Photoanode Preparation Of The Dye-sensitized Solar Cells And Optical - Electrochemical Performance

Nano TiO2 is much significance in many fields due to its special structure, performance and excellent semiconductor photocatalytic characteristics. Therefore, more and more researcher pay attention on TiO2 as first materal of DSCs'anode. However, the disordered nano-structure, the fast recombinationrate of photogenerated electron-hole pairs in the bulk TiO2 and the low quantum yield of photochemical conwersion for solar energy hinder the application of TiO2 photochemical. In recent years, many studies show that TiO2 nanotube can improve these performances, enhance the photoelectric conversion efficiency of DSC.In the present work, we focus on the development of electrochemical anodic oxidation technique to directly fabricate highly ordered TiO2 nanotube array films onthe titanium substrate. Some preparation parameters of TiO2 nanotube arrays were systemically investigated. The SEM, XRD, Raman spectroscopy, differential thermal analysis spectrum, EIS, and photocurrent spectroscopy were performed to characterize the morphology, crystalline phase and optical-electrochemical property of TiO2 nanotube array. The heat treatment conditions on the effects of TiO2 nanotube films was discussed as well. Secondly, thin films of TiO2 nanocrystalline were fabricated by Sol-Gel method, the best reagent ratio and the optimal process were obtained by using phase diagram analysis. We analyse the differences of the photoelectric conversion efficiency of two TiO2 nano thin film assembled to the DSC. Progress and key results are as follows:(1) Thin films of TiO2 nanotube arrays were fabricated by anodic oxidation method in various fluoride electrolysis. The results show that the electrolyte solution and applied votage have a great effect on microstructure of the films. High order-aligned and smooth wall TiO2 nanotube arrays are prepared in organic electrolyte solution. In addition, the electric field intensity on the formation of TiO2 nanotubes plays a dual role, the outer diameter (d) of nanotubes is increased linearly with applied voltage (U) within a certain range.(2) Anodic oxidation process of the TiO2 nanotube array formation mechanism are divided into three stages:the first stage is the barrier layer formation stage, the current sharp decline; the second stage is the nano-tube formation stage, current is picked up; the third stage is the nanotubes stable growth stage, the current remained unchanged.(3) TiO2 nanotube films were annealed under different treatment conditions. The results show that the TiO2 nanotubes crystal structure is transformed from amorphism to anatase,then to rutile with increasing temperature. At the same time the nanotubes structure of TiO2 nanotube films gradually collapse, and finally into loose granular structure.(4) Thin films of TiO2 nanocrystalline were fabricated by Sol-Gel method. The results show that Sol-Gel preparation of nanocrystalline TiO2 films best reagent ratio is 0.2-0.8mol/L Ti(OC4H9)4, the molar ratio of chelating reagent to Ti(OC4H9)4 is 3-5. Identified the acidic precursor solution pH=3-4 and alkaline pH= 9-10, the best temperature for hydrolysis is 40-50℃.(5) The optical-electrochemical property of TiO2 nanotube array and DSC was tested. And compared photoelectric conversion efficiency of DSC by two different TiO2 nanofilms assembled. The DSC by TiO2 nanotube films assembled is not conducive to improve photoelectric conversion efficiency of DSC because of a larger loss of photon and thin film.