Voltage-enhancement mechanisms of an organic dye in high open-circuit voltage solid-state dye-sensitized solar cells

摘要

Sensitization of solid-state dye-sensitized solar cells (SSDSSCs) with a new, organic donor-π-acceptor dye with a large molar absorption coefficient led to an open-circuit voltage of over 1 V at AM1.5 solar irradiance (100 mW/cm~2). Recombination of electrons in the TiO_2 film with the oxidized species in the hole-transfer material (HTM) was significantly slower with the organic dye than with a standard ruthenium complex dye. Density functional theory indicated that steric shielding of the electrons in the TiO_2 by the organic dye was important in reducing recombination. Preventing the loss of photoelectrons resulted in a significant voltage gain. There was no evidence that the organic dye contributed to the high voltage by shifting the band edges to more negative electrode potentials. Compared with an iodide-based liquid electrolyte, however, the more positive redox potential of the solid-state HTM used in the SSDSSCs favored higher voltages.