| Summary: | 碩士 === 大葉大學 === 電機工程學系 === 97 === In this study, sol-gel TiO2 were used as the photo-anodes of the dye-sensitized solar cells(DSSC). The pristine nanocrystalline TiO2 , owing to the lack of internal built-in electric filed to swift off charge carriers and suppressing the recombination of photo-generated charge carriers, suffers from extremely low charge carrier density. Therefore, the key role to improve the activity of these photo-anodes is to retard (slow) the recombination of photo-generated charge carriers. Therefore, it is our goal to adapt concept by using a second semiconductor to sensitize the first one to overcome this problem. An efficient charge separation can be obtained by coupling two semiconductors particles. As the result of vectorial transfer of electrons, or inter-particles electron transfer (IPET), keeping the carriers of opposite sign reside on corresponding semiconductors, the recombination of photo-generated charge carriers were thus efficiently suppressed.
In this study, the process parameters in fabricating working electrodes had been investigated. Firstly, the finely grinded TiO2 paste was spin-coated on ITO glass with various layers at different speed. The as-deposited films were further annealed at different temperature. Finally, mesoporous TiO2 films with different thickness were obtained. The study found: Nanotechnology porosity by sintering of TiO2 compact structure easy to form thin film electrode, by adding different proportions of the polymers, an increase in the overall surface area, increased the amount of dye adsorption, absorption of visible light help to stimulate electronics, improved effectiveness of the overall conversion. The purpose of this study to look at a variety of different thickness and annealing temperature of TiO2 films produced by the working electrode, the photoelectric conversion efficiency of the impact. The photoanode with 1.55m in thickness seems to be the best choice of process parameters. Nevertheless, as the thickness of the photoanode is lower than 1.55m , the overall surface area as well as the amount of dye adsorption reduced. In addition, as the film thickness was over 1.68m, the as-deposited films is vulnerable to cracking during the drying which will deteriorate the film quality and the overall cell performance. In a preliminary study, annealing at 450oC resulted in the best cell performance and was chose for further studies.
Novel photoanode structures had been evaluated under simulated standard AM1.5 light source. In the two-tier structure (TCO / TiO2-SnO2 / TiO2 / Dye) decreased slightly at JSC in addition to 0.23 mA/cm2, VOC, FF, are rising. In the three-tier structure (TCO / SnO2 / TiO2-SnO2 / TiO2 / Dye), and single-layer structure (TCO / TiO2 / Dye) compared to the working electrode, photoelectric conversion efficiency of no significant impact.
In summary, the optimal process parameters seems to be that: TiO2 film thickness 1.55m. Photoelectric conversion efficiency of the largest structure of its single-layer(TCO/ TiO2(1.55m)/ Dye)；VOC=0.69V, JSC=10 mA/cm2, FF=0.56, =3.9%. Two-tier structure(TCO/ TiO2-SnO2/ TiO2(1.55m)/ Dye)；VOC=0.71V, JSC=9.77 mA/cm2, FF=0.64, =4.53%. Three-tier structure(TCO/ SnO2/ TiO2-SnO2 / TiO2(1.55m)/ Dye)；VOC=0.68V, JSC=10.1 mA/cm2, FF=0.57, =4%
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