Ultrafast charge photogeneration in conjugated polymers

The mechanism for ultrafast charge generation in po ly(paraphenylene-vinylene)-PPV and its soluble derivatives has been investigated by pump-probe spectroscopy. The quantum yield for charge generation (phi (ch)) as a function of pump photon energy has been measured by exciting the samples with ultrashort pulses (2.2 to 6.2 eV, similar to 100 fs pulsewidth) and probing the photoinduced absorption of infrared-active vibrational modes (IRAV). The ultrafast nature of charge generation, the significant quantum yield observed (phi (ch) similar to 0.1) and its weak photon energy dependence suggest that polarons are primary photoexcitations of conjugated polymers.