Performance investigation of organic dye sensitezed solar cell by using electrochemi̇cal impedans spectroscopy

In this work, we studied the electrochemical characteristics of dye-sensitized solar cells using an ionic liquid as the electrolyte and we compared them with the response of a solvent –containing electrolyte cell. Impedance spectroscopy is useful technique for determining important cell parameters such as recombination resistance, chemical capacitance and diffusion parameters for dye-sensitized solar cell. Volatility of the solvents employed is important issue for long term device performance. Solid or nonvolatility phase electrolyte is alternative for organic solvent containing electrolyte. Room temperature ionic liquids (RTIL's) have high ionic conductivity and high thermal stability. These properties make them useful for dye sensitized solar cells applications. Initially, for the measurements, our cells have been prepared with 0.6 M Iodide ionic liquid, 0.1 M LiI (Lithium iodide), 0.05 M I2 and 0.5 M TBP (4-tert-butylpyridine) as an electrolyte solvent MPN (3-methoxypropionitrile). Our room temperature ionic liquids were AMEII, AEII, AMII and PMII has been used as a reference. For determining diffusion parameters, two electrode sandwich cells have been prepared. Subsequently diffusion coefficients of ionic liquids and electron lifetime of dye-sensitized solar cell have been characterized. For fitting experimental curves with our model's curves impedance analyzer has been used. The impedance curves have been fitted with suitable models. Our models include Warburg diffusion parameters and double layer capacitance. Consequently, reference electrolyte AEII and PMII gave a diffusion coefficiency with a rate of 1.7538E-7 cm2s-1 and 2.0572E-7 cm2s-1. This result showed that AMEII could be an alternative material for dye-sensitized solar cells containing ionic liquid as an electrolyte. In the last part of thesis, impedance analyses of DSSCs at different temperatures have been demonstrated. With increasing temperature, electron density is increasing though recombination become dominate for cells. It was observed that in order to increase the DSSC performance, the recombination mechanism must be controled. Finally at different temperature, parameters which are so important for DSSC performance, such as difusion coefficent, electron lifetime, chemical potential, charge trasnfer resistance have been calculated with EIS.