Improvement Of Photon Capture Efficiency And Performance Of TiO₂ Photoanode

As a new type of solar cell,dye-sensitized solar cells have attracted worldwide attention due to the increasingly serious environmental pollution and energy crisis.DSSCs have great development potential and good application prospects because of its many advantages such as wide source of raw materials,low cost and simple preparation process.DSSCs are generally composed of a dye-sensitized photoanode,an electrolyte and a counter electrode.Photoanode,as one of the most important component of DSSCs,plays an important role in the adsorption of dye molecules and the transport of electrons.Therefore,more and more researchers are working to improve the photoanode of DSSCs.Compared to other photoanode materials?SnO₂ and ZnO?,TiO₂ are the most promising candidates because of its many irreplaceable advantages.At present,TiO₂photoanodes have some defects such as low utilization efficiency of incident light.This defect greatly reduces the photoelectric conversion efficiency?PCE?of the battery.Therefore,this paper focuses on how to improve the photoanode material and structure of DSSCs to improve the photon capture efficiency of TiO₂ photoanodes and the PCE.The research content of this work is divided into the following four parts:?1?A micron-sized urchin-like TiO₂ material was synthesized by hydrothermal method.Then a double-layer photoanode?named UTP?was fabricated by using P25 as the electron transport layer and urchin-like TiO₂ as the light-scattering layer.The light-scattering layer exhibited excellent light scattering ability,increased the propagation of the incident light,and improved the photon capture efficiency of the photoanode.Compared with the single-layer P25 DSSCs,the short-circuit current of the UTP DSSCs were significantly improved,and the PCE was increased to 6.14%.?2?A kind of Ag/P25 composite was synthesized by a simple method.DSSCs fabricated by Ag/P25 composites?named M-Ag cells?were capable of adsorbing more dye molecules,had better catalytic effects,and exhibited better photon capture capability due to local surface plasmon resonance?LSPR?effects.As a result,the best M-Ag DSSCs achieved a PCE of 7.09%,indicating a¹9.1%enhancement compared with that of the pure P25 DSSCs.However,the excess and agglomerated Ag nanoparticles in the Ag/P25 composite will become a recombination center to accelerate photoelectron recombination.?3?A simple method for placing a thin layer of Ag nanoparticles between an FTO and photoanode film was designed.It was found that the photoanode improved the photon trapping efficiency due to the Mie scattering effect of the Ag nanoparticles and improved the charge transfer characteristics of the interface.The PCE of DSSCs fabricated by the photoanode?named Ag-L?reached 6.97%.Similarly,when the Ag nanoparticles are excessive,they will become carrier recombination centers,reducing the lifetime of electrons.?4?A detailed comparison of the above two methods for improving the photon capture rate of DSSCs by using Ag nanoparticles has been made.It was found that since the Ag nanoparticles were randomly distributed in the M-Ag photoanode,the M-Ag DSSCs obtained the best light absorption capability by the LSPR effect.However,the Ag-L DSSCs had a higher short-circuit current than the M-Ag DSSCs due to its better interface charge transfer capability.But in both ways,it can be seen that Ag nanoparticles that are in direct contact with the dye and electrolyte will become composite centers,which will reduce electron lifetime and electron collection efficiency.