Investigation of Preparation and Properties of Ordered Porous TiO2
|School||Changsha University of Science and Technology|
|Keywords||polystyrene ordered porous TiO2 colloidal crystal templates Gd-doped dye-sensitized solar cells|
In recent years, the increasing serius environment pollution and energy crisis prompt the rapid development of solar energy. And considerable attention has been given to dye-sensitized solar cells （DSSCs） in the field of green energy sources because of its simple process and low cost. However, the specific surface area of nano TiO2 materials is low while the electron-hole recombination rate is high in disordered structures, which lead to a low photoelectrical conversion. Therefore, a lot of studies on ordered porous TiO2 materials bave been recently carried out. And colloidal crystal templates have been the most effective to synthesis ordered porous materials with controlled pore size and homogenous pore size distribution, which has caused the extensive concern in science and technology.In this work, ordered porous TiO2 were fabricated through sol-gel method using colloid polystyrene colloidal crystals as templates. The DSSCs were fabricated to study the photoelectrical properties of ordered porous TiO2. In addition, the ordered porous TiO2 were modified by Gd doping. The main rearch work and results were as following.Monodisperse polystyrene microspheres with even particles size were prepared by emulsion polymerization. The effect of polymerization time and initiator concentration on the particles size were studied, the aim is to use polystyrene microspheres with different particles size as templates to fabricate porous materials with different pore size. And the particles size decreased when increased the initiator concentration and decreased the polymerization time.High quality polystyrene colloidal crystals templates with different particles could be fabricated on conductive glass by dip-drawing method. The results indicated that the essential factors are the concentration of microspheres in emulsion and the drawing rate of conductive glass. For particles of 300nm in diameter, the volume fraction of 20vol%, and 3cm/min, respectively, monolayer colloidal crystal templates were fabricated. For particles of 390nm in diameter, the volume fraction of 20vol%, and 1cm/min, respectively, three dimensional colloidal crystal templates were fabricated.The TiO2 materials prepared by polystyrene colloidal crystal templates were neat, highly ordered. The effects of polystyrene colloidal crystal templates, concentration of TiO2 sol and immersion time of templates in TiO2 sol on the microstructure of TiO2 materials were studied. The preferable conditions of the ordered porous TiO2 are as follows. The optimum aging time of TiO2 sol was 12h, and immersion time was 3min when used the monolayer PS templates, and the immersion time should increased to 5min once the multilayer PS templates were used.Finally, Gd-doped ordered porous TiO2 which were used to fabricate dye-sensitized solar cells were prepared by the optimized process condition. And the effect of the microstructure of TiO2 and Gd doped on the properties of dye-sensitized solar cells were studied. The results indicated that the light absorption properties of TiO2 had been inhanced after doped with 0.5wt% Gd3+ which was benefial to increases the photoelectrical conversion. And it demonstrated that the multilayer porous TiO2 could enhance the photoelectrical properties. The DSSCs based on multilayer porous TiO2 films doped with 0.5wt% Gd3+ exhibited a high conversion efficiency （η） of 1.6% with short circuit current （Jsc） of 4.13 mA·cm-2 and open circuit （Voc） of 0.68 V.