Photoactive blends of poly(para-phenylenevinylene) (PPV) with methanofullerenes from a novel precursor: Photophysics and device performance

Homogeneous blends of a processable methanofullerene, [6,6] phenyl C-61-but yric acid methyl ester (PCBM), with poly(para-phenylenevinylene) (PPV) synt hesized using a novel nonionic precursor route were produced. These photoac tive blends have been investigated by excited-state spectroscopy and by pho tocurrent measurements. UV-vis and IR absorption measurements, as well as l uminescence spectroscopy, were used to monitor the conversion process of th e precursor polymer to the PPV in blends with PCBM. The presence of PCBM di d not influence the successful conversion process. The occurrence of photoi nduced charge transfer, well-known for blends of substituted PPV with fulle renes, was evidenced in composites of PPV/PCBM by the strong quenching of t he PPV luminescence. LESR (light induced electron spin resonance) and PIA ( photoinduced absorption) studies confirmed the occurrence of photoinduced e lectron transfer from the PPV to PCBM within the bulk of solid state compos ite films. Photovoltaic devices made from PPV/PCBM blends showed power effi ciencies of up to 0.25% under intense white light illumination. The spectra l - photocurrent excitation profile was observed to follow closely the abso rption spectrum of the PPV.