Effect of chenodeoxycholic acid (CDCA) additive on phenothiazine dyes sensitized photovoltaic performance

The effects of chenodeoxycholic acid (CDCA) in a dye solution as a co-adsorbent on the photovoltaic performance of dye-sensitized solar cells (DSSCs) based on two organic dyes containing phenothiazine and triarylamine segments (P1 and P2) were investigated. It was found that the coadsorption of CDCA can hinder the formation of dye aggregates and improve electron injection yield and thus J (sc). This has also led to a rise in photovoltage, which is attributed to the decrease of charge recombination. The DSSC based on dye P2 showed better photovoltaic performance than P1: a maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 89.5%, a short-circuit photocurrent density (J (sc)) of 9.57 mA/cm(2), an open-circuit photovoltage (V (oc)) of 697 mV, and a fill factor (FF) of 0.66, corresponding to an overall conversion efficiency of 4.42% under the standard global AM 1.5 solar light condition. The overall conversion efficiency was further improved to 5.31% (J (sc) = 10.36 mA/cm(2), V (oc) = 0.730 V, FF = 0.70) upon addition of 10 mM CDCA to the dye solution for TiO2 sensitization. Electrochemical impedance data indicate that the electron lifetime was improved by coadsorption of CDCA, accounting for the significant improvement of V (oc). These results suggest that interfacial engineering of the organic dye-sensitized TiO2 electrodes is important for highly efficient photovoltaic performance of the solar cell.