A new organic dye (BET) was synthesized and coadsorbed on TiO 2 nanoparticles to make mixed BET/ porphyrin-sensitized solar cells (DSCs). The BET is a boron dipyrromethene compound with one benzoic acid group attached to the meso position for its binding to the TiO 2 nanoparticles and two ethyl groups in the 3 and 3′ positions of pyrrolic units to broaden its absorption. Two ethyl groups are in the cis position, as revealed by its single-crystal X-ray diffraction analysis. The BET exhibits strong absorption in the green light region with an absorption maximum at 528 nm in CH 2 Cl 2 , which is complementary to the absorption spectrum of porphyrin dyes. When the BET coadsorbs on the TiO 2 nanoparticles with porphyrin dyes (TMPZn and LD12), the power conversion efficiencies increase from 1.09% to 2.90% for TMPZn-sensitized solar cells and from 6.65% to 7.60% for LD12-sensitized solar cells, respectively. The IPCE of the devices in the green light region increases dramatically due to the cosensitizing effect of BET. The fluorescence of BET in solution is partially quenched and that of porphyrin is enhanced in the presence of BET dye, indicating an intermolecular energy transfer from BET to the porphyrin dyes. The direct electron injection from BET to the TiO 2 conduction band was rather poor; only negligible photocurrent was observed. Comparative studies of absorption spectra on the TiO 2 nanoparticle films and electrochemical impedance at the dye/TiO 2 interface also indicate that the BET is an excellent coadsorber to prevent the aggregation of porphyrin dyes. An intermolecular energy transfer model is proposed to account for the observed photovoltaic enhancement of the cosensitization system.
Hierarchical porous activated carbon (AC) was obtained from corn stalk pith with a hierarchical macroporous nature, which is composed of cells of soft and spongy texture. The high specific surface area (2495 m 2 g-1) of the activated carbon (AC) was produced by the activation of corn stalk core (CSC) using potassium hydroxide at 700 °C. SEM, TEM and XRD were used to test the microstructure and crystallographic orientation of the carbon samples. The cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy were measured based on CSC-700. This sample had relatively low inner resistance of 1.0 Ω. The specific capacitance was 323 F g-1 in 6 mol L-1 KOH electrolyte at a current density of 0.1 A g-1 , and it still maintained very good cyclic stability with capacitance retention ratio of 97.9% (from 265.0 to 262.4 F g-1) at current density of 1.0 A g-1 for 1000 cycles.
Crack-free TiO(2) nanotube (NT) membranes were obtained by short time re-anodization of a sintered TiO(2) NT array on Ti foil, followed by dilute HF etching at room temperature. The resulting freestanding TiO(2) membranes were opaque with a slight yellow color having one end open and another end closed. The membranes were then fixed on transparent fluorine-tin-oxide glass using a thin layer of screen-printed TiO(2) nanoparticles (NPs) as a binding medium. It was found that low temperature treatment of the resulting NT/NP film under appropriate pressure before sintering at 450 °C was critical for successful fixation of the NT membrane on the NP layer. The resulting films with open-ends of NT membranes facing the NP layer (open-ends down, OED, configuration) exhibited better interfacial contact between NTs and NPs than those with closed-ends facing the NP layer (closed-ends down, CED, configuration). The cells with an OED configuration exhibit higher external quantum efficiency, greater charge transfer resistance from FTO/TiO(2) to electrolyte, and better dye loading compared to CED configurations. The solar cells with the OED configuration gave 6.1% energy conversion efficiency under AM1.5G condition when the commercial N719 was used as a dye and I(-)/I(3)(-) as a redox couple, showing the promise of this method for high efficiency solar cells.
Ultra-flexible, highly-conductive and fully-transparent μECoG electrode arrays made of PEDOT:PSS–ITO–Ag–ITO on thin parylene C successfully achieved neurophysiology recording.
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