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Fabrication of Conductive Textile Fabric using Graphene Nanosheets and its use in Dye Sensitized Solar Cells

Fabrication of Conductive Textile Fabric using Graphene Nanosheets and its use in Dye Sensitized Solar Cells
Professor Sung Hoon Jeong
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This thesis is focused on the fabrication of conductive textile fabric by using graphene nenosheets (GNs), via a simple and quick dip and dry method, well-know to textile industry and an effort to replace expensive and rare Platinium (Pt) material used at the counter electrode (CE) in a dye sensitized solar cell (DSSC). The aim of this work was to fabricate a light weight, flexible and conductive fabric, based on a composite of cotton fabric and GNs, which can be used as a CE in DSSCs. Initially a low cost, lightweight, Pt and metal-free, flexible, GNs coated cotton fabric (GCF) was prepared and used as textile structured counter electrode (CE) in a DSSC. This novel natural fiber-based fabric electrode resulted in a low surface resistance of 114 Ωsq-1 with excellent flexibility under different bending angles and showed commendable photovoltaic conversion efficiency (PCE) of 2.52 %. This counter electrode offers advantages of not only saving the cost of Pt itself but also reducing the energy required to activate Pt at high temperature. Being flexible and light weight, this electrode can be used in a variety of applications, including wearable types of DSSCs. Further, surface conductivity and photo catalytic activity (PCA) of standard cotton fabric (SCF) were enhanced by modifying the surface charge of standard cotton fabric, from negative to positive, with a cationic agent, to convert it into cationized cotton fabric (CCF). Then, both types of fabrics were dip coated with a simple dip and dry technique for the adsorption of negatively charged graphene oxide nanosheets (GONs) onto fabric surface. This resulted in 67.74 % higher loading amount of GONs on the CCF making self-assembly. Finally, this coating was chemically converted by vapor reduction using hydrazine hydrate to reduced GNs, the resulted fabric was termed as HC-GCF. The results revealed that with such high loading of GONs, the surface resistance of CCF was only 7 Ωsq-1 as compared to 114 Ωsq-1 of the SCF and a 66 % higher PCA was also achieved through cationization for higher GONs coating. Finally, the HC-GCF was used as a highly efficient counter electrode (CE) in DSSC, as a replacement of commonly used Pt. Cyclic voltammogram, Nyquist and the Tafel plots suggest an excellent electro catalytic activity (ECA) for the reduction of tri-iodide (I_3^-) ions at the CE surface. Symmetrical cells prepared using HC-GCF, indicated a very low charge transfer resistance (RCT), of only 1.2 Ω, which was nearly same to that of Pt with 1.04 Ω. Furthermore, a high photovoltaic conversion efficiency (PCE) of 6.93 % was achieved using HC-GCF counter electrode using polymer electrolyte.
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