Single particle spectroscopy on composite MEH-PPV/PCBM nanoparticles

The preparation and characterization of composite MEH-PPV/PCBM nanoparticles with doping levels up to 75 wt% PCBM is reported. These nanoparticles represent structures in between single molecules and bulk that allow for a detailed investigation of the role of nanostructure on the properties of the corresponding functional materials. Combining this material system with single particle spectroscopy studies reveals molecular scale information on the extent to which variations in polymer chain folding and interactions between polymer chains and fullerenes affect material morphology and photophysical properties. Key observations are that the single particle ensemble spectra shift with respect to each other depending on PCBM doping levels, and that the vibronic structure of the single particle ensemble spectra changes with PCBM doping levels. These observations are indicative of a reduction in conducting polymer conjugation length and interchain interactions due to steric effects caused by the presence of PCBM that result in reduced exciton transport.