Study On Modification And Photoelectric Properties Of ?-? Semiconductor/Titanium Dioxide Composite Films

Solar energy technology is one of the effective methods to solve the energy crisis and environmental pollution.High-efficiency and low-cost solar cells are the key to achieve solar energy conversion and application.Semiconductor quantum dots h ave many advantages for photosensitizers in the quantum dot sensitized solar cells?QDSCs?,such as good light stability,high extinction coefficient,adjustable band gap and multi-exciton effect.The photoelectric conversion efficiency may break through the Shockley-Queisser theoretical limitation?31%?and reach a higher conversion efficiency?44%?.QDSCs have received extensive attention and research from scientific researchers.Based on the structural characteristics of QDSCs,the photoelectrode composed of QDs photosensitizer and oxide film is the key to determine the photoelectric conversion efficiency.However,the low loading of QDs and the high electron-hole recombination rate limit the efficiency of QDSCs.On this basis,in order to improve the photovoltaic performance of solar cells,we try to improve the load quality of Cd S QDs and the charge transport performance of TiO₂ materials through the optimization methods of structural improvement,element doping and interface treatment of photoelectrodes.The main research contents are as follows:?1?The Sn-doped TiO₂?STO?nanosheet array film with large area and high energy{001}crystal plane was prepared by hydrothermal method.The research indicate d that Sn doping was beneficial to the formation of the mixed cationic compounds Sn_xTi_1-xO₂and doping energy levels.Sn-doped enhanced the light absorption ability and charge transport performance of TiO₂ nanosheet array film.Then,the successive ionic layer adsorption and reaction?SILAR?method was used to sensitize Cd S QDs on the surface of STO nanosheets.Sn doping could increase the number of active sites on the surface of TiO₂ nanosheets,which would make the distribution of Cd S QDs more uniform and dense.The photocurrent density of the Cd S/STO composite film improve d to the maximum 5.71 m A cm^-2.?2?The simultaneous etching and doping TiO₂?EWT?nanorod array film was prepared by hydrothermal method.The synergy between etching and doping was investigated.The amorphous shell had formed on the surface of TiO₂ nanorods.The shell could prevent the electrons from contacting the electrolyte again.W doping could cause the TiO₂ conduction band to move downward.And W⁶⁺would replace Ti⁴⁺,which could increase the electron density.These results improved the conductivity of the amorphous shell.The SILAR method was used to sensitize Cd S QDs on the surface of EWT nanorods.The amorphous etching shell increased the specific surface area and the number of active centers of the nanorods,thereby increasing the number and density of loaded QDs.These results maximized the photocurrent density of the Cd S/EWT composite film(7.05 m A cm^-2).?3?The Sn-doped TiO₂?STO?nanorod array film was prepared by hydrothermal method.The excellent characteristics of Sn doping enhance the light absorption ability and charge transport ability of the thin film.Afterwards,the STO nanorods were treated with hydrogen?H-STO?at different temperatures.Many oxygen vacancies and hydroxyl groups were formed on the surface of the nanorods.Hydrogen treatment extended the light absorption range to the visible light region.Meanwhile,hydrogen treatment promoted the separation and transport of charges.Then,the SILAR method was used to sensitize Cd S QDs on the surface of H-STO nanorods.The combined effect of Sn doping and hydrogen treatment greatly increased the den sity of active sites on the surface of H-STO nanorods.The synergy increased the load quality of Cd S QDs.Finally,the photocurrent density of the Cd S/H-STO composite film reached a maximum of 7.72m A cm^-2.