Photovoltaic properties of bulk heterojunction solar cells with improved spectral coverage

The potential of dye sensitization of organic solar cells has been investigated. The electrical and photoelectrical properties of such devices have been studied. The architecture of the solar cell is based on spin-coated thin films of MEH-PPV sensitized with Hydrogen Phthalocyanine (PcH2) and Coumarin 343 dyes, which are sandwiched between indium tin oxide (ITO)-coated glass and aluminium electrodes. By adding PcH2 and Coumarin 343 to the MEH-PPV active layer the width of absorption spectrum increases drastically. Introduction of a methine unit (–CHCH–) connecting the cyano (–CN) and carboxyl (–COOH) groups into the Coumarin 343 framework expanded the π — conjugated in the dye and thus resulted in a wide absorption in the visible region. The sensitization of the MEH-PPV thin film by PcH2 and Coumarin 343 dyes leads to photoluminescence (PL) enhancement whereas the incorporation of fullerene molecules (C60) in the blend, acting as electron acceptors, induces PL quenching due to the separation of the photogenerated charges. Photocurrent enhancement and increase of the open circuit voltage are induced by dye sensitization of MEH-PPV/C60 blends.