Time resolved ESR measurements of photoinduced polarons in PPV

To study the early stage of photoexcitation in poly(paraphenylene vinylene) (PPV), we have performed a time-resolved measurements of light-induced ESR (LESR). Transient photo-induced spins with two decay components are clearly observed. Its time constant of the order of a few micro-second for the faster component is comparable with previous transient-photocurrent data of a PPV derivative. The observed spectral shape accords with the previous results of cw-LESR, indicating that the observed signal is due to photo-induced polarons.