Electrostatic adsorption of a fluorophores-modified light-harvesting complex II on TiO2 photoanodes enhances photovoltaic performance

Abstract The major light-harvesting complex of photosystem II, or LHCII, has been utilized in photovoltaic applications because of its high pigment density. In vitro assembled recombinant LHCII is a modifiable biomimetic material for solar energy conversion. In this report, we assemble a modified recombinant LHCII from apoproteins covalently conjugated artificial fluorophores Atto 590 which absorb greatly near visible green region, where LHCII possesses relatively weak absorption. The absorption and fluorescence excitation spectra indicate that the modified recombinant LHCII possesses enhanced light harvesting capacity because Atto 590 molecules efficiently transfer energy to LHCII. The unmodified or modified recombinant LHCII is then adsorbed on the TiO2 electrode respectively to construct sensitized solar cells, both of which present remarkable photovoltaic enhancement. The incident photon-to-electron conversion efficiency measurements confirm the contribution of the artificial fluorophores. The modified recombinant LHCII sensitized solar cell presents 9.1% increase in open circuit voltage and 13.6% increase in short-circuit current density, compared to the unmodified one. These results suggest that modifications of the recombinant LHCII are feasible ways to enhance its performance in biophotovoltaic cells.