Effect of iodine concentration on the photovoltaic properties of dye sensitized solar cells for various I2/LiI ratios

In the present study, the effect of iodine concentration on the photovoltaic properties of dye sensitized solar cells (DSSC) based on TiO2 nanoparticles for three different ratios of lithium iodide (LiI) and iodine (I2) has been investigated. The electron transport properties and interfacial recombination kinetics have been evaluated by electrochemical impedance spectroscopy (EIS). It is found that increasing the concentration of lithium iodide for all ratios of iodine and lithium iodide decreases the open-circuit voltage (Voc) whereas short circuit current density (Jsc) and fill factor (FF) shows improvement. The reduction in Voc and increment in Jsc is ascribed to the higher concentration of absorptive Li+ cations which shifts the conduction band edge of TiO2 positively. The increase in FF is due to the reduction in electron transport resistance (Rω) of the cell. In addition for all the ratios of LiI/I2 increasing the concentration of I2 decreases the Voc which is attributed to the increased recombination with tri-iodide ions (I3−) as verified from the low recombination resistance (Rk) and electron lifetime (τ) values obtained by EIS analysis.

► Effect of lithium iodide and iodine ratio on dye solar cell performance.
► Study of electron transport properties by electrochemical impedance spectroscopy.
► Evaluation of electron diffusion coefficient and life time.