Aggregation property and photovoltaic performance optimization of symmetrical squaraine dye containing bis-anchoring groups for dye-sensitized solar cell

The effect of chenodeoxycholic acid (CDCA) used as the coadsorbent with a symmetrical squaraine (SSQ) sensitizer on TiO2-based solar cells was investigated, and it was found that the coadsorbent retards the SSQ sensitizer from aggregating on the TiO2 photoanode but diminishes dye amount leading to an interdependent solar cell performance. Analysis of the optical spectra and incident photon-to-current conversion efficiency data revealed that the amount of SSQ sensitizer as well as the presence of aggregates is significantly dependent on the molar concentration of CDCA coadsorbent. In addition, electrochemical impedance and stepped light-induced transient measurements of photocurrent and voltage measurements are also used to explain and support the behavior of the co-sensitized solar cells. The short-circuit current density and open circuit voltage of the devices with CDCA increases due to the decreased charge transfer resistance, enhanced diffusion length and electron lifetime in the mesoporous TiO2 photo electrode.