Efficiency enhancement in dye sensitized solar cells through step wise cosensitization of TiO2 electrode with N719 and metal free dye

We have used a step-wise cosensitization process to improve the power conversion efficiency (PCE) of dye sensitized solar cells employing N719 and metal free dye TA-St-CA. The DSSC sensitized with N719/TA-St-CA shows a PCE of 8.27% which is higher than for the DSSCs sensitized with either N719 (5.78 %) or TA-St-CA (4.45%). The improved PCE is attributed to the enhanced overall dye loading as well the reduced dye aggregation that has resulted from the usage of dyes with different anchoring units. The enhancement in the PCE has also been attributed to increase in both short circuit photocurrent and open circuit voltage. This was due to the reduced dark current and suppression of back recombination of injected electrons in the conduction band of TiO2 photoanode with the I3- ions in the electrolyte.