Research On Dye-Sensitized Solar Cells Based On Novel Electrodes

With the increasing depletion of traditional energy sources（such as oil, coal, natural gas, etc.） and the environmental pollution is more and more serious, the development of new energy sources has become one of the hot research topics. Solar energy is a clean energy with the advantages of inexhaustible andsafety, so it has a good application prospect. Compared with the traditional photovoltaic devices, dye sensitized solar cells（DSSCs） have been focusing on because of their low cost, simple preparation and excellent performance. DSSC is mainly composed of photoanode, dye, electrolyte and counter electrode. High performance of counter electrode and photoanode is very important for improving the performance of DSSC. Therefore, this paper mainly does the following work:（1） A sponge like cobalt sulfide / graphene oxide（CoS/GO） film was fabricated on the conductive glass by the methods of electrophoretic deposition and ion exchange method. Then the CoS/GO film was transformed into CoS/reduced graphene oxide（CoS/rGO） by the treatments of sodium hydroxide and sulfuric acid solution. The CoS/rGO electrode has better conductivity and catalytic activity compared to the pure CoS, and the photoelectric conversion efficiency of DSSC can reach to 9.39%.（2） A highly efficient and transparent CoS/rGO counter electrode was prepared by hydrothermal method, and the effect of GO concentration on the performance of the electrode was studied. When the concentration of GO was 0.10 mgmL-1, the CoS/rGO0.10 counter electrode had good electrical conductivity and excellent catalytic activity on the I3-/I- of the electrolyte. With the front and back of the irradiation of the incident light intensity（100 mWcm-2）, the CoS/rGO0.10 counter electrode can make the DSSC photoelectric efficiency reached 8.38% and 9.82%, and was higher 19.17%than that of DSSC with Pt counter electrode（front irradiation）.（3） To study the effect of ammonia in the electrodeposition process of CoS and NiS on the conductive glass. The study found that the ammonia concentration in electrodeposition bath and scanning cycles had important influence on the performance of counter electrode. When the amount of ammonia respectively were 2 ml and 1 ml in 50 ml deposition solution and the scanning cycles was 4, CoS and NiS counter electrodes showed best conductivity and catalytic activity. The power conversion efficiencies of the with the CoS and NiS electrodes were 9.23% and 9.65%, respectively, which were higher than that of the DSSCs with CoS and NiS electrodes（prepared in neutral or acidic conditions）, and were higher than that of the DSSC with Pt electrode.（4） There were doping modification for Co₉S₈ nanotube, which was prepared by a two-step hydrothermal method. The products were flower-like microspheres CoNi2S4/NiS and CoMoO₄/Co₉S₈ hybrid nanotube, then prepared CoNi2S4/NiS and CoMoO₄/Co₉S₈ counter electrode by spin coating. Compared with pure CoNi2S4 and NiS, microspheres CoNi2S4/Ni S has larger specific surface area, and made the electrode has better conductiviy and catalytic activity and the efficiency of DSSC can be reached 8.81%. So CoNi2S4/NiS is a low-cost and high-performance electrode material. The surface of CoMoO₄/Co₉S₈ hybrid nanotubes were rougher than that of Co₉S₈ nanotubes. And cyclic voltammetry, impedance and Tafel test showed that CoMoO₄/Co₉S₈ electrode exhibited more excellent conductivity and catalytic activity. Furthermore, the powder conversion efficiency of DSSC can reach to 8.60%, which has greatly improvment than that of DSSCs with Co₉S₈ and Pt electrodes（7.69% and 8.13%）.（5） A NiO layer was prepared on the surface of TiO₂ photoanode by a hydrothermal method. The NiO layer not only increased the amount of dye adsorbed on the TiO₂/NiO photoanode and but also improved the light harvest capacity. And UV-Vis spectra of TiO₂/NiO showed a absorption increase in the range of 400 800 nm. By electrochemical analysis, compared with the TiO₂ optical anode, the TiO₂/NiO anode showed shorter electron transfer time, longer electron lifetime and higher electron collection efficiency. Therefore, the introduction of the NiO layer can effectively reduce the electron transfer impedance, thus reducing the electron recombination reaction. The power conversion efficiency of DSSC based on the TiO₂/NiO anode can reach 8.93%, which was higher 9.30% than that of DSSC assembled by the pure TiO₂ anode.