Characterization of Electrochemically Deposited Cu2O/TiO2 Bulk Hetero-Junction

• Main Authors: Hsu, Wen-Peng, 許文朋
• Other Authors: Chien, Chao-Hsin
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/62131815288986560613

碩士 === 國立交通大學 === 電子工程系所 === 98 === Dye-sensitized solar cell (DSSC) is an attractive candidate for solar application owing to its properties of low cost and shorter payback time. But the leakage of electrolyte caused by the degradation of sealant is hard to avoid. To further improve the long term stability of DSSC, solid-state material may be a good substitute for liquid electrolyte layer. In this thesis, Cu2O was used as a hole conductor and the Cu2O/TiO2 bulk hetero-junction is successfully formed. In the beginning, the electrochemical deposition method is used to deposit the Cu2O layer onto the nano-porous TiO2 film. Since the deposition conditions are dependent on the surface properties of matter on which we deposited, it is not easy to find the best condition of deposition. As a result, material analysis plays an important role in the experiment. With the help of XPS and XRD analyses, we can find the best condition from variety of conditions. Besides, with the SEM technique, the deposition rate of material can be investigated. It is believed that all of the techniques of material analysis can help us to form the Cu2O/TiO2 bulk hetero-junction successfully. Next, characteristics of the bulk hetero-junction are investigated with photo-electrical measurements and electrical impedance spectroscopy (EIS). With the results we obtained, it is though that the recombination mechanism limits the performance of junctions. It is critical to inhibit the number of recombination centers before applying to DSSC. As a result, many conditions are tested in order to further eliminate the recombination current. With the EIS measurement, we can investigate the variation of recombination mechanism form its frequency response and then find the better way to improve the junction performance. With the basic understanding of the bulk hetero-junction, some advanced measurements are performed to investigate the other characteristics of the junction. First, temperature dependence of junction is examined with the elevated temperatures. Second, optical condition of junctions is observed with different neutral density filters. Finally, the voltage response of junction is analyzed and the Mott-Schottky plot is obtained with the EIS results. With the Mott-Schottky result, the flat-band voltage is obtained and the complete model of band energy can be constructed. In this thesis, the Cu2O/TiO2 bulk hetero-junction is form successfully with electrochemical deposition method and suitable deposition conditions. And the characteristics of the junction are investigated by the measurement of DC IV and AC EIS techniques. Although deposition of Cu2O on dyed-TiO2 is not accomplished, the research of Cu2O/TiO2 bulk hetero-junction now will be a good help in the future study. Based on this research, it is believed that solid-state DSSC with better long term stability can be achieved with application of Cu2O material to DSSC.