Search

The chiral light field has attracted great attention owing to its interaction with chiral matter. The generation of chiral light fields with rich structures has become crucial as it can expand application scenarios. Herein, we introduce a chiral optical vortex lattice. As a whole, the optical vortex lattice has a chiral intensity distribution, with each spiral arm having sub-vortices (chiral phase). By using an expansion factor to adjust the involute of a circular lattice, this helical optical vortex lattice can be continuously varied from a circular lattice. The chirality of intensity and phase can be controlled independently. Furthermore, the optical tweezers using the lattice demonstrate the capability of sub-vortices to manipulate particle movement, with the chiral intensity determining the trajectory of particle motion. As the lattice possesses both intensity and phase chirality, it may also find potential applications in tasks such as chiral structure microfabrication. [ABSTRACT FROM AUTHOR]

Nanocrystalline Cu2Cu1−xFexSnS4 (CCFTS) was prepared by a simple liquid-phase method. Physiochemical properties of the CCFTS powder as well as the CEs fabricated thereby were investigated using XRD, Raman spectroscopy, SEM, UV–Vis absorption, electrochemical impedance spectroscopy (EIS), etc. Conduction band shifts as well as the bandgap increases in the as-prepared CCFTS as a function of the Fe content were observed. For the dye-sensitized solar cells (DSSCs) with CCFTS counter electrodes (CEs), charge transfer impedance (Rct1) and short-circuit current (Jsc) were reduced by 64.54% and improved by 14.64%, respectively, compared with that with Fe-free Cu3SnS4 (CTS) CE. The enhancement of electron transfer through the CE/electrolyte interfaces stems from the optimal energy level alignment and the surface morphology tuned by the Fe alloying and hence improve the electrocatalytic activity of the CEs for the reduction from I3− to I−. As a consequence, photovoltaic conversion efficiency (PCE) of 6.95% was obtained which is 1.25 times that of the cell with Fe-free CTS CE. This work confirmed that element alloying into nanocrystalline transition metal compounds is effective for catalytic activity improvement. Material preparation reported herein is feasible, has high efficiency and low cost, and believed beneficial to high DSSCs development. [ABSTRACT FROM AUTHOR]

Unique wool-ball shaped nanocrystalline CoS was synthesized using solvothermal method in which dopamine (DA) was added as carbon source to combine with the CoS. The DA in situ polymerized and coated on the CoS particle surfaces during the solvothermal process. N, S co-doped carbon-encapsulated CoS(Co9S8) were achieved after a post carbonization. In the composites, CoS(Co9S8) nanocrystals and carbon are tightly bound and embedded into the amorphous carbon layer to form a spherical core–shell structure. Hybrid counter electrodes (CEs) fabricated with the product have good conductivity, dispersion and stability due to the synergetic effect between carbon and nanocrystalline CoS(Co9S8). Charge transfer through the CE/electrolyte interfaces is improved by dopamine-carbon combination. In the optimal case, PCE of 8.82% of the dye-sensitized solar cells (DSSCs) with the hybrid CEs was achieved, which is close to that of the cell with Pt (8.86%) CE, and is a 41.12% increase compared with that of CoS CE cell with the structure of photoanode/N719/electrolyte (I−/I3−)/CE. Moreover, stability of the cells with the composite CEs was greatly improved. The results demonstrate that the as-prepared composites are promising alternatives to Pt-CEs for high-performance DSSCs. The reported preparation method will guide further developments in highly efficient carbon-based catalysts for electrochemistry and energy related applications. [ABSTRACT FROM AUTHOR]

Pt counter electrodes (CEs) have been widely used in dye-sensitized solar cells (DSSCs) due to their high conductivity and electrocatalytic activity. However, industrialization of DSSCs is limited by shortcomings of Pt CEs such as being expensive, and weak corrosion resistance in electrolytes. Reported in this paper is two simple approaches to Pt-free Cu1.8S1−xSex CEs. Nanocrystalline Cu1.8S1−xSex CEs were fabricated via two processes, that is, a solvothermal process to Cu1.8S1−xSex powder followed by CE fabrication, and a solvothermal process and CE fabrication to Cu1.8S films followed by selenylation to Cu1.8S1−xSex CEs. Photoelectric conversion efficiencies (PCE) of 4.02% and 4.16% were achieved respectively by the as-fabricated Cu1.8S1−xSex CEs. Compared with the cells with Cu1.8S CEs fabricated by the same processes, increases of 19% and 45% were achieved, respectively. The PCE improvement comes from the enhancement of charge transfer at the CE/electrolyte interface induced by the selenylation of the CEs. [ABSTRACT FROM AUTHOR]

Self-amplified spontaneous emission in a free-electron laser has been proposed for the generation of very high brightness coherent x-rays. This process involves passing a high-energy, high-charge, short-pulse, low-energy-spread, and lowemittance electron beam through the periodic magnetic field of a long series of high-quality undulator magnets. The radiation produced grows exponentially in intensity until it reaches a saturation point. We report on the demonstration of self-amplified spontaneous emission gain, exponential growth, and saturation at visible (530 nanometers) and ultraviolet (385 nanometers) wavelengths. Good agreement between theory and simulation indicates that scaling to much shorter wavelengths may be possible. These results confirm the physics behind the self-amplified spontaneous emission process and forward the development of an operational x-ray free-electron laser., Generation of high-brightness (photon flux per frequency bandwidth per unit phase space volume) hard x-rays (photon energies greater than ~5 kev or wavelengths less than 2.5 A) has long been [...]