Temperature-dependent exciton dynamics in poly(p-phenylene vinylene) measured by femtosecond transient spectroscopy

Exciton delocalization in the conjugated polymer poly(p-phenylene vinylene) (PPV) is investigated using temperature-dependent spectroscopy. As the temperature is lowered, the steady-state absorption and fluorescence spectra indicate increased electronic conjugation and exciton delocalization. Femtosecond transient absorption measurements at 20 and 290 K over the wavelength range 520–650 nm provide evidence that such delocalization occurs within the first 10 ps after photoexcitation. Comparison of the 20 and 290 K data, along with anisotropy studies, suggests that vibrational cooling plays a significant role in the spectral dynamics observed in PPV on this timescale.