Natural hybrid organic-inorganic photovoltaic devices

Natural hybrid organic-inorganic photovoltaic devices based on TiO2 have been realized. Chlorophyll A (from anacystis nidulans algae), chlorophyll B (from spinach), carmic acid (from insect Coccus cacti L.), synthetic trans-beta-carotene, natural fresh picked Morus nigra, and their mixtures have been used as an organic photo active layer to fabricate photovoltaic prototypes. In order to reduce the charge's interfacial recombination, different thicknesses (5-45 nm) of Si layers, subsequently oxidized in air, were inserted between the TiO2 and chlorophyll B. Scanning electron microscopy of TiO2 and Si/TiO2 systems shows the coexistence at least of four classes of nanoparticles of 60, 100, 150 and 250 nm in size. Auger electron spectroscopy of the Si L2,3VV transition demonstrates the presence, of silica and SiOx suboxides. Photocurrent measurements versus radiation wavelength in the range 300-800 nm exhibit different peaks according to the absorption spectra of the organic molecules. All realized photovoltaic devices are suitable for solar light electric energy conversion. Those made of a blend of all organic molecules achieved higher current and voltage output. The Si/TiO2-based devices containing chlorophyll B exhibited an enhanced photocurrent response with respect to those with TiO2 only. (C) 2009 Elsevier Ltd. All rights reserved.