Dye-sensitized Solar Cells Based On TiO₂ Hierarchical Networks/nanoparticles Double-layer Film Photoanodes

Dye-sensitized solar cells（DSSCs）,as a typical representative of new solar cells,have been widely studied in the photovoltaic field due to their simple process,wide source of raw materials,and environmental friendliness.Ti O₂ nanoparticle films have been widely used in DSSCs and achieved a certain photoelectric conversion efficiency（PCE）,but they still have the disadvantages of low visible light utilization rate and high electron recombination rate.In this paper,a facile one-step hydrothermal method was used to prepare a novel Ti O₂ hierarchical networks/nanoparticles（THN/NP）double-layer film photoanode,and the effect of hydrothermal time on its growth was studied in detail.The structure,morphology,and crystal identity of the photoanode were systematically characterized by test methods such as SEM,TEM,and XRD.At the same time,the optical and electrochemical properties of photoanodes were studied using ultraviolet-visible spectroscopy（UV-vis）and electrochemical impedance spectroscopy（EIS）.The results show that the THN/NP photoanode has suitable dye loading,excellent light scattering ability and efficient electron transfer paths.DSSCs constructed with THN/NP photoanodes have excellent photovoltaic performance.The PCE is 5.49%,which is an improvement of 9.1%compared to DSSCs constructed with P25photoanodes.In order to further improve the PCE of DSSCs,Au nanoparticles with an averagediameter of 20 nm were prepared by the sodium citrate reduction method.THN/NP photoanodes were immersed in Au nanoparticle solutions with different concentrations for modification,in order to enhance the visible light absorption capability of the photoanode by localized surface plasmon resonance（LSPR）effect of the Au nanoparticles.The results show that when the mass percentage of Au nanoparticles embedded in the THN/NP photoanode is about 1wt%,DSSCs constructed with Au-THN/NP photoanodes achieved the best PCE（5.97%）,which is increased by 18.7%compared to DSSCs constructed with P25 photoanodes.