Fabrication of Carbon Mesoporous Materials for Potential Application as Counter Electrode for Quasi-solid Stated Dye Sensitized Solar Cells

Abstract

The dissertation focuses on the synthesis of porous defect rich carbon nanomaterial suitable for quasi-solid state dye sensitized solar cells. Multi-walled carbon nanotubes (MWCNT) play an important role in the field of solar cell technology. Carbon nanotubes owing to higher conductivity and good electro catalytic activity is a potential candidate for the counter electrode material in quasi-solid state dye sensitized solar cells. The focus of this research was to functionalize carbon nanotubes to produce surface defects on the tubular surface of contend to intact the sp2 hybridized C-C configuration. Different approaches in the synthesis of defects on MWCNT by chemical vapor deposition, acid functionalization, or nitrogen doping. These techniques somehow disturbed the sp2 covalent bonding configuration and affected the electronic conductivity of MWCNT. Herein, we proposed a facile method to create defects on the peripheral of MWCNT by mild acid treatment, followed by filling porous charcoal or metal nanomaterials to intact its conjugated bond structure and enhance its electro catalytic activity. The focus was based on to decay a basal plane morphology of MWCNT and fill a porous carbon or metal in the lattice of nanotube layer by means of ultrasonic assisted covalent functionalization method. The fundamental approach would be the generation of vacant trapping centers in the tubular graphitic network, and fill the trapping centers with porous carbon atoms or metal atoms to generate catalytic sites. Foreign atoms occupying vacancies in MWCNT would be of particular interest in the context of doping. The mechanisms of trapping and de-trapping of defects as well as the mobility of substitutional atoms are subjects that have to be understood if the electrical properties of MWCNT materials are to be modified. Moreover, the research scheme includes the usage of various textile fabrics to produce low cost and flexible electrodes as a replacement of brittle and highly expensive FTO glass. The aim of this research is to study the effect of morphology and absorbance of various textile fabrics on the overall performance of quasi-solid state dye-sensitized solar cells by using natural and synthetic textile fabrics. The hypothesis also includes the utilization of high viscosity gel electrolyte to solve the problem of leakage and evaporation of liquid electrolyte. For this purpose, following research objectives were taken to synthesize our proposed system of electrode materials. a) Synthesis and fabrication of defect rich MWCNT termed as functionalized mesoporous carbon (f-MC) material by using activated charcoal doping. b) Electro catalytic activity, photocatalytic activity, electrochemical and photovoltaic performance of proposed porous vacancy MWCNT nanomaterial fabricated on FTO and different fabric substrates were investigated. c) Synthesis and fabrication of metal doped MWCNT termed as carbon metallic heterostructure composite (CMHC) based on generating defects and trapping metal bismuth sulfide in the lattice of MWCNT. d) The proposed CMHC nanomaterial were used as conductive and photocatalytic active flexible electrode by using fabric substrate. This thesis will give an insight to address the problems with the Pt based DSSC and suggest alternate composite materials that are low in cost and render comparable efficiency with gel electrolyte. Therefore, the collective strategy of developing carbon based composites with the addition of porous materials, coating these carbon composites on various textile fabrics to develop flexible and efficient CE and using gel electrolyte to produce a quasi-solid state dye sensitized solar cell, opens a route for the production of low cost DSSC.