Study On The Morphologies Of Self-assembled Mesoporous Silica And Its Photovoltaic Application

The advantageous structure characteristics of self-assembled mesoporous SiO2, such as high BET surface area, ordered pore channels, and controllable mesophases and structural parameters in the nanometer range, has provided potential applications in a wide range of field e.g., solar cell, photocatalyst, chemical sensor, etc.The research in this thesis presented a novel approach of synthesizing mesoporous silica particles in a very dilute surfactant system where the micro-morphology and micro-structure of silica particles can be tuned by adjusting the concentration of the reactants and adding various types of co-solvent components. Furthermore the mono-dispersed nano-sized mesoporous silica particles and bicontinuous hierarchical mesoporous silica (BCMS) obtained was added into liquid electrolytes as gelator to form composite gel electrolytes for the application in the dye-sensitized solar cells and lithium battery. The main content and results are presented below.In a very dilute surfactant system, mono-dispersed nano-sized (10~100nm) mesoporous silica particles were synthesized via self-assembly approach. By regulating the reagent concentration, the sizes and morphology (monodisperse particles or the network structure) of the synthesized particles can be controlled over a relatively wide range. The synthesized particles have high surface area and thermal stability. The formation of the nano-sized mesoporous silica particles was proposed to be correlated with the self-assembly reaction between silicate oligomers and surfactant.In the water/oil two-phase system, the morphology and structure of silica particles were classified and investigated systematically, which facilitated the understanding of silica morphosynthesis in the applied system. The relationship between the morphogenesis and reaction conditions was discussed in both water/diethyl ether and water/ethanol systems. A mechanism of morphology formation was proposed. It was suggested that an intrinsic uncertainty factor occurs in the OWTP system. The results indicate that, the evolution of critical packing parameter g and the non-equilibrium interfaces formed by fluid rheological distortions and reconstructive reaction fields played a crucial role in the morph-synthesis process.In the water/diethyl ether system, novel bicontinuous hierarchical mesoporous silica was synthesized with the block copolymer F127 as surfactant. Compared with the traditional nanoparticles or mesoporous silica, BCMS had a unique hierarchical pore structure. It was incorporated into composited gel electrolytes for dye-sensitized solar cells and lithium battery application. The results showed that the quasi-solid state electrolyte has conductivity as 10-3S·cm-1 and good mechanical stability.As inorganic gelators, the nano-sized silica particles were added into the electrolyte of dye-sensitized solar cells. The effects of the size and structure of the particles added were discussed with respect to the electrochemical properties of the electrolyte. A simplified simulation was processed in explaining the improved conductivity. After the introduction of the mesoporous silica particles, the I—3 ion diffusion coefficients and the exchange current density I0 were promoted along with the increase of the photocurrent density and reduction in the dark reaction. Compared to those without mesoporous silica particles, the photo-conversion efficiency of the quasi-solid state DSSC processed in the presented approach was enhanced by 44%.