Photosensitive in wide spectral region composites based on polyphenylenevinylene

Abstract

Optical and photovoltaic properties of polyphenylenevinylene derivative – poly(2-methoxy-5-(3-,7-dimethyl-octyloxy)-1,4-phenylenevinylene (MDMO-PPV) and its composites with high (40 %) concentration polymethine dyes (PD) – meso-Cl and hexaindoletricarbocyanine (HITC) films have been studied. Two H-aggregates of dyes with different energies that weakly depend on the molecular structure of dyes, is formed in MDMO-PPV with PD in composites films. The efficiency of photogeneration of charge carrier by these aggregates is greater than the efficiency of photogeneration of charge carriers by the quasi-isolated molecules of dye. It results in substantial expansion of the absorption region (in comparison with the absorption region of molecules in solution) and photosensitivity in the side of higher energies. The presence of PD aggregates in the films MDMO-PPV influences on their photosensitivity that depends on PD molecular structure. This dependence can be caused by interaction between the molecules of MDMO-PPV and dye. In composites MDMO-PPV/HITC, the value of interaction is low and practically does not influence the efficiency of photogeneration of charge carriers by MDMO-PPV molecules, which give a considerable contribution to formation of the photovoltage in 2-3 eV regions. The interaction of meso-Cl and MDMO-PPV molecules is stronger, and this, probably, results in considerable decrease of photovoltage in the region of the excitation of MDMO-PPV.