A Facet‐Dependent Schottky‐Junction Electron Shuttle in a BiVO4{010}–Au–Cu2O Z‐Scheme Photocatalyst for Efficient Charge Separation

Interfacial charge separation and transfer are the main challenges of efficient semiconductor‐based Z‐scheme photocatalytic systems. Here, it is discovered that a Schottky junction at the interface between the BiVO₄ {010} facet and Au is an efficient electron‐transfer route useful for constructing a high‐performance BiVO₄{010}–Au–Cu₂O Z‐scheme photocatalyst. Spectroscopic and computational studies reveal that hot electrons in BiVO₄ {010} more easily cross the Schottky barrier to expedite the migration from BiVO₄ {010} to Au and are subsequently captured by the excited holes in Cu₂O. This crystal‐facet‐dependent electron shuttle allows the long‐lived holes and electrons to stay in the valence band of BiVO₄ and conduction band of Cu₂O, respectively, contributing to improved light‐driven CO₂ reduction. This unique semiconductor crystal‐facet sandwich structure will provide an innovative strategy for rational design of advanced Z‐scheme photocatalysts.     

Enhanced Charge Separation Efficiency in DNA Templated Polymer Solar Cells

The insertion of a DNA nanolayer into polymer based solar cells, between the electron transport layer (ETL) and the active material, is proposed to improve the charge separation efficiency. Complete bulk heterojunction donor–acceptor solar cells of the layered type glass/electrode (indium tin oxide)/ETL/P3HT:PC₇₀BM/hole transport layer/electrode (Ag) are investigated using femtosecond transient absorption spectroscopy both in the NIR and the UV–vis regions of the spectrum. The transient spectral changes indicate that when the DNA is deposited on the ZnO nanoparticles (ZnO‐NPs) it can imprint a different long range order on the poly(3‐hexylthiophene) (P3HT) polymer with respect to the non‐ZnO‐NPs/DNA containing cells. This leads to a larger delocalization of the initially formed exciton and its faster quenching which is attributed to more efficient exciton dissociation. Finally, the temporal response of the NIR absorption shows that the DNA promotes more efficient production of charge transfer states and free polarons in the P3HT cation indicating that the increased exciton dissociation correlates with increased charge separation.     

A Solar Responsive Battery Based on Charge Separation and Redox Coupled Covalent Organic Framework

Solar-responsive battery holds great promise in solar-to-electrochemical energy storage, but is impeded by the lack of efficient photoelectrochemical-cathodes. Herein, a crystalline mesoporous (≈4.0 nm) covalent organic framework (TA-PT COF) with repeating units consisting of covalently linked triphenylamine (TPA) and perylenetetracarboxylic diimide (PTCDI) is presented. The repeating unit functions as both a donor–acceptor pair and a dual-redox site to realize a molecule-level coupling of intramolecular charge separation (τCS = 136.2 ps, τCR = 949 ps) and reversible redox chemistry (C=O/C O−, TPA/TPA+). Equipped with this photoelectrochemical cathode, a reversible aqueous solar-responsive battery delivered a reliable voltage-response of 376 mV, an extra round-trip efficiency of 35% and a good light durability (500 cycles). A photo-coupled electron/mass transfer mechanism of photoelectrons for Zn²⁺ storage and holes for OTf− storage is further revealed, shedding light on a new photoelectrochemical cathode design based on charge separation and redox-coupled COF for efficient solar-responsive batteries.     

Linking Group Influences Charge Separation and Recombination in All‐Conjugated Block Copolymer Photovoltaics

All‐conjugated block copolymers bring together hole‐ and electron‐conductive polymers and can be used as the active layer of solution‐processed photovoltaic devices, but it remains unclear how molecular structure, morphology, and electronic properties influence performance. Here, the role of the chemical linker is investigated through analysis of two donor–linker–acceptor block copolymers that differ in the chemistry of the linking group. Device studies show that power conversion efficiencies differ by a factor of 40 between the two polymers, and ultrafast transient absorption measurements reveal charge separation only in block copolymers that contain a wide bandgap monomer at the donor–acceptor interface. Optical measurements reveal the formation of a low‐energy excited state when donor and acceptor blocks are directly linked without this wide bandgap monomer. For both samples studied, it is found that the rate of charge recombination in these systems is faster than in poly­mer–polymer and polymer–fullerene blends. This work demonstrates that the linking group chemistry influences charge separation in all‐conjugated block copolymer systems, and further improvement of photovoltaic performance may be possible through optimization of the linking group. These results also suggest that all‐conjugated block copolymers can be used as model systems for the donor–acceptor interface in bulk heterojunction blends.     

A Review of MOFs and Their Composites-Based Photocatalysts: Synthesis and Applications

Photocatalysis is considered to be a green and environment-friendly technology since it can convert solar energy into other types of chemical energies. Over the past several years, metal-organic frameworks (MOFs)-based photocatalysts have received remarkable research interest due to their unique morphology, high photocatalytic performance, good chemical stability, easy synthesis, and low cost. In this review, the synthetic strategies of developing MOFs-based photocatalysts are first introduced. Second, the recent progress in the fabrication of various types of MOFs composites photocatalysts is summarized. Third, the different applications including hydrogen evolution reaction, oxygen evolution reaction, overall water splitting, nitrogen reduction reaction, carbon dioxide reduction reaction as well as photodegradation of organic pollutants of MOFs-based photocatalysts are summed up. Finally, the challenges and some suggestions for the future development of MOFs- and their composites-based photocatalysts are also highlighted. It is expected that this report will help researchers to systematically devise and develop highly efficient photocatalysts based on MOFs and their composites.     

Quantification of Temperature-Dependent Charge Separation and Recombination Dynamics in Non-Fullerene Organic Photovoltaics

Transient optical spectroscopy is used to quantify the temperature-dependence of charge separation and recombination dynamics in P3TEA:SF-PDI₂ and PM6:Y6, two non-fullerene organic photovoltaic (OPV) systems with a negligible driving force and high photocurrent quantum yields. By tracking the intensity of the transient electroabsorption response that arises upon interfacial charge separation in P3TEA:SF-PDI₂, a free charge generation rate constant of ≈2.4 × 10¹⁰ s⁻¹ is observed at room temperature, with an average energy of ≈230 meV stored between the interfacial charge pairs. Thermally activated charge separation is also observed in PM6:Y6, and a faster charge separation rate of ≈5.5 × 10¹⁰ s⁻¹ is estimated at room temperature, which is consistent with the higher device efficiency. When both blends are cooled down to cryogenic temperature, the reduced charge separation rate leads to increasing charge recombination either directly at the donor-acceptor interface or via the emissive singlet exciton state. A kinetic model is used to rationalize the results, showing that although photogenerated charges have to overcome a significant Coulomb potential to generate free carriers, OPV blends can achieve high photocurrent generation yields given that the thermal dissociation rate of charges outcompetes the recombination rate.     

Nature and Role of Surface Junctions in BiOIO3 Photocatalysts

BiOIO₃ photocatalysts exposing (010) and (100) surfaces show high efficiency in photocatalytic experiments thanks to an efficient charge separation: photogenerated electrons migrate to the (010) face, and holes move to the (100) one (F. Chen, et al.). However, if one considers the band alignment of the two thermodynamically most stable terminations of the (010) and (100) surfaces as derived from high-level density functional theory calculations, the band alignment is opposite to the experiment even if the formation of an explicit (010)/(100) junction is considered. To reconcile theory with experiment, one has to invoke the formation of a junction between a less stable (010) surface termination with the most stable (100) one. New chemical bonds at the interface result in a thermodynamically stable system and a significant charge transfer. This junction not only provides the correct band alignment, but also a position of the energy levels that is fully consistent with the experiment. This shows that in order to rationalize the behavior of semiconducting materials where charge separation helps the photoactivity, one has to describe the formation of explicit interfaces with atomistic precision, and to take into account the overall thermodynamic stability of the system.     

Critical Aspects and Recent Advances in Structural Engineering of Photocatalysts for Sunlight‐Driven Photocatalytic Reduction of CO2 into Fuels

The catalytic conversion of CO₂ into valuable fuels is a compelling solution for tackling the global warming and fuel crisis. Light absorption and charge separation, as well as adsorption/activation of CO₂ on the photocatalyst surface, are essential steps for this process. This article reviews the CO₂ photoreduction mechanisms and critical aspects that greatly affect the photoreduction efficiency. Additionally, different materials for CO₂ photoreduction are provided, including d⁰ and d¹⁰ metal oxides/mixed oxides, sulfides, polymeric materials, and metal phosphides with visible response, metal‐organic frameworks, and layer double hydroxides. Furthermore, various structural engineering strategies and corresponding state‐of‐the‐art photocatalytic systems are reviewed and discussed, such as bandgap engineering, geometrical nanostructure engineering, and heterostructure engineering. Each strategy has advantages and disadvantages, requiring further adjustment to further improve the photocatalytic performance of the photocatalyst. Based on this review, it is greatly expected that efficiently artificial systems and the breakthrough technologies for CO₂ reduction will be successfully developed in the future to solve the energy shortage as well as the environmental problem.     

Modulating Charge Separation Efficiency of Water Oxidation Photoanodes with Polyelectrolyte‐Assembled Interfacial Dipole Layers

The charge separation efficiency of water oxidation photoanodes is modulated by depositing polyelectrolyte multilayers on their surface using layer‐by‐layer (LbL) assembly. The deposition of the polyelectrolyte multilayers of cationic poly(diallyldimethylammonium chloride) and anionic poly(styrene sulfonate) induces the formation of interfacial dipole layers on the surface of Fe₂O₃ and TiO₂ photoanodes. The charge separation efficiency is modulated by tuning their magnitude and direction, which in turn can be achieved by controlling the number of bilayers and type of terminal polyelectrolytes, respectively. Specifically, the multilayers terminated with anionic poly(styrene sulfonate) exhibit a higher charge separation efficiency than those with cationic counterparts. Furthermore, the deposition of water oxidation molecular catalysts on top of interfacial dipole layers enables more efficient photoelectrochemical water oxidation. The approach exploiting the polyelectrolyte multilayers for improving the charge separation efficiency is effective regardless of pH and types of photoelectrodes. Considering the versatility of the LbL assembly, it is anticipated that this study will provide insights for the design and fabrication of efficient photoelectrodes.     

Photocatalyst Interface Engineering: Spatially Confined Growth of ZnFe2O4 within Graphene Networks as Excellent Visible‐Light‐Driven Photocatalysts

High‐performance photocatalysts should have highly crystallized nanocrystals (NCs) with small sizes, high separation efficiency of photogenerated electron–hole pairs, fast transport and consumption of photon‐excited electrons from the surface of catalyst, high adsorption of organic pollutant, and suitable band gap for maximally utilizing sunlight energy. However, the design and synthesis of these versatile structures still remain a big challenge. Here, we report a novel strategy for the synthesis of ultrasmall and highly crystallized graphene–ZnFe₂O₄ photocatalyst through interface engineering by using interconnected graphene network as barrier for spatially confined growth of ZnFe₂O₄, as transport channels for photon‐excited electron from the surface of catalyst, as well as the electron reservoir for suppressing the recombination of photogenerated electron–hole pairs. As a result, about 20 nm ZnFe₂O₄ NCs with highly crystallized (311) plane confined in the graphene network exhibit an excellent visible‐light‐driven photocatalytic activity with an ultrafast degradation rate of 1.924 × 10^?7 mol g^?1 s^?1 for methylene blue, much higher than those of previously reported photocatalysts such as spinel‐based photocatalysts (20 times), TiO₂‐based photocatalysts (4 times), and other photocatalysts (4 times). Our strategy can be further extended to fabricate other catalysts and electrode materials for supercapacitors and Li‐ion batteries.     

Enhanced Water‐Splitting Performance of Perovskite SrTaO2N Photoanode Film through Ameliorating Interparticle Charge Transport

Here SrTaO₂N has been found to exhibit photoelectrochemical water splitting, with a theoretical solar‐to‐hydrogen efficiency of 14.4%. Ameliorating the interparticle charge transport by H₂ annealing, the solar photocurrent of the SrTaO₂N(H) granular film at 1.23 V versus reversible hydrogen electrode (RHE) is increased by ≈250% in comparison with the SrTaO₂N film. Using an aberration corrected scanning transmission electron microscope and super‐X energy dispersive spectroscopy, the atomic scale observation has proved a decrease of oxygen concentrations in the surface of SrTaO₂N(H) particle, which may allow its electrical conductivity to be increased from 0.77 × 10^?6 to 2.65 × 10^?6 S cm^?1 and therefore the charge separation efficiency has been greatly increased by ≈330%. After being modified by Co–Pi water oxidation catalyst, the SrTaO₂N(H) photoanode shows a solar photocurrent of 1.1 mA cm^?2 and an incident photo‐to‐current efficiency value of ≈20% at 400–460 nm and 1.23 V versus RHE, which suggests that it is a new promising photoanode material for solar water splitting.     

半球陀螺谐振子的金属化镀膜工艺技术研究

高品质因数(即高Q值,Q>107)的石英半球谐振子是制造高精度半球谐振陀螺的关键,而球面金属化镀膜工艺是半球振子制造的重要工艺环节。该文介绍了金属化镀膜工艺及其膜层均匀性对谐振子品质因数的影响及降低膜层残余应力的工艺解决方案等。     

光电导聚合物中空间电荷光栅形成过程的研究

本文研究了光电导聚合物中空间电荷场的建立过程和稳态特性。研究了电荷俘获中心对空间电荷场强度，建立时间以及相移的影响。     

磁控管中的空间电荷效应研究

对磁控管中由于外加磁场存在而导致的空间电荷效应进行了研究.通过求解正交场中的粒子运动方程,给出了阴极表面电位分布与外加磁场和阴极发射电流的关系,并指出磁控管中合适的发射电流是其最佳工作的前提.通过全电磁粒子仿真和实验测试证实了该效应对磁控管工作性能的影响,为高效率低噪声磁控管的研究提供了新思路.     

An Improved Charge Pumping Method to Study Distribution of Trapped Charges in SONOS Memory

In silicon-oxide-nitride-oxide-silicon (SONOS) memory and other charge trapping memories,the charge distribution after programming operation has great impact on the device’s characteristics,such as reading,programming/erasing,and reliability.The lateral distribution of injected charges can be measured precisely using the charge pumping method.To improve the precision of the actual measurement,a combination of a constant low voltage method and a constant high voltage method is introduced during the charge pumping testing of the drain side and the source side,respectively.Finally,the electron distribution after channel hot electron programming in SONOS memory is obtained,which is close to the drain side with a width of about 50nm.     

Monodisperse Metallic NiCoSe2 Hollow Sub‐Microspheres: Formation Process,Intrinsic Charge‐Storage Mechanism,and Appealing Pseudocapacitance as Highly Conductive Electrode for Electrochemical Supercapacitors

Highly conductive metal selenides are gaining prominence as promising electrode materials in electrochemical energy‐storage fields. However, phase‐pure bimetallic selenides are scarcely retrieved, and their underlying charge‐storage mechanisms are still far from clear. Here, first a solvothermal strategy is devised to purposefully fabricate monodisperse hollow NiCoSe₂ (H‐NiCoSe₂) sub‐microspheres. Inherent formation of metallic H‐NiCoSe₂ is tentatively put forward with comparative structure‐evolution investigations. Interestingly, the fresh H‐NiCoSe₂ does not demonstrate striking supercapacitive behaviors when evaluated for electrochemical supercapacitors (ESs). But it exhibits competitive pseudocapacitance of ≈750 F g^?1 at a rate of 3 A g^?1 with a high loading of 7 mg cm^?2 after ≈100 cyclic voltammetry (CV) cycles. With systematic physicochemical/electrochemical analyses, intrinsic energy‐storage mechanism of the H‐NiCoSe₂ is convincingly revealed that the electrooxidation‐generated biactive CoOOH/NiOOH phases in aqueous KOH over CV scanning, rather than the H‐NiCoSe₂ itself, account for the remarkable pesudocapacitance observed after cycling. An assembled H‐NiCoSe₂‐based asymmetric device has delivered an energy density of ≈25.5 Wh kg^?1 with a power rate of ≈3.75 kW kg^?1, and long‐span cycle life. More significantly, the electrode design and new perspectives here hold profound promise in enriching material synthesis methodologies and in‐depth understanding of the complex charge‐storage process of newly emerging pseudocapacitive materials for next‐generation ESs.