Electrochemical Impedance Spectroscopy Analysis to Find the Effect of Compression Temperature on the Performance of P25 Based Dye-sensitized Solar Cell

In this investigation the effect of varying compression temperature on photovoltaic performance for $\mathrm{T}\mathrm{i}\mathrm{O}_{2}$-based Dye-sensitized-solar-cell (DSSC) has been observed using electrochemical impedance spectroscopy (EIS) analysis. The cells are fabricated using a new electrophoretic deposition technique that is four-layer-four-side electrophoretic deposition which ensures homogenous crack free photo electrode surface. Electrodeposited photoanodes are compressed by changing compression temperature (from 25°C to 90°C) as an post deposition treatment. From the impedance spectroscopy analysis the changes of impedance in Nyquist plot $\mathrm{z}^{\prime}\mathrm{v}\mathrm{s}. \mathrm{z}^{\prime\prime}$ shows that due to changes in compression temperature (25°C to 90 $0_{\mathrm{C})}$ the values of charge transfer resistance $\mathrm{R}_{\mathrm{c}\mathrm{t}}(\mathrm{A}\mathrm{E})$ are reduced and that's why more electrons are found to be conducted inside the film. Bode plot shows that shifting of charge transport's characteristics frequency peak $\mathrm{F}_{\max}$ towards low frequency increases the value of electron life time ($\tau$) which has been observed by increasing the compression temperature upto 70°C. Since open circuit voltage $\mathrm{V}_{\mathrm{o}\mathrm{c}}$ is proportional to electron life time ($\tau$), the increasing value of electron life time ($\tau$) causes the value of open circuit voltage $\mathrm{V}_{\mathrm{o}\mathrm{c}}$ to be increased by increasing the temperature in compression upto 70°C. The Fill Factor (FF) has been improved due to the uniformity of layers by varying the compression temperature upto 70°C. Series resistance $(\mathrm{R}_{\mathrm{s}})$ of the cell from EIS data reduces up to 70°C compressed temperature which is similar to the calculated series resistance from I-V curve. Value of shunt resistance $(\mathrm{R}_{\mathrm{s}\mathrm{h}})$ from EIS data increases with the increasing of compressed temperature upto 70°C, which matches with the calculated value of shunt resistance from I-V curve. At optimum 70°C compression temperature and 40 MPa compression pressure the maximum efficiency ($\eta$) of 3.85% has been attained which gives the open circuit voltage $\mathrm{V}_{\mathrm{o}\mathrm{c}}$, photo current density $\mathrm{J}_{\mathrm{s}\mathrm{c}}$ and Fill factor of 0.739 V, 9.30 $\mathrm{m}\mathrm{A}/\mathrm{c}\mathrm{m}^{2}$ and 0.58 respectively.