Dependence of poly(p-phenylene vinylene) morphology and time-resolved photophysics on precursor solvent

The effects of precursor solvent on the optical properties and morphology of poly(p-phenylene vinylene) (PPV) films are investigated using X-ray diffraction, steady state absorption and fluorescence, and picosecond time-resolved spectroscopy. Precursor films spin cast from water yield PPV films with higher average crystallite size and conjugation than films cast from methanol. These changes affect not only the steady state absorption but also the femtosecond stimulated-emission spectra, which are narrower and red-shifted in water cast films. This indicates that PPV’s short time spectral behavior is sensitive to the details of sample preparation. Fluorescence decay measurements from 100 ps to nanoseconds at temperatures ranging from 16 to 290 K are the same for both samples, however, indicating that the longer time exciton dynamics remain unaffected.