Fabrication and photovoltaic characterization of bio-sensitized solar cells using myoglobin-based sensitizers

Myoglobin (Mb), reconstituted zinc protoporphyrin-apomyoglobin (ZnMb), and eosin-modified ZnMb (EoZnMb) were used as photosensitizers to functionalize TiO2 nanocrystalline films for bio-sensitized solar-cell (BSSC) applications. For the Mb-sensitized SC, the poor cell performance was due to a reduction Fe(III) --> Fe(II) that produces a photocurrent density of the device smaller than its unsensitized counterpart. The efficiencies of power conversion of both ZnMb and EoZnMb-sensitized SC were enhanced about ten times due to superior charge separation between TiO2 and the protein, and due to smaller current leakage between TiO2 and the electrolyte. The cell performances of the BSSC devices are discussed in terms of an equivalent-circuit model.