| Dye sensitized solar cells have attracted a lot of attention because of their advantages. In order to promote the electrochemical properies,we take the preparation of photoanodes and Ti O2 photoanodes surface modification to suppress the recombination processes as the subjects of our research. We explored the impact of different metal oxide coating on Ti O2 nanoparticle electrodes and the optimal conditions for Ti O2/Al2O3. At the same time, we also explored the impact of the electrolyte additives(Li ions, 4-tert-butylpyridine) on the charge transfer at the titanium dioxide/dye/electrolyte interface in a typical DSSC as well as the electrochemical properties of the devices. In this study, we also synthesized anatase Ti O2 nanorod through one-step hydrothermal method. The growth parameters and surface modification of Ti O2 nanorod photoanodes are investigated.The conclusions are drawn as following:(1) Ti O2 nanoparticle electrodes are coated with Mg O, Sr O, Al2O3, Zr O2 or Nb2O5 successfully. We studied the impact on the devices performance with Ti O2/Mg O,Ti O2/Sr O,Ti O2/Al2O3,Ti O2/Zr O2 or Ti O2/Nb2O5 composite film as the photonanodes. Except for Nb2O5, Ti O2 film coated with others supress the recombination rate between the photoinjected electrons and I-3, resulting in improvement in device performance. The device exhibits a power conversion efficiency of 6.92% at 100 m W cm-2air mass global(AM 1.5G) conditions when using Ti O2/Al2O3 composite film as the photonanode. And we studied the impact parameters on the devices performance such as dipping times and precursor concentrations when coating Al2O3. We find that recombination(2e- + I-3 â†' 3I-) is supressed effectively, when recursor concentration is 50 m M and dipping time is 60 s, which results in improvement in device performance. And the device exhibits best performance(Jsc=14.69 m A cm-2, Voc=670 m V, FF=0.71 and η=6.97%) at 100 m W cm-2air mass global(AM 1.5G).(2) We investigated the impact of Li ion and 4-tert-butylpyridine on Ti O2 photoanodes. We find that the increase of Li ion concentration in the electrolyte confers a downward displacement of conduction band edge upon Ti O2, which increases therecombination rate between photoinjected electrons and I-3. When Li ion concentration is 100 m M, the device exhibits the best performance(Jsc=14.67 m A cm-2, Voc=673 m V,FF=0.72 and η=7.11%) at 100 m W cm-2 air mass global(AM 1.5G). And we also find that the increase of 4-tert-butylpyridine concentration in the electrolyte confers a upward displacement of conduction band edge upon Ti O2, which supress the recombination rate between photoinjected electrons and I-3. When 4-tert-butylpyridine concentration is 0.5 M, the device exhibits the best performance(Jsc=14.27 m A cm-2,Voc=688 m V, FF=0.72 and η=7.04%) at 100 m W cm-2 air mass global(AM 1.5G).(3) We synthesized(1D) anatase Ti O2 nanorod through one-step hydrothermal method. The growth parameters such as reaction time, reaction temperature, ammonia concentration, ammonium chloride and isopropanol are investigated.The results show that all factors will influence morphology or crystalline of the Ti O2 nanorod. When using Ti O2 nanorod as the photoanodes, the device exhibits a power conversion efficiency of 5.56% at 100 m W cm-2air mass global(AM 1.5G), whereas the device exhibits a power conversion efficiency of 5.06% at 100 m W cm-2air mass global(AM1.5G) when Ti O2 nanorod photoanodes coated with Al2O3, in which short-circuit current density decreases significantly, but the open circuit voltage and the electron life increase.We also combine Ti O2 nanorod and the Ti O2 scattering as photoanodes, the device exhibits a power conversion efficiency of 6.13%. Comparing with the device using Ti O2 nanoparticle electrodes, open voltage and fill factor of the device are improved because nanorod is benefit for the charge Transmission and decreasing recombination. We also made photoanodes coating with Al2O3, our results reveal that recombinations are surpressed effectively, resulting in the increase of open voltage and fill factor, but the device exhibits better electrochemical performance when using Ti O2 nanorod as photoanodes. |
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