Hunan Key Laboratory for Super microstructure and Ultrafast Process

Changsha, China

Hunan Key Laboratory for Super microstructure and Ultrafast Process

Changsha, China

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Wang X.,Central South University | Wang X.,Hunan Key Laboratory for Super microstructure and Ultrafast Process | Yang B.,Central South University | Yang B.,Hunan Key Laboratory for Super microstructure and Ultrafast Process | And 5 more authors.
Current Applied Physics | Year: 2015

TiO2 films with ordered porous structure were prepared by freezing. By simply freezing wet TiO2 film on a cold copper plate, ice crystals could grow from bottom of film. Removing such ice crystals then led to ordered, micro-sized pores in the films. With assistance of scanning electron microscopy and N2 adsorption-desorption isotherms, micro-structural properties of the films were studied. Coarsening behavior of ice crystals was analyzed based on evolvement of the micro-structure. It was found that, both larger film thickness and longer freezing time were beneficial for the formation of ordered porous structure, which was caused by enhanced ice crystals growth. The films were then used to fabricate photoanode of dye sensitized solar cells, of which the photo-to-electric power conversion efficiency was evaluated. It was observed that, solar cell made of ordered porous TiO2 film came out with 13% larger photo-current density comparing to that made of conventional doctor blading method, which is due to the enhanced light scattering by the ordered porous structure. © 2015 Elsevier B.V. All rights reserved.


Zhou C.,Central South University | Zhou C.,Hunan Key Laboratory for Super microstructure and Ultrafast Process | Wang X.,Central South University | Wang X.,Hunan Key Laboratory for Super microstructure and Ultrafast Process | And 7 more authors.
Optoelectronic Devices and Integration, OEDI 2015 | Year: 2015

TiO2 films with ordered porous structure were prepared by freezing and used to fabricate dye sensitized solar cells. Due to the enhanced light scattering by the ordered porous structure, Increase of 13% in photo-current density was obtained despite of lower dye loading. © OSA 2015.


Zhu K.,Central South University | Zhu K.,Hunan Key Laboratory for Super microstructure and Ultrafast Process | Tang H.,Central South University | Tang Y.,Central South University | Xia H.,Central South University
Optics and Laser Technology | Year: 2014

We proposed a scheme that converts a sine-Gaussian beam with an edge dislocation into a dark hollow beam with a vortex. Based on the gyrator transform (GT) relation, the closed-form field distribution of generalized sine-Gaussian beams passing through a GT system is derived; the intensity distribution and the corresponding phase distribution associated with the transforming generalized sine-Gaussian beams are analyzed. According to the numerical method, the distributions are graphically demonstrated and found that, for appropriate beam parameters and the GT angle, dark hollow vortex beams with topological charge 1 can be achieved using sine-Gaussian beams carrying an edge dislocation. Moreover, the orbital angular momentum content of a GT sine-Gaussian beam is analyzed. It is proved that the GT retains the odd- or even-order spiral harmonics structures of generalized sine-Gaussian beams in the transform process. In particular, it is wholly possible to convert an edge dislocation embedded in sine-Gaussian beams into a vortex with GT. The study also reveals that to obtain a dark hollow beam making use of GT of cos-Gaussian beams is impossible. © 2014 Elsevier Ltd.


Xia X.,Central South University | Xia X.,Hunan Key Laboratory for Super microstructure and Ultrafast Process | Yang B.,Central South University | Yang B.,Hunan Key Laboratory for Super microstructure and Ultrafast Process | And 4 more authors.
Materials Research Express | Year: 2015

Bending is usually used to test durability of flexible transparent and conductive films. Due to the large stress incurred by this technique, bending has always been observed to deteriorate conductance of electrodes such as indium tin oxide film. In contrast, we here demonstrate that bending could be used to improve conductance of silver nanowire-based flexible transparent and conductive films. The enhanced conductance is due to improved contact between nanowires, which was favored by the hydrogen bond formed between residential polyvinylpyrrolidone (PVP) on silver nanowire and TiOx nanoparticles pre-coated on the substrate. The enhanced conductance was found to be affected by bending direction; bending towards the substrate not only yielded quicker decrease in sheet resistance, but also showed better film conductance than bending towards the nanowires. Then, with assistance of surface modification of substrate and ultra-long silver nanowires (averaged at 124 μm, maximum at 438 μm), optoelectronic performance of 90.2% (transmittance at 550 nm) and 12.5ωsq-1 (sheet resistance) has been achieved by bending. Such performance was better than commercialized flexible ITO films, and even competed with that obtained from thermal annealing at temperature of 200 °C. Moreover, Fourier transfer infrared (FTIR) spectroscopy study showed strong coordination between C=O(heterocyclic ring of PVP) and silver atoms, showing obvious capping behavior of PVP on silver nanowires. © 2015 IOP Publishing Ltd.

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