Fabrication And Photoelectrical Properties Of Quantum Dots Sensitized ZnO NSs/TiO₂ Nras Photoanode

As a representative of the third-generation solar cells, quantum dots sensitized solar cells?QDSSCs? have received more and more concerning because of their low production cost and high theoretical photoelectric conversion efficiency. However, up to now, the actual photoelectric conversion efficiency of QDSSCs is still low because of the low transfer rate and high recombination rate of photo-induced electrons. As the important part of QDSSCs, the photoanodes' structures directly influence the transfer and recombination of photo-induced electrons, which determines the final photoelectric conversion efficiency. One dimensional TiO₂ nanorod arrays provide a direct conduction pathway for photo-induced electrons, which is beneficial to the transfer of photo-induced electrons. In this thesis, a novel ZnO NSs/TiO₂ NRAs composite photoanode was constructed to suppress the recombination of photo-induced electrons and remain the fast transfer of photo-induced electrons, in order to improve the photoelectric conversion efficiency of QDSSCs. Specific work and results includes below aspects:?1? The TiO₂ nanorod arrays were prepared on FTO substrates via a facile hydrothermal process, and TiO₂ nanorod arrays were decorated by CdS quantum dots through a successive ionic layer adsorption and reaction?SILAR? method. QDSSCs with as-synthesized photoanode were fabricated, and the effects of hydrothermal time, quantum dots layers and polysulphide electrolyte and CuxS counter electrode on the photovoltaic performance of the QDSSCs were investigated. The results show that the QDSSCs have good performance when hydrothermal time is 10 h and quantum dots layers are 16 layers, respectively. Although the open circuit voltage of battery is reduced, the short circuit current density of the battery is increased when the electrolyte is replaced by polysulphide and the counter electrode is replaced by CuxS.?2? ZnO NSs/TiO₂ NRAs composite structures were fabricated by assembled the ZnO nanosheets on TiO₂ nanorod arrays via the chemical bath deposition method?CBD?. And CdS/ZnO NSs/TiO₂ NRAs structures were prepared by in situ depositing CdS quantum dots through a SILAR method. QDSSCs with as-synthesized photoanode were fabricated. The results show that the QDSSCs based ZnO NSs/TiO₂ NRAs can suppress the recombination of photo-induced electrons and increase the lifetime of electrons, which lead to the larger open circuit voltage, short circuit current density and photoelectric conversion efficiency rather than that of the QDSSCs based TiO₂ NRAs.?3? CdSe/CdS/Zn O NSs/TiO₂ NRAs composite structures were fabricated by in situ depositing CdSe on CdS/ZnO NSs/TiO₂ NRAs via the chemical bath deposition method?CBD? in order to expand the response range of QDSSCs to light. QDSSCs were fabricated with as-synthesized photoanode, and the effects of CdSe quantum dots' deposition time on the photovoltaic performance of the QDSSCs were investigated. The results show that the absorption edge is gradually red-shifting as the extension of deposition time. And the absorption edge remains stable when CdSe quantum dots is deposited for 3 hours, and the CdSe/CdS co-sensitized ZnO NSs/TiO₂ NRAs solar cells have good performance.