Study on the Micro-Arc Grown Anatase TiO2 Films on Titanium Plate and Their Sensitized Solar Cell Efficiency

• Main Authors: Hing-fang Li, 李幸芳
• Other Authors: J. L. He
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/88397260981238642853

碩士 === 逢甲大學 === 材料科學所 === 95 === In past years, metallic materials have been regarded as main materials in traditional industry. However, the demand has been gradually replaced from metallic materials to light and functional metals and alloys with high commercial value. Among these functional metals, titanium has attracted much attention due to its extremely good corrosion resistance, high strength, light weight and good ductility, etc. However, in form of titanium dioxide, it has been applied in semiconductor sensor, bactericidal photo-catalytic materials and dye-sensitized solar cell (DSSC) all based on its photocatalytic property. It is known that titanium dioxide had a wide energy band gap and its microstructure fabricated by micro-arc oxidation (MAO) dominated photovoltaic efficiency of the DSSC. It is expected to produce an ideal TiO2 electrode with larger specific surface area on the titanium surface and capable of absorbing dye efficiently. However, microstructure could be changed by means of different ways such as heat treatment (usually for 400-600 ℃) that could affect phase structure of oxide layer and acid-pickling that could change its surface morphology or get rid of surface impurity. In this study, the porous anatase titanium dioxide thin film was grown on the titanium thin plate by MAO. Then the Ti / TiO2 +N3 dye / I2+LiI electrolyte / ITO inversed-type solar cell device was constructed. In this study, microstructure of micro-arc oxided titanium dioxide films and post acid-pickling were studied. Photovoltaic efficiency of the assembled DSSC devices was evaluated. The results indicate that micrometer-scale porous anatase TiO2 film can be fabricated by MAO and predominantly composed of anatase phase and minor rutile phase. By increasing current density, oxide film thickness is increased. This allows absorption of dye more efficiently. The overlarge current density led to decrease the amount of anatase phase. The effect of voltage on photocurrent is proportional to current density. When MAO treatment time was extended under low current density of 0.05 A/cm2, oxide layer thickness gradually reaches a constant value and the corresponding short-circuit photocurrent gradually increases to a constant value about 9.5 µA/cm2. However, in constant voltage of 500 V, the extended the MAO treatment time results in excess joule heating and large amount of rutile structure is created. This significantly decreases the short-circuit photocurrent from 11 µA/cm2 for 10 min to 2 µA/cm2 for 120 min. The acid-pickling, gives rise to the change in surface morphology. However, with increased acid-pickling time in sulfuric acid solution, surface morphology also gives significant change. Acid-pickling for 72 h, surface blossomed into the submicron surface morphology and it is good for dye absorbing and performs the highest short-circuit photocurrent�nof�n��5 �n�嫀/cm2. In summary, anstase titanium dioxide film can be fabricated on titanium plate by MAO. Micrometer scale porosity gives short-circuit photocurrent about ��5 �n�嫀/cm2 after parameter and acid-pickle.