heterostructure photocathode is fabricated. Among them, thickness-controllable carbon film served as the electron transport and protective layer with favourable optical property, NiCoB-GO amorphous catalyst displays the efficient performance towards HER in neutral condition. The optimized photocathode shows the PEC-HER performance with a photocurrent density of -2.9 mA/cm2 at 0 V vs. RHE, and it also presents better stability than bare Cu2O. This work provides a novel heterostructure photocathode for promoting solar-driven PEC water splitting efficiently.
关键词： Femtosecond transient absorption spectroscopy,Photoelectrochemical water splitting,Electron transport path,Carbon film,Amorphous catalyst
更新于2025-09-19 17:15:36
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A dominant factor of the cycloreversion reactivity of diarylethene derivatives as revealed by femtosecond time-resolved absorption spectroscopy
摘要： Dynamics of the cycloreversion reaction of a photochromic diarylethene derivative with a small ring-opening reaction yield (～1%) was investigated by using femtosecond transient absorption spectroscopy. The reaction rate constant and activation barrier on the reaction coordinate were quantitatively analyzed on the basis of the temperature and excitation wavelength dependencies of the reaction yield and excited state dynamics. From the comparison of the present results with those in a more reactive derivative, we concluded that a key factor regulating the overall reaction yield is the branching ratio at the conical intersection where the excited state population is split into the product and the initial reactant. The excitation wavelength dependence of the dynamics indicated that the geometrical relaxation and vibrational cooling proceed in a few picosecond time scale behind the cycloreversion process, and the vibrational excess energy assists the molecule to climb up the energy barrier.
关键词： vibrational cooling,diarylethene derivative,photochromic,femtosecond transient absorption spectroscopy,cycloreversion reaction
更新于2025-09-19 17:13:59
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Studying of photo-excitation dynamics and photodetector based on MoSe2 nanosheet
摘要： The photo-excitation dynamics occurring in the nanosheet of MoSe2 have been studied by employing the transient absorption. We find that four types of dynamic behaviors participate in the relaxation of excited MoSe2 nanosheet by global fitting, which corresponds to the exciton-exciton interaction, exciton capture by trapping state, exciton dissociation and free charge movement. Since many free charge has generated after photo-excitation, the photo-detector based on MoSe2 nanosheet is fabricated and the period- and voltage-dependent photocurrent is further clarified. In addition, nanosecond transient photocurrent test probes the dynamics of carrier and confirms that illumination intensity would accelerate the lifetime of carrier recombination to 1 μs at high intensity and enhance the corresponding loss of carrier. Moreover, it is also found that the bias voltage would linearly facilitate the yield of free carriers in photo-detector and the lifetime of carrier recombination would decrease to 4 μs at 60 V. The final results could help people to further understand the photo-physical property of MoSe2 nanosheet and facilitate its application in the opto-electronic devices.
关键词： Photo-excitation dynamics,MoSe2 nanosheet,Transient absorption,Photodetector
更新于2025-09-19 17:13:59
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High-performance perovskite solar cells based on passivating interfacial and intergranular defects
摘要： Planar-structure perovskite solar cells have attracted more and more attention, because their simple and low-temperature preparation processing. However, the performance of perovskite solar cells is currently limited by defect-induced recombination at interfaces between perovskite and charge transport layers. In this work, a filmy poly methyl methacrylate (PMMA) layer introduced in Perovskite/Spiro-OMeTAD interface to passivate the interfacial and interganular defects, by which a high open-circuit voltage (1.18 V) is acquired, and the optimal device shows a steady-state power conversion efficiency of 20.5% and negligible hysteresis. Femtosecond transient absorption measurement confirms a significant reduction in non-radiative recombination for passivated devices. Mott-Schottky measurement indicates improved flat band potential and carrier density in passivated devices, consisting with the increased voltage. In addition, PMMA film can protect perovskite film from moisture and oxygen erosion. The unsealed device still maintains 95% of the initial efficiency under ambient conditions with 60% relative humidity for one month. This approach solves one of the main limitations of interfacial recombination and shows its potential to improve the performance of perovskite solar cells in the future.
关键词： Transient absorption,PMMA,Passivation,Perovskite solar cells
更新于2025-09-19 17:13:59
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Photovoltaic activity of electrodes based on intact photosystem I electrodeposited on bare conducting glass
摘要： We demonstrate photovoltaic activity of electrodes composed of fluorine-doped tin oxide (FTO) conducting glass and a multilayer of trimeric photosystem I (PSI) from cyanobacterium Synechocystis sp. PCC 6803 yielding, at open circuit potential (OCP) of + 100 mV (vs. SHE), internal quantum efficiency of (0.37 ± 0.11)% and photocurrent density of up to (0.5 ± 0.1) μA/cm2. The photocurrent measured for OCP is of cathodic nature meaning that preferentially the electrons are injected from the conducting layer of the FTO glass to the photooxidized PSI primary electron donor, P700+, and further transferred from the photoreduced final electron acceptor of PSI, Fb, via ascorbate electrolyte to the counter electrode. This observation is consistent with preferential donor-side orientation of PSI on FTO imposed by applied electrodeposition. However, by applying high-positive bias (+ 620 mV) to the PSI-FTO electrode, exceeding redox midpoint potential of P700 (+ 450 mV), the photocurrent reverses its orientation and becomes anodic. This is explained by “switching off” the natural photoactivity of PSI particles (by the electrochemical oxidation of P700 to P700+) and “switching on” the anodic photocurrent from PSI antenna Chls prone to photooxidation at high potentials. The efficient control of the P700 redox state (P700 or P700+) by external bias applied to the PSI-FTO electrodes was evidenced by ultrafast transient absorption spectroscopy. The advantage of the presented system is its structural simplicity together with in situ-proven high intactness of the PSI particles.
关键词： Photoelectrochemical measurements,Cyanobacterium Synechocystis sp. PCC 6803,Femtosecond-transient absorption,Photovoltaics,FTO conducting glass,Photosystem I
更新于2025-09-19 17:13:59
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Extent of Shallow/Deep Trap States beyond the Conduction Band Minimum in Defect-Tolerant CsPbBr <sub/>3</sub> Perovskite Quantum Dot: Control over the Degree of Charge Carrier Recombination
摘要： Perovskite quantum dots (PQDs) are known to be defect tolerant possessing clean band-gap with optically inactive benign defect states. However, we show that there exists significant deep trap states beyond conduction band minimum, although the extent of shallow trap states is observed to be minimal. Extent of deep trap states beyond conduction band minimum seem to significant in PQD, however the extent is less than even optically robust CdSe and InP based core/alloy-shell QDs. In-depth analyses based on ultrafast transient absorption and ultrasensitive single particle spectroscopic investigations decode the underlying degree of charge carrier recombination in CsPbBr3 PQD which are quite important for energy applications.
关键词： Perovskite quantum dots,ultrafast transient absorption,defect tolerant,single particle spectroscopy,charge carrier recombination,trap states
更新于2025-09-19 17:13:59
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Photoswitching mechanism of a fluorescent protein revealed by time-resolved crystallography and transient absorption spectroscopy
摘要： Reversibly switchable fluorescent proteins (RSFPs) serve as markers in advanced fluorescence imaging. Photoswitching from a non-fluorescent off-state to a fluorescent on-state involves trans-to-cis chromophore isomerization and proton transfer. Whereas excited-state events on the ps timescale have been structurally characterized, conformational changes on slower timescales remain elusive. Here we describe the off-to-on photoswitching mechanism in the RSFP rsEGFP2 by using a combination of time-resolved serial crystallography at an X-ray free-electron laser and ns-resolved pump–probe UV-visible spectroscopy. Ten ns after photoexcitation, the crystal structure features a chromophore that isomerized from trans to cis but the surrounding pocket features conformational differences compared to the final on-state. Spectroscopy identifies the chromophore in this ground-state photo-intermediate as being protonated. Deprotonation then occurs on the μs timescale and correlates with a conformational change of the conserved neighbouring histidine. Together with a previous excited-state study, our data allow establishing a detailed mechanism of off-to-on photoswitching in rsEGFP2.
关键词： time-resolved crystallography,fluorescent proteins,transient absorption spectroscopy,photoswitching,rsEGFP2
更新于2025-09-19 17:13:59
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X-ray transient absorption spectroscopy by an ultrashort x-ray-laser pulse in a continuous-wave IR field
摘要： X-ray transient absorption spectra (XTAS) of molecules are theoretically investigated in a femtosecond x-ray pump and continuous-wave (cw) infrared (IR)-control scenario. The scheme is exemplified by a CO molecule resonantly pumped into carbon and oxygen core-excited 1s → π ? states by a weak femtosecond x-ray pulse, while dynamic Stark shifts are induced by the cw IR-control radiation. As a result, significant shoulder structures appear in XTAS showing strong dependence on the phase of IR radiation relative to the envelope of the x-ray pulse. Due to a significant difference in the frequencies of the two pulses, the present XTAS scheme provides much clear interpretation of the dynamic Stark effects as compared to the attosecond UV transient absorption scenario. Within the suggested two-level model, where the total spectrum is decomposed as incoherent superposition of contributions from different vibrational excitations weighted by the Franck-Condon Factors, all spectral structures can be well identified and interpreted in a good agreement with the full-scale molecular simulations. Well-characterized XTAS in the proposed IR-control scheme can be applied for fine phase synchronization between IR and x-ray pulses, highly demanded in modern experiments on x-ray free-electron lasers.
关键词： X-ray transient absorption spectroscopy,continuous-wave IR field,Franck-Condon Factors,dynamic Stark shifts,ultrashort x-ray-laser pulse
更新于2025-09-16 10:30:52
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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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Ultrafast Response of a Hybrid Device Based on Strongly Coupled Monolayer WS <sub/>2</sub> and Photonic Crystals: The Effect of Photoinduced Coulombic Screening
摘要： Quantum interactions between transition metal dichalcogenides (TMDs) and optical cavities are rapidly becoming an appealing research topic since these interactions underly a broad spectrum of optical phenomena. Here, we fabricate a simple device in which coherent strong coupling interactions occur between a photonic crystal (PhC) slab and monolayer tungsten disulfide (WS2). Both steady-state angle-resolved spectroscopy and transient absorption microscopy (TAM) are employed to explore the coupling behavior of this device. Specifically, anticrossing dispersions are observed in the hybrid device, indicating a Rabi splitting of 40.2 meV. A newly formed spectral feature emerges in the transient absorption (TA) spectrum of this polariton device under near-resonant excitation, which is subsequently evidenced to be a signature of the upper hybrid exciton–polariton state. Moreover, by carefully analyzing the ultrafast responses of both bare WS2 and the WS2-PhC polariton device excited both off resonance and near resonance, it is found that nonequilibrium thermal decay induces Coulombic screening in the monolayer WS2, which has a major impact on the formation of exciton–polariton. The results of this work could not only improve the current understanding of photophysics in the strong light–matter coupling regime but also lay the foundation for tailoring the development of TMD-based coherent devices.
关键词： strong coupling,transition metal dichalcogenides,photonic crystals,Rabi splitting,transient absorption microscopy,Coulombic screening
更新于2025-09-16 10:30:52