Study On TiO₂ Composite Photoanode Of Dye-sensitized Solar Cells

As the core component of the dye sensitized solar cell（DSSCs）,the photoanode has an extremely important effect on the performance of DSSCs.At present,the properties of DSSCs can be effectively improved by Ion doping modification of photo anode materials and the preparation of the composite photoanode.Accordingly,an anatase TiO₂ single crystal nanorods（TiO₂ NRs）is synthesized by a one pot solvothermal method as the barrier layer of the photoanode.On the basis of the barrier layer,the transition metal elements（W,Mo）for a single doped TiO₂composite photoanode is prepared by hydrothermal method.After that the photo-electric performance of the assembled DSSC is tested.The main contents of the work are as follows:（1）Anatase TiO₂ single crystal nanorods（TiO₂ NRs）is synthesized by a one pot solvothermal method.Firstly,different concentrations of TiO₂ NRs solution are successfully prepared,and then the TiO₂ NRs barrier layer with different thickness is obtained by two step spin coating.Then,the TiO₂ NRs barrier layer and the TiO₂mesoporous layer constitute the DSSCs composite photoanode.Because of its good electronic transmission channel,the TiO₂ NRs barrier layer can enhance the electronic transmission rate and improve the high photoelectric performance of DSSCs.Finally,when the thickness of the TiO₂ NRs barrier layer is 88.58 nm(Ti O₂ NRs concen-tration is 0.245 mol·L^-1),the photoelectric conversion efficiency（PCE）is 8.44%.（2）The W⁶⁺doped Ti O₂ colloid is prepared by sol-gel method and hydrothermal method.TiO₂ NRs with a thickness of 88.58 nm is used as the barrier layer,TiO₂mesoporous layer is scraped on the barrier surface by template method.Then,the W⁶⁺doped TiO₂ composite photoanode is successfully prepared.Conclusively,when the TiO₂ photoanode is doped with W⁶⁺,the spectral response region is extended to the visible spectrum band.Therefore the short circuit current density(J_sc)and PCE of DSSCs have been significantly increased.And when the doping amount of W⁶⁺is0.2%,the J_sc is 18.05 mA·cm^-2,and the PEC is 9.52%.（3）The Mo⁵⁺doped TiO₂ composite photoanode is successfully prepared by sol-gel method,hydrothermal method and the template method.It can increase the adsorption capacity of the dye and reduce the recombination of electron hole.When the Mo⁵⁺doping amount is 0.1%,the J_sc of DSSCs is 18.54 mA·cm^-2,and the PCE is 9.39%.Afterwards,the TiO₂ mesoporous layer with different thickness(Mo⁵⁺content is 0.1%)is successfully prepared.Conclusively,with the increase of the thickness of the mesoporous layer of TiO₂,the photoelectrical properties of DSSCs increase first and then decrease.When the mesoporous layer thickness of 10μm to 15μm,the photoelectric conversion efficiency has not changed much,but Mo⁵⁺doped TiO₂nanocrystalline film will appear the phenomenon of agglomeration and agglomeration with the increase of the thickness.Consequently,the photoelectric performance of DSSCs will be weakened.