The Preparation And Photoelectric Performance Of The Sensitized Solar Cells Based On ZnO Nanorods Photoanodes

With the increasingly serious problem of the energy shortage, solar energy as a kind of renewable clean energy has attracted extensive attention of the researchers. The solar cells are photovoltaic devices which convert the solar energy directly into electrical energy. Recently, compared with the Si-based solar cells, the sensitized solar cells which include the dye sensitized solar cells（DSSCs） and quantum dot sensitized solar cells（QDSSCs） have received widely research due to their lower cost, simpler fabrication. The sensitized solar cell is mainly composed of photoanode, electrolyte and a counter electrode. Particularly, the photoelectrode serves not only as the carrier for electron transport but also a substrate for sensitizer absorption. In this paper, the influence of different content of noble metal Ag nanoparticles on the photoelectric performance of the Zn O NRs-based solar cells, the performance of different ratio of Zn O NRs embedded in TiO₂ NPs layer hybrid structures films based soar cells and the properties of various thickness of TOP ZnO NRs/Ti O2 NPs based solar cells were studied. The detailed results were summarized as follows.1. Using hydrothermal method, uniform-sized ZnO NRs were prepared on the transparent conductive glass FTO, then a series of ZnO/Ag composite structure films contain different content of Ag NPs were fabricated by using photo-reduction method. After sensitized with N719 and CdS, respectively, the light absorption and electron transport properties of the Ag NPs were examined. It was found that the loading-sensitizer enhanced due to the higher surface and the light absorption of the sensitizer increased because of the localized surface plasmon resonance（LSPR） of the Ag NPs. What’s more, Ag NPs acted as electron-hole separation centers due to the Schottky barriers at the Ag/ZnO interface. When the AgNO3 concentration is 1.0 mM, the highest power conversion efficiency（PCE） is 2.69% for QDSSCs and 2.96% for DSSCs, However the higher content of Ag NPs would aggregate to form large Ag-groups thus impairing the integrity of photoanode and partial Ag could be oxidized as Ag+ to act as electron-hole recombination centre which limit the electron transport. Further, the ZnO/Ag/TiO₂ based DSSCs were prepared to obtain a highest PCE of 4.09%.2. A hybrid structure of ZnO NRs/TiO₂ NPs used as photoanode for sensitized solar cells was fabricated first using doctor-blade method with the ZnO/TiO₂ paste to form a special ZnO seed layer within the TiO₂ NPs, then using hydrothermal method to grow ZnO NRs. The light scattering of ZnO NRs increases the light harvesting efficiency of soar cells and 1D structure of ZnO NRs contributes to the fast electron transport thus a increasing in the electron collection efficiency. However the heterostructure films with smaller surface areas result in less amount of dye molecule adsorption and thus lower values of light harvesting efficiency. Considering all the factors, the optical sample is 6 wt%-ZnO NRs/TiO₂ NPs, which is 3.95% for QDSSCs and 6.41% for DSSCs. To further study the fast electron transport and strong light scattering of ZnO NRs, the 27μm 6 wt%-ZnO NRs/TiO₂ NPs and bare TiO₂ NPs were fabricated, a higher power conversion efficiency of 7.13% was obtained.3. A heterostructure of TiO₂ NPs/ZnO NRs used as photoanode for sensitized solar cells is fabricated first using doctor-blade method with the TiO₂ paste then using hydrothermal method to grow ZnO NRs for different time to get various thickness of ZnO NRs. It turned out that with the increase of ZnO NRs thickness,an increase in light scattering was found. What’s more, the hybrid films with higher surface area result in more amount of dye molecule adsorption and thus higher values of light harvesting efficiency. The highest PCE is 4.85%, which is 64.4% higher than the bare TiO₂ –based DSSCs.