Investigating the Role of Dye Dipole on Open Circuit Voltage in Solid-State Dye-Sensitized Solar Cells

Abstract

To eliminate the possibility of perturbation caused by a liquid electrolyte and predict the role played by the nature of dipole of sensitizers with respect to the observed open circuit voltage (Voc) in dye-sensitized solar cells (DSSCs) more precisely, solid-state DSSCs were fabricated using different sensitizing dyes. Results obtained by surface potential measurement indicate that increasing the alkyl chain length in symmetrical squaraine dyes leads to a relatively positive shift in surface potential. The use of dyes exhibiting higher surface potentials leads to the observation of increased Voc, which has been explained by the dye dipole formation at the TiO2/hole transporting layer interface leading to an upward shift of the TiO2 conduction band. It is thus possible to obtain a high Voc in DSSCs by designing new dyes either having long alkyl chains or a molecular structure having a higher dipole moment exhibiting a relatively positive shift in surface potential.