Efficient dye-sensitized solar cells based on cosensitized metal free organic dyes with complementary absorption spectra

Dye sensitized solar cells (DSSCs) were fabricated using two metal-free organic dyes, TA-St-CA and D, with complementary absorption bands in the visible and near infrared regions. The power conversion efficiency (PCE) of the cosensitized DSSC (6.26%) was improved when compared to DSSCs based on individual dyes TA-St-CA (4.98%) or D (4.22%). The PCE was further enhanced up to 7.19% when deoxycholic acid (DCA) was added to the mixed dye solution as a coadsorbant. The enhancement of PCE observed in the cosensitized DSSC by addition of DCA was attributed to both suppression of dye aggregation and prevention of the backward electron transfer from the conduction band of TiO2.