Polythiophene-sensitized TiO2 solar cells

Polythiophene-sensitized, nanocrystalline TiO2-based photoelectrochemical cells were fabricated either by using poly(3-thiophene acetic acid) (P3TAA) or a co-polymer; poly(3-thiophene acetic acid)–poly(hexyl thiophene) (P3TAA-PHT) polymers and their performances were examined. The photocells were able to generate reasonably high photocurrent, which increases in the presence of the electron-donating ionic liquids in the electrolyte composed of redox couple I3−/I−. Dramatic enhancements in the cell performances were observed with the addition of ionic liquid 1-methyl-3-n-hexylimidazolium iodide into the electrolyte. While the cell sensitized with P3TAA generated a short-circuit photocurrent of ∼9.75 mA cm−2, an open-circuit photovoltage of ∼405 mV and a total power conversion efficiency of ∼2.4% under simulated full sunlight of 100 mW cm−2 (air mass 1.5) the cell sensitized with copolymer P3TAA-PHT delivered ∼1.6% efficiency under the same conditions with ∼7 mA cm−2 as photocurrent and ∼375 mV as photovoltage. The corresponding incident photon-to-current conversion efficiencies (IPCE) of the above cells were ∼60 and ∼40%, respectively.