Yu-Hsun Nien

Effect of Different Graphene Oxide Contents on Dye-Sensitized Solar Cells

Graphene/TiO2 composite films were deposited on fluorine-doped SnO2-coated conductive substrates by spin coating acting as photoelectrodes of dye-sensitized solar cells. The graphene/TiO2 composite films were characterized by scanning electronic microscopy, an X-ray diffractometer, a UV-visible spectrometer, and electrochemical impedance spectroscopy. Nyquist plots showed the decrease of impedance, in which electron transport rate was promoted. The photovoltaic properties showed that the incorporation of graphene could increase the short-circuit current density and photoelectric conversion efficiency. However, an excessive incorporation of graphene led to the enhancement of charge recombination and the reduction of photoelectric conversion efficiency. The graphene/TiO2 composite film with 1.5-mL graphene oxide solution obtained the optimal photoelectric conversion efficiency of 5.26%.

Fabrication and Photovoltaic Properties of Dye-Sensitized Solar Cells Modified by Graphene Oxide and Magnetic Bead

In this letter, graphene oxide (GO) and magnetic bead (MB) were incorporated into titanium dioxide (TiO2) photoelectrode by electrophoretic deposition and spin coating. The structure of TiO2 photoelectrode was fabricated into a double-layer structure and the effects of GO and MB on the internal structure of dye-sensitized solar cells (DSSCs) were investigated. This letter indicated that GO and MB could enhance the photovoltaic performances of DSSC, which made the photovoltaic conversion efficiency (η) of DSSC achieve 4.63%. This improvement could be attributed to the high conductivity of GO and good dispersion of MB.

The Influence of Different Annealing Temperatures on Graphene-Modified TiO 2 for Dye-Sensitized Solar Cell

In this study, graphene/TiO2 composite films at different annealing temperatures from 450 to 650 °C acted as photoelectrode of dye-sensitized solar cell (DSSC). The graphene/TiO2 composite films were characterized by scanning electronic microscopy, X-ray diffractometer, and electrochemical impedance spectroscopy. The Nyquist plot is built to simulate the redox reaction of internal device at the heterojunction by an equivalent circuit model. It is useful to analyze the component structure and promote photovoltaic conversion efficiency of DSSC. According to the experiment results, the optimal annealing temperature of graphene/TiO2 composite film was 550 °C, where the open-circuit voltage was 0.74 ± 0.01 V, the short-circuit current density was 14.17 ± 0.32 mA/cm2, the fill factor was 51.00 ± 1.95%, and the photovoltaic conversion efficiency was 5.34 ± 0.12%.

The Incorporation of Graphene and Magnetic Beads Into Dye-Sensitized Solar Cells and Application With Electrochemical Capacitor

In this study, the titanium dioxide (TiO2) photoelectrode of a dye-sensitized solar cell (DSSC) was fabricated into a double-layer structure, which was made up of a TiO2/graphene/magnetic bead layer and a TiO2 layer by the spin coating method and electrophoretic deposition. The effects of graphene and magnetic bead for photovoltaic performances of the DSSC were investigated by X-ray diffraction, solar simulator, ultra-violet (UV)-visible spectrometer, and electrochemical impedance spectroscopy. According to the experimental results, graphene had the higher specific surface area to improve the dye loading of the DSSC and magnetic bead used its ability for dispersion and charge transfer to enhance the electron transportation in the DSSC, which made the photovoltaic conversion efficiency of DSSC achieve 5.70%. Moreover, DSSC with incorporation of graphene and magnetic bead was combined with electrochemical capacitor, which had the specific capacitance of 4.15 F/g to store energy from DSSC. Then, the electricity stored from electrochemical capacitor was used to drive the light-emitting diode (LED) for work.

Analysis of Different Series-Parallel Connection Modules for Dye-Sensitized Solar Cell by Electrochemical Impedance Spectroscopy

The internal impedances of different dye-sensitized solar cell (DSSC) models were analyzed by electrochemical impedance spectrometer (EIS) with an equivalent circuit model. The Nyquist plot was built to simulate the redox reaction of internal device at the heterojunction. It was useful to analyze the component structure and promote photovoltaic conversion efficiency of DSSC. The impedance of DSSC was investigated and the externally connected module assembly was constructed utilizing single cells on the scaled-up module. According to the experiment results, the impedance was increased with increasing cells connected in series. On the contrary, the impedance was decreased with increasing cells connected in parallel.

Analysis of different dye-sensitized solar cell models by electrochemical impedance spectroscopy

In this study, the internal impedances of different dye-sensitized solar cell (DSSC) model were analyzed by electrochemical impedance spectrometer (EIS) with an equivalent circuit model. The Nyquist plot was built to simulate the redox reaction of internal device at the hetero-junction. It was useful to analyze the component structure and promote photovoltaic conversion efficiency of DSSC. The impedance of DSSC was investigated and the externally connected module assembly was constructed utilizing single cells on the scaled-up module. According to the experiment results, the impedance was increased with increasing cells connected in series. On the contrary, the impedance was decreased with increasing cells connected in parallel.

Photovoltaic Analysis of Platinum Counter Electrode Modified by Graphene Oxide and Magnetic Beads for Dye-Sensitized Solar Cell

Platinum (Pt) is widely used for counter electrode of dye-sensitized solar cell (DSSC). In order to improve the electro-catalytic ability of Pt counter electrode for DSSC, the graphene oxide (GO) and magnetic beads (MBs) were added into titanium dioxide (TiO2) colloid to modifying Pt-counter electrode. GO with high specific surface area could be used as the electrocatalyst for triiodide reduction in DSSC. Because of its high charge carrier mobility and photocatalytic activity, MBs could enhance the photovoltaic properties of DSSC. Moreover, the effects of Pt counter electrode modified by GO and MBs for DSSC were investigated by X-ray diffraction, solar simulator, and electrochemical impedance spectroscopy. Compared with the photovoltaic conversion efficiency (PCE) of 2.31% of the conventional DSSC using Pt counter electrode, the catalyst properties of Pt counter electrode with GO and MBs had been improved and the PCE achieved 3.62%.

Photovoltaic Performance Analysis of Dye-Sensitized Solar Cell With ZnO Compact Layer and TiO 2 /Graphene Oxide Composite Photoanode

In this paper, the photoanode of dye-sensitized solar cell (DSSC) was fabricated as a double layer structure, where graphene oxide (GO) was incorporated with titanium dioxide (TiO2) film onto the ZnO compact layer. The photovoltaic characteristics, crystal structures, morphologies, and electrochemical impedance were investigated. According to the experimental results, the photovoltaic performance of DSSC was improved with the modification of ZnO compact layer and GO. The phenomenon can be attributed to the higher specific surface area of GO and the property of forming an energy barrier between the substrate and TiO2 film for ZnO compact layer, which can inhibit the electron-hole recombination.

Investigation on Iodine Concentration of Electrolyte for Dye-Sensitized Solar Cell With Platinum Counter Electrode Modified by Graphene Oxide and Magnetic Beads

In this study, we used graphene oxide (GO) and magnetic beads (MBs) to modify the dye-sensitized solar cell (DSSC). The titanium dioxide (TiO2) colloid was mixed with GO and MBs which was deposited on the top of platinum-counter electrode. In addition, we measured the photovoltaic performances of dssc with different iodide concentrations of electrolyte. Furthermore, we investigated the photovoltaic performances of DSSC under different light intensities. The DSSC achieves a photovoltaic conversion efficiency of 6.78% under the light intensity of 30 mw/cm2 for the electrolyte of 0.0125 m iodide.

Fabrication and Photovoltaic Properties of Dye-Sensitized Solar Cells Based on Graphene–TiO 2 Composite Photoelectrode With ZnO Nanowires

In this paper, the photoelectrode of dye-sensitized solar cell (DSSC) was fabricated into a double-layer structure on the fluorine-doped tin oxide glass, which was synthesized by a graphene oxide–titanium dioxide composite layer (GO–TiO2), and a zinc oxide nanowires (ZNWs) layer. The morphology and effects of double layer were investigated by the field emission scanning electron microscopy, UV-visible spectrometer, and solar simulator. The enhancement of the photovoltaic performances of DSSC could be attributed to the high specific surface area of GO and high electron mobility of zinc oxide. Besides, the equivalent circuit and electrochemical properties of GO–TiO2/ZNWs double structure were also investigated by electrochemical impedance spectroscopy.