Preparation And Investigation Of High-performance Dye-sensitized Solar Cells

Dye-sensitized solar cell (DSC) has attracted much attention since its discovery by Gratzel in 1991. After 20 years'development, its practical application has become more and more urgent. Focused on this subject, the DSC with high efficiency, stability, low-cost and practicability has been investigated systematically. In this dissertation, the research work includes the optimization of TiO2 nanoporous film of DSC, the improvement of DSC sealing method, the exchange of liquid electrolyte with quasi-solid state electrolyte, the development of large-scale DSCs modules and the introduction of a novel membrane counter electrode.Titanium dioxide nanotubes (TiNTs) were fabricated from commercial P25 TiO2 nano powders via alkali hydrothermal transformation. DSCs were constructed by application of TiNTs. Their photovoltaic performance and improvement mechanism have been investigated systematically. A metal-free organic dye (indoline dye D102) was used as a sensitizer. High conversion efficiencies of light to electricity of around 7.6% and 9.8% under illumination of simulated AM1.5 sunlight (100 mW/cm2) were achieved with TiO2 nanotube and P25 cells, respectively. And a Ru-composition dye was used as a sensitizer. DSCs were constructed by application of TiNTs and P25 nanoparticles with various weight percentages. Higher open-voltage (Voc), fill factor (FF), short-current (Isc) and efficiency (77) were obtained. The influence of the TiNT concentration on the performance of DSCs was investigated systematically. The electrochemical impedance spectroscopy (EIS) technique was employed to quantify the recombination resistance, electron lifetime and time constant in DSCs.Double layered sealing was designed and applied to the cells using two types of sealants with different functions. Compared with the solar cells sealed with a single sealant, the DSCs sealed by double sealants showed a superior performance after thermal stress aging at 80℃and 30℃. The long term stability of the fabricated solar cells was also tested at 30℃in the dark for over 1000 h. The thermal stability and degradation mechanism of DSCs was studied by using electrochemical impedance spectroscopy (EIS) technique. It was found that the cell were highly stable in cells with double layered sealing for over 1000 h aging at 30℃. The cell performance was even higher than that before aging.For further improve the stability, polymer gel electrolytes (PGEs) based on poly(acrylic acid)-poly(ethylene glycol) (PAA-PEG) hybrid have been prepared and applied to developed quasi-solid-state DSCs. The components of the TPGE were optimized in terms of the liquid electrolyte absorbency and ionic conductivity as well as electrochemical impedance spectroscopy (EIS). A quasi-solid-state DSC fabricated with optimized polymer gel electrolyte obtained an overall energy conversion efficiency of 5.13% under irradiation of 100 mW/cm2 (AM1.5).The commercialization of DSCs has been investigated. The fabrication techniques and procedures of large-scale DSCs modules connected in series have been developed for practical use. A series-connected DSC module with size of 10cm×10cm has been prepared successfully, and achieved a high conversion efficiency of 7.18%.A novel flexible counter electrode (CE) for DSCs has been fabricated using a micro-porous membrane as support media and sputtered Pt as the catalytic material. The fabricated DSC with the flexible membrane CE showed higher photocurrent density than the conventional sandwich devices based on chemically deposited Pt/FTO glass, achieving a photovoltaic conversion efficiency of 4.43%. The results provides useful information in investigation and development of stable, low-cost, simple-design, flexible and lightweight DSCs.