Synthesis of Polymeric Dispersants for Nanomaterials and Dye-Sensitized Solar Cells

“Dispersion technology” is considered as the key step in bottom-up process for self-assemblies and fabricating nanomaterial devices. Herein, dispersion of sp2 carbon materials, graphene and carbon nanotube (CNT), in aqueous or organic mediums is important process for utilizing nanomaterials in various downstream applications. Further, the performance of adding CNT and 2D platelet-like graphene as the nanoscale fillers to nanocomposites relies on the step of homogeneously dispersing the nanomaterials into their primary structure. Nanohybrids including silver nanoparticles decorated on the carbon nanotube (CNT) and platinum-on-graphene were fabricated by ionic excharge reaction and non-covalent method. These materials were investigated on dispersibility, particle size and distribution, electrical behavior, and the applications for dye-sensitized solar cells (DSSCs). There are two parts in this dissertation, aiming to investigate the dispersion of nanomaterials including nanoparticles such as silver nanoparticle (AgNP), titanium dioxide and platinum nanoparticle (PtNP), carbon materials such as carbon nanotube (CNT) and graphene and the sequential hybridization for the use in DSSCs. In the first part, two families of functional polymers for homogeneously dispersing CNT and graphene in aqueous medium were reported. The tandem procedures of dispersing CNT and then AgNPs were developed to prepare CNT-tethered AgNPs nanohybrids, which allowed the conductive application at low temperature (Chapter 3); the structural differences in chemical functionalities of the synthesized polymers were allowed to evaluate their ability for dispersing graphene by disrupting the π-π stacking aggregation. With the assistance of adding polyvinyl alcohol, the homogeneously dispersed graphene in water was fabricated into a dimensionally stable film exhibiting high conductivity, evidenced the dispersing ability of the synthesized oligomers as the polymeric dispersants. With the introduction of waterborne polyurethane, conductive and flexible graphene films were prepared. In addition, by utilizing the dispersing mechanism of graphene, graphene directly exfoliated from graphite was realized, and that prevents the inevitable structural defects and lowers the cost of graphene preparation (Chapter 4). In the second part, dispersion of nanomaterials applied on DSSCs was exploited to assess the dispersibility and the importance of dispersion. The dispersion of TiO2 nanoparticles to generate the functional films effectively allows the control of TiO2 particle size and pore size distribution in film matrix for suitable uses as photoanodes in DSSCs (Chapter 5). A dispersion of platinum-on-graphene was prepared in the presence of a polymeric dispersant and subsequent in-situ reduction of dihydrogen hexachloroplatinate to metallic platinum on the graphene surface. The platinum-on-graphene dispersion was coated on an FTO glass to prepare a counter electrode (CE) for a DSSC. The hybrid film of platinum nanoparticles and graphene nanoplatelets (PtNP/GN) showed a transparency of 70% at 550 nm, indicating its suitability as a CE material for a rear-illuminated DSSC (Chapter 6).