Study On The Process And Properties Of CdSe/CdS Heterojunction Photosensitized TiO₂

Nanocrystalline TiO₂ is usually used as a wide bandgap semiconductor material in photoanodes for sensitized solar cells owing to its advantages including suitable conduction band position with a bandgap of 3.2 eV,stable chemical and physical properties,and low cost.CdSe and CdS with band gap of1.7 eV and 2.25 eV,respectively,at room temperature,can directly use the energy of visible light.They are widely used to sensitize,either alone or together,nanocrystalline TiO₂ for sensitized solar cells to expand the light absorption range and enhance the photoelectric conversion efficiency.In addition,TiO₂morphology has significant influence on the photoelectronic properties of the photoanode.In present study,anatase TiO₂ nanosheets and rutile TiO₂ nanorods array films were prepared on conductive glass by hydrothermal synthesis method.The TiO₂ nanosheets and TiO₂ nanorods were co-sensitized with Cd S and CdSe to form heterojunction composite films and the number of deposition cycles for co-sensitized TiO₂ was optimized,then the influence of heat-treatment temperature on the photoelectric properties of heterojunction composite films was investigated.?1?CdSe?4?/CdS?5?nano films with better photoelectric properties were fabricated on conductive glass by cyclic voltammetry.The short circuit current density is 1.78 mA·cm^-22 and the photoelectric conversion efficiency is 0.29%;The best photoelectric property of CdSe?4?/CdS?5?heterojunction nanofilms was obtained by heat treating at 150?for 2 h,the short-circuit current density is1.96 mA·cm^-22 and the photoelectric conversion efficiency is 0.83%.?2?Cd Se?5?/CdS?3?/TiO₂ heterojunction composite films with better photoelectric properties were fabricated on TiO₂ nanosheets arrays thin film by cyclic voltammetry.The short-circuit current density is 1.78 mA·cm^-2,the photoelectric conversion efficiency is 1.72%;After heat-treated at 150?for 2 h,the CdSe?5?/CdS?3?/TiO₂ nanosheets heterojunction composite thin films show best photoelectric property.The short-circuit current density is 2 mA·cm^-2,and the photoelectric conversion efficiency is 2.24%,which maybe ascribed to the existence of ternary compound CdS_1-xSe_x after heat-treatment.?3?Cd Se?5?/CdS?3?/TiO₂ heterojunction composite films with better photoelectric properties were fabricated on TiO₂ nanorods arrays thin film by cyclic voltammetry.The short-circuit current density is 1.39 mA·cm^-2,the photoelectric conversion efficiencies is 0.94%;After heat-treated at 350?for 2h,the CdSe?5?/CdS?3?/TiO₂ nanorods heterojunction composite thin films show best ophotoelectric property.The short-circuit current density is 1.98 mA·cm^-2,and the photoelectric conversion efficiency is 0.95%.