Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...

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Dye-Sensitized Solar Cells

Using a simple hydrothermal procedure, cobalt oxide (Co3O4) nanowires were in situ synthesized on three-dimensional (3D) graphene foam grown by chemical vapor deposition. The structure and morphology of the resulting 3D graphene/Co3O4 composites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. The 3D graphene/Co3O4 composite was used as the monolithic free-standing electrode for supercapacitor application and for enzymeless electrochemical detection of glucose. We demonstrate that it is capable of delivering high specific capacitance of ∼1100 F g–1 at a current density of 10 A g–1 with excellent cycling stability, and it can detect glucose with a ultrahigh sensitivity of 3.39 mA mM–1 cm–2 and a remarkable lower detection limit of <25 nM (S/N = 8.5).

3D Graphene–Cobalt Oxide Electrode for High-Performance Supercapacitor and Enzymeless Glucose Detection

Manganese-activated fluoride phosphors for high-efficacy warm white light-emitting diodes have been limited by low photoluminescence quantum yields. Here, Zhu et al. use an efficient cation exchange reaction to synthesize manganese phosphors with photoluminescence quantum yields as high as 98%.

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Highly efficient non-rare-earth red emitting phosphor for warm white light-emitting diodes

In the present review we try to give a comprehensive and most up to date view to the field, with an emphasis on the currently most investigated anodic TiO2 nanotube arrays. We will first give an overview of different synthesis approaches to produce TiO2 nanotubes and TiO2 nanotube arrays, and then deal with physical and chemical properties of TiO2 nanotubes and techniques to modify them. Finally, we will provide an overview of the most explored and prospective applications of nanotubular TiO2.

One-dimensional titanium dioxide nanomaterials: nanotubes.

Electrolytes in Dye-Sensitized Solar Cells

Zinc oxide (ZnO) nanosheets (ZnO-NS) were prepared for the photoanode of a dye-sensitized solar cell (DSSC), first by directly growing layered hydroxide zinc carbonate (LHZC) on an FTO substrate using a chemical bath deposition (CBD) method and then by transforming the LHZC into ZnO through pyrolysis at 300 °C. A light-to-electricity conversion efficiency (η) of 6.06% was achieved for the DSSC with ZnO-NS as its photoanode, under 100 mW cm−2 illumination, and this (η) was found to be much higher than that of the DSSC with ZnO nanoparticles (ZnO-NP) as the photoanode (2.92%). The far superior performance of the DSSC with ZnO-NS is essentially attributed to (i) higher effective electron diffusion coefficient of ZnO-NS (3.59 × 10−3 cm2s−1) than that of ZnO-NP (1.12 × 10−3 cm2s−1), and to (ii) higher dye loading on ZnO-NS (2.66 × 10−7 mol cm−2) than that on ZnO-NP (1.99 × 10−7 mol cm−2); this higher electron diffusion coefficient and dye-loading are attributed to the specific morphology of the ZnO-NS. A further improvement in the efficiency of the DSSC with ZnO-NS could be achieved through the electrophoretic deposition (EPD) of a very thin layer (3 μm) of titanium dioxide nanoparticles (TiO2-NPs of average size 14 nm) onto the ZnO-NS layer (12 μm). Notwithstanding a decrease in the effective electron diffusion coefficient (3.07 × 10−3 cm2s−1) in the TiO2-NP/ZnO-NS film, with reference to that in the ZnO-NS film (3.59 × 10−3 cm2s−1), a far higher cell efficiency was obtained in favor of the cell with TiO2-NP/ZnO-NS (7.07%), compared to that of the cell with bare ZnO-NS (6.06%); this enhancement in the η of the cell with TiO2-NP/ZnO-NS is ascribed to an increased dye-loading in favor of its cell (3.92 × 10−7 mol cm−2), with reference to that in the case of the cell with bare ZnO-NS (2.66 × 10−7 mol cm−2). As against the common ruthenium dyes, such as N3 and N-719, a metal-free dye, coded as D149, was used in this research. The efficiency achieved for the best DSSC in this work is the highest ever reported for a DSSC with ZnO as the main semiconductor material.

Highly efficient dye-sensitized solar cell with a ZnO nanosheet-based photoanode

Cobalt oxide acicular nanorods with high sensitivity for the non-enzymatic detection of glucose.

InGaN∕GaN multiple-quantum-well (MQW) light-emitting diodes with varied InGaN quantum well thicknesses are fabricated and characterized. The investigation of luminous efficiency versus current density reveals a variety of efficiency droop behaviors. It is found that the efficiency droop can be drastically reduced by increasing the quantum well thickness of the MQW structures. On the other hand, relative internal quantum efficiency (IQE) measurements indicate that a thinner well results to higher IQEs owing to the greater spatial overlap of electron and hole distribution functions.

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Efficiency droop behaviors of InGaN∕GaN multiple-quantum-well light-emitting diodes with varying quantum well thickness

Electrode modified with a composite film of ZnO nanorods and Ag nanoparticles as a sensor for hydrogen peroxide

A flexible photoanode with zinc oxide film on titanium foil was prepared and its application in a dye-sensitized solar cell (DSSC) was investigated. The ZnO film with a mosaic structure, composed of densely packed ZnO nanosheets (ZnONS), was obtained by calcining a film of layered hydroxide zinc carbonate (LHZC), which was previously grown directly on a Ti foil via chemical bath deposition (CBD). The highly porous ZnONS film with a film thickness of about 25 μm could be facilely prepared within 4 h under CBD conditions. Owing to the intrinsic properties of the ZnONS film, i.e., high porosity, high surface area, and effective electron transport, a solar-to-electricity conversion efficiency (η) of 5.41% was achieved for the pertinent back-illuminated DSSC, which is the highest ever reported value for a back-illuminated DSSC based on a ZnO photoanode. The effect of the sputtering time of platinum (Pt) and iodine concentration on the photovoltaic performance of the DSSC were also investigated. Films on the substrates were characterized by X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Transmission spectra were obtained to characterize Pt films. Electrochemical impedance spectra (EIS) were obtained to analyze the charge transfer resistance and Warburg diffusion process in the DSSCs. Incident photon-to-current conversion efficiency (IPCE) curves were used to support the behavior of short-circuit photocurrent (JSC) of DSSCs and also to calculate its values. Electron lifetimes in photoanodes were determined using Bode-phase plots.

Yi Hsuan Lai

Papers

Highly efficient dye-sensitized solar cell with a ZnO nanosheet-based photoanode

Cobalt oxide acicular nanorods with high sensitivity for the non-enzymatic detection of glucose.

Efficiency droop behaviors of InGaN∕GaN multiple-quantum-well light-emitting diodes with varying quantum well thickness

Electrode modified with a composite film of ZnO nanorods and Ag nanoparticles as a sensor for hydrogen peroxide

Fabrication of a ZnO film with a mosaic structure for a high efficient dye-sensitized solar cell