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Van der Waals heterostructures built by vertically stacked transition metal dichalcogenides (TMDs) exhibit a rich energy landscape, including interlayer and intervalley excitons. Recent experiments demonstrated an ultrafast charge transfer in TMD heterostructures. However, the nature of the charge transfer process has remained elusive. Based on a microscopic and material‐realistic exciton theory, we reveal that phonon‐mediated scattering via strongly hybridized intervalley excitons governs the charge transfer process that occurs on a sub‐100fs timescale. We track the time‐, momentum‐, and energy‐resolved relaxation dynamics of optically excited excitons and determine the temperature‐ and stacking‐dependent charge transfer time for different TMD bilayers. The provided insights present a major step in microscopic understanding of the technologically important charge transfer process in van der Waals heterostructures. Key Points Microscopic and fully quantum‐mechanic model is developed to calculate exciton dynamics in van der Waals heterostructures Charge transfer occurs on a femtosecond timescale and is a phonon‐mediated two‐step process Strongly hybridized dark exciton states play a crucial role for the charge transfer

The formation of chemical bonds between metal ions and their supports is an effective strategy to achieve good catalytic activity. However, both the synthesis of active metal species on a support and control of their coordination environment are still challenging. Here, we show the use of an organic compound to produce tubular carbon nitride (TCN) as a support for Pd nanoparticles (NPs), creating a composite material (NP-Pd-TCN). It was found that Pd ions preferentially bind with the electron-rich N atoms of TCN, leading to strong metal-support interactions that benefit charge transfer from g-C 3 N 4 to Pd. X-ray absorption spectroscopy further revealed that the metal-support interactions resulted in the formation of Pd-N bonds, which are responsible for the improvement in the charge dynamics as evidenced by the results from various techniques including photoluminescence (PL) spectroscopy, photocurrent measurements, and electrochemical impedance spectroscopy (EIS). Owing to the good dynamical properties, NP-Pd-TCN was used for photocatalytic hydrogen evolution under visible-light irradiation ( λ > 420 nm) and an excellent evolution rate of ∼ 381 µmol·h −1 (0.02 g of the photocatalyst) was attained. This work aims to promote a strategy to synthesize efficient photocatalysts for hydrogen production by controllably introducing metal nanoparticles on a support and in the meantime forming chemical bonds to achieve intimate metal-support contact.

The solar-driven reduction of CO 2 into valuable products is a promising method to alleviate global environmental problems and energy crises. However, the low surface charge density limits the photocatalytic conversion performance of CO 2 . Herein, a polymeric carbon nitride (PCN) photocatalyst with Zn single atoms (Zn 1 /CN) was designed and synthesized for CO 2 photoreduction. The results of the CO 2 photoreduction studies show that the CO and CH 4 yields of Zn 1 /CN increased fivefold, reaching 76.9 and 22.9 µmol/(g·h), respectively, in contrast to the unmodified PCN. Ar + plasma-etched X-ray photoelectron spectroscopy and synchrotron radiation-based X-ray absorption fine structure results reveal that Zn single atom is mainly present in the interlayer space of PCN in the Zn–N 4 configuration. Photoelectrochemical characterizations indicate that the interlayer Zn–N 4 configuration can amplify light absorption and establish an interlayer charge transfer channel. Light-assisted Kelvin probe force microscopy confirms that more photogenerated electrons are delivered to the catalyst surface through interlayer Zn–N 4 configuration, which increases its surface charge density. Further, in-situ infrared spectroscopy combined with density functional theory calculation reveals that promoted surface charge density accelerates key intermediates (⋆COOH) conversion, thus achieving efficient CO 2 conversion. This work elucidates the role of internal single atoms in catalytic surface reactions, which provides important implications for the design of single-atom catalysts.

Highlights A novel approach, precursor seed layer engineering, is applied to prepare Cu 2 ZnSnS 4 (CZTS) light-absorbing films using the solution-processed spin-coating method. Mo/CZTS/CdS/TiO 2 /Pt photocathode effectively mitigates defects in CZTS light absorber and the CZTS/CdS heterojunction interface, optimizing charge carrier dynamics. Record photoelectrochemical performance including half-cell solar-to-hydrogen (HC-STH) efficiency of 9.91%, photocurrent density of 29.44 mA cm −2 at 0 V RHE in 0.5 M H 2 SO 4 electrolyte, and STH efficiency of 2.20% in CZTS-BiVO 4 tandem cell in natural seawater is achieved. Despite being an excellent candidate for a photocathode, Cu 2 ZnSnS 4 (CZTS) performance is limited by suboptimal bulk and interfacial charge carrier dynamics. In this work, we introduce a facile and versatile CZTS precursor seed layer engineering technique, which significantly enhances crystal growth and mitigates detrimental defects in the post-sulfurized CZTS light-absorbing films. This effective optimization of defects and charge carrier dynamics results in a highly efficient CZTS/CdS/TiO 2 /Pt thin-film photocathode, achieving a record half-cell solar-to-hydrogen (HC-STH) conversion efficiency of 9.91%. Additionally, the photocathode exhibits a highest photocurrent density ( J ph ) of 29.44 mA cm −2 (at 0 V RHE ) and favorable onset potential ( V on ) of 0.73 V RHE . Furthermore, our CTZS photocathode demonstrates a remarkable J ph of 16.54 mA cm −2 and HC-STH efficiency of 2.56% in natural seawater, followed by an impressive unbiased STH efficiency of 2.20% in a CZTS-BiVO 4 tandem cell. The scalability of this approach is underscored by the successful fabrication of a 4 × 4 cm 2 module, highlighting its significant potential for practical, unbiased in situ solar seawater splitting applications.

The coupling of semiconductor (SC) and transition metal oxyhydroxide (TMOOH) is a promising approach for solar fuel production. However, the inevitable interfacial charge recombination and sluggish oxygen evolution reactions severely hinder the application of photoelectrochemical (PEC) device. This study demonstrates an innovative charge polarization strategy that simultaneously enhances both long‐range charge transfer and surface catalytic reaction dynamics through the rational construction of CoOx/MnOx heterointerface in SC/TMOOH system. Kelvin probe force microscopy, in situ ultraviolet/visible spectroelectrochemistry, and density functional theory calculations indicate that the tunable charge polarization of Coδ− and Mnδ+ can affect influences the SC/TMOOH and TMOOH/electrolyte interfaces, primarily through inducing the accelerated charge transfer dynamics (Kh) and diminishing the adsorption of oxygen‐containing intermediates. As anticipated, the BiVO4/CoOx/MnOx/FeNiOOH exhibits an impressive photocurrent of 6.75 mA cm−2 at 1.23 VRHE, along with a superior photostability. Furthermore, the smart approach can also be harnessed in the BiVO4/CoOx/CeOx/FeNiOOH photoanode. This study provides a novel polarization strategy for the design of optimal photoanodes for PEC water splitting. This research presents a charge polarization approach aimed at enhancing both long‐range charge transfer and surface catalytic activities by incorporating a CoOx/MnOx heterointerface within the semiconductor/transition metal oxyhydroxide system. As anticipated, the BiVO4/CoOx/MnOx/FeNiOOH exhibits an impressive photocurrent of 6.75 mA cm−2 at 1.23 VRHE, along with a superior photostability.

Context The development of efficient solar energy conversion technologies is crucial for addressing global energy challenges and reducing reliance on fossil fuels. Platinum(II) complexes are promising materials for photovoltaic applications due to their strong light absorption and long-lived excited states. However, their narrow absorption in the visible spectrum and stability issues limit their performance. Combining platinum(II) complexes with graphene quantum dots (GQDs) can enhance photovoltaic performance by leveraging the complementary light harvesting and charge transfer characteristics of the two components. This study utilizes density functional theory (DFT) calculations to explore their electronic structures, charge transfer dynamics, and photoelectric performance. Specifically, it investigates the effects of incorporating different substituents, either electron-donating or electron-withdrawing, onto the fluorene motif of the Pt(II) complex. The findings reveal that combining GQDs with Pt(II) complexes extends light absorption into the UV range, enabling comprehensive solar utilization. Upon photoexcitation, electrons migrate between the GQD conduction band and the Pt(II) complex, stabilizing charges and enhancing extraction. Substituents significantly influence charge transfer dynamics: electron-withdrawing groups promote transfer to the GQD, while electron-donating groups encourage charge separation and delocalization. Nanocomposites featuring electron-donating substituents achieve the highest energy conversion efficiencies, with GQD@Pt(II)-NPh2 reaching 24.6%. This is attributed to improved light harvesting, efficient charge injection, and reduced recombination. These insights guide the rational design of GQD-Pt(II) nanocomposites, optimizing charge separation and transfer processes for enhanced photovoltaic performance. The computational approach employed here provides a robust tool for developing advanced materials in renewable energy technologies. Methods The computational studies reported in this work were performed using the DFT approach, specifically employing the hybrid functional PBE0. The PBE0 functional’s accuracy in describing electronic structures and excited-state properties is essential for understanding charge transfer processes, photoabsorption, and emission characteristics in metal–organic complexes. Geometry optimizations and time-dependent DFT (TD-DFT) calculations were carried out to investigate the properties of the nanocomposites. The effects of solvents were replicated using the conductor-like polarizable continuum model (CPCM). The charge transfer length (ΔL) and interfragment charge transfer (ΔQ) were calculated using the Multiwfn software package, and all calculations were performed using the BDF software package.

Understanding the ultrafast carrier dynamics at the p‐n heterojunctions is indispensable for designing efficient photocatalysts. In this work, we used element‐specific time‐resolved soft X‐ray absorption spectroscopy (tr‐XAS) to investigate the ultrafast carrier transfer dynamics in a layered CuO/TiO2 heterostructure. On monitoring the transient response at the oxygen K‐, Cu L3‐, and Ti L3‐edges, it revealed hole accumulation at the CuO valence band (VB) on the timescale of several nanoseconds, whereas the photoexcited electron undergoes several processes. We observed that soon after photoexcitation, the electrons from the TiO2 conduction band (CB) diffuses into the CuO CB within ∼150 ps. However, the diffused electrons drifted towards the TiO2 CB within ∼800 ps, as it is energetically aligned at lower position and exhibits large electron population. The electrons there stays for longer durations ∼3500 ps by getting trapped into the deep trap states. This spatial separation, driven by the internal electric field of the p‐n interface, significantly suppresses the electron‐hole recombination. Our findings demonstrate that a ∼2.8 nm CuO overlayer effectively stabilizes long‐lived charge carriers, providing a basis for the enhanced photocatalytic performance observed in these heterostructures. Schematic illustration of the carrier dynamics in the layered CuO∖TiO2 heterostructure.

The ZnO and CeO 2 nanostructures were prepared via a thermal decomposition process. The CeO 2 –ZnO nanocomposites with various CeO 2 quantities of 0–5 mol% characterized the structure, morphology, and optical characteristics using XRD, FT–IR, SEM, UV–Vis spectroscopy, and PL techniques. The phase fraction, lattice constants, and defects were determined by the calculation from the XRD result. The 5 mol% CeO 2 –added ZnO sample exhibits the highest polar surface. SEM analysis revealed the presence of ZnO nanorods and CeO 2 nanoparticles. The composites principally featured ZnO with the spontaneous incorporation of CeO 2 nanoparticles. The bandgap was modified as CeO 2 content, showing 3.37 eV for ZnO and 3.31 eV for 5 mol% CeO 2 incorporation. Photoluminescence (PL) analysis demonstrated the Zn, Ce, and O defects and transformation of zinc interstitial (Zn i ) to Zn regular site (Zn Zn ). The photocatalytic degradation of Methylene Blue (MB) under visible light irradiation exhibited a superior efficiency than the single catalyst, determining the influence of charge transfer between the composite interfaces in combination with the sublevel energy of both Ce 3+ and oxygen vacancy (V o ) being the center of electron trapping. This research points out the characteristics and the performance of thermal decomposition–processed CeO 2 –ZnO composites in the photo-induced technology. The charge transfers were discussed, associating with the structural constants, emissive spectra, and sublevel energy. Graphical abstract

Charge transfer properties between 3D and 2D perovskite layers play a key role in determining the performance of 3D/2D heterostructure perovskite solar cells (PSCs). However, the exact photophysical behaviors at 3D/2D perovskite heterostructure remain ambiguous, which makes it challenging to form the desired 3D/2D heterostructure. Herein, via combining the state‐of‐the‐art ultrafast spectroscopies of femtosecond transient absorption spectroscopy, transient absorption microscopy and time‐resolved photoluminescence spectroscopy, charge transfer and recombination dynamics are unveiled at 3D/2D perovskite heterostructure, for comparison, where the 2D layers are fabricated through the two distinct approaches of organic ligand surface reaction (2DL) and 2D crystal seed direct deposition (2DS), respectively. 3D/2DS heterostructure exhibits superior hole transfer from 3D to 2DS, featuring a large spatial diffusion constant and high charge mobility compared to 3D/2DL, attributed to the higher phase purity and the lower defects in 2DS. Moreover, 3D/2DS heterostructure yields suppressed nonradiative recombination, reduced Langevin recombination, and increased quasi‐Fermi level splitting, significantly aiding fast photoinduced charge transfer at such heterostructure. These advantages are further confirmed by a remarkably improved PSC efficiency using 3D/2DS, especially in terms of enhanced open‐circuit voltage and diminished energy loss. This work sheds light on the dynamics at 3D/2D heterostructures, providing a promising guideline for designing 3D/2D high‐performance PSCs. Charge transfer and recombination dynamics at 3D/2D perovskite heterostructure have been fully investigated via combined state‐of‐the‐art ultrafast spectroscopies, aiding to design of the desired 3D/2D perovskite heterostructure and thus push 3D/2D perovskite solar cell technology forward.

We study the role of electronic interface states on the electron transfer dynamics between layers of the organic semiconductor 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) and the (111) and (100) surfaces of silver. For this purpose, we investigate the change of the decay dynamics of the first (n = 1) image-potential state on these surfaces upon adsorption of an ordered monolayer of PTCDA by means of time-resolved two-photon photoemission (2PPE). We find that the already short lifetime of the (n = 1)-state on Ag(111) is only slightly further reduced by PTCDA adsorption, whereas a much stronger reduction by a factor of three is observed for adsorption on Ag(100) resulting in similar lifetimes for both orientations. We show by model calculations on the basis of an analytical one-dimensional pseudo-potential that the enhanced decay for PTCDA/Ag(100) can be attributed to the opening of an additional channel for electron-electron scattering by the formation of an interface state which is derived from the Shockley-type surface resonance of Ag(100).