A core-shell approach that utilizes a high-surface-area conducting core and an outer semiconductor shell is exploited here to prepare p-type dye-sensitized solar energy cells that operate with a minimal applied bias. Photocathodes were prepared by coating thin films of nanocrystalline indium tin oxide with a 0.8 nm Al2O3 seeding layer, followed by the chemical growth of nonstoichiometric strontium titanate. Films were annealed and sensitized with either a porphyrin chromophore or a chromophore-catalyst molecular assembly consisting of the porphyrin covalently tethered to the ruthenium complex. The sensitized photoelectrodes produced cathodic photocurrents of up to -315 μA/cm2 under simulated sunlight (AM1.5G, 100 mW/cm2) in aqueous media, pH 5. The photocurrent was increased by the addition of regenerative hole donors to the system, consistent with slow interfacial recombination kinetics, an important property of p-type dye-sensitized electrodes.
Keywords: artificial photosynthesis; core−shell; dye-sensitized photoelectrosynthesis cell; hole transfer; photocathodes; strontium titanate.