Ultrafast charge photogeneration in conjugated polymers

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