Study of Electron Behaviors in Structure Modified Dye Sensitized Solar Cells

• Main Authors: Yu-Yen Kuo, 郭宇彥
• Other Authors: Chao-Hsin Chien
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/80893226108186200249

碩士 === 國立交通大學 === 電子工程系所 === 96 === To improve the energy transfer efficiency of dye sensitized solar cell furthermore and thus lead to more convenient usage of solar energy, complete knowledge of DSSC at present stage is necessary. In this dissertation, DSSC with three different structures were fabricated and the behaviors of electrons for each were analyzed through developed photo-electrical methods. In the start, basic properties of normal DSSC were examined and characterized. Developed theories about the working principle of DSSC, light absorption, electron injection and transportation, and the basics of measurement methods for analyzing electrons behavior were reviewed separately. With a preliminary understanding of conventional DSSC, the well known efficiency enhancement method, the passivation of TiO2 by titanium tetrachloride, was applied; the photo-electrical improvements were obviously observed from experimental results. To discover the cause of the enhancements, the electrons behaviors were measured. The recombination of electrons was inhibited when compared with non-passivated devices (near one ordered difference in the time constants) while the diffusion remains almost the same. It was thought that the inhibition of recombination be mainly due to the variation of surface states according to DOS measurement results. Because of the limitation on the diffusion length, it is preferred to achieve better absorption in thinner layer; then, a light scattering structure was applied to conventional DSSC by different sized nano-crystal. The conditions of the fabrication of scattering layer were tested and an optimized process was achieved to derive a uniform morphology of the scattering layer. With the application of the scattering layer, the enhancement of absorption was observed and the photo-voltage is enhanced in thinner layered devices. Based on observed experimental results, it was thought that the preliminary limiting factor for DSSCs at present stage be the low electron collection efficiency due to the low diffusivity in nano-crystallite film. To accelerate electron transportation, ordered nano-tube structure was fabricated and applied to DSSC successfully. Basic characterizations were done and some improvements were obtained while some disadvantages were expected to be overcome with advanced modifications in research afterward. In this dissertation, DSSCs with three different structures (conventional, scattering layer applied, and nano-tube applied) were fabricated and characterized. Different photo-electrical behaviors were observed in these devices due to the different nature of structural issues. Based on this research, it is believed that a much more efficient solar cell could be implicated.