Mohd Hamdi, Ali@Buraidah (2012) Ionic conductivity and related studies on chitosan-based electrolytes with application in solar cells / Mohd Hamdi Ali@Buraidah. PhD thesis, University of Malaya.
Abstract
The motivation in this work is to ensure that the chitosan biopolymer can be used as a host for ion conduction and used as an electrolyte in dye-sensitized solar cells (DSSCs). The conductivity of the chitosan-NH4I electrolytes was optimized by varying the NH4I concentration, blending chitosan with PVA and PEO and also by incorporating of ionic liquid (IL). The electrolytes were prepared by solution cast technique. FTIR results confirm complexation between polymer, NH4I and IL. Hydrogen bonding between chitosan and PVA and between chitosan and PEO are observed in the respective spectrum. XRD indicates that the amorphousness of pure chitosan, chitosan-PVA and chitosan-PEO films changes with NH4I concentration. The 55 wt.% chitosan-45 wt.% NH4I (Ch9) sample exhibits the highest room temperature conductivity of 3.73 × 10-7 S cm-1. Blending chitosan with PVA and PEO further increased conductivity. The 27.5 wt.% chitosan-27.5 wt.% PVA-45 wt.% NH4I (CV5) sample exhibits the highest conductivity of 1.77 × 10-7 S cm-1 at room temperature and the highest conducting sample in (chitosan-PEO)-NH4I system is 3.66 × 10-6 S cm-1 for sample containing 16.5 wt.% chitosan-38.5 wt.% PEO-45 wt.% NH4I (CEO7) electrolyte. Incorporating 50 wt.% IL into Ch9, the electrolyte CIL5 exhibits the highest room temperature conductivity of 3.43 × 10-5 S cm-1. The activation energy, EA for the highest conducting samples follows the order Ch9 (0.45 eV) < CV5 (0.38 eV) < CEO7 (0.31 eV) < CIL5 (0.25 eV). DSSCs were fabricated using natural dyes extracted from black rice, blueberry and red cabbage. The highest conducting samples from each system have been chosen in the fabrication DSSCs. Some iodine crystals were added to the electrolytes to produce the redox-mediator. Red cabbage DSSCs using CIL5(+I2) gel electrolyte exhibits the highest efficiency of 0.2 % compared to using CEO7(+I2) and CV5(+I2) gel electrolytes.
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