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-butyric acid methyl ester (PCBM), with poly(para-phenylenevinylene) (PPV) synthesized using a novel nonionic precursor route were produced. These photoactive blends have been investigated by excited-state spectroscopy and by photocurrent measurements. UV-vis and IR absorption measurements, as well as luminescence spectroscopy, were used to monitor the conversion process of the precursor polymer to the PPV in blends with PCBM. The presence of PCBM did not influence the successful conversion process. The occurrence of photoinduced charge transfer, well-known for blends of substituted PPV with fullerenes, was evidenced in composites of PPV/PCBM by the strong quenching of the PPV luminescence. LESR (light induced electron spin resonance) and PIA (photoinduced absorption) studies confirmed the occurrence of photoinduced electron transfer from the PPV to PCBM within the bulk of solid state composite films. Photovoltaic devices made from PPV/PCBM blends showed power efficiencies of up to 0.25% under intense white light illumination. The spectral - photocurrent excitation profile was observed to follow closely the absorption spectrum of the PPV.