Ultrafast photogeneration of charged polarons in conjugated polymers - art. no. 081201

Ultrafast photoinduced absorption by infrared-active vibrational modes (IRA V) is used to detect charged photoexcitations (polarons) in conjugated lumi nescent polymers. The experiments, carried out in zero applied electric fie ld, show that polarons are generated instantaneously (within similar to 100 fs) with appreciable quantum efficiencies, phi (ch) similar to 10%. The ul trafast photoinduced IRAV absorption, the weak pump-wavelength, dependence Of phi (ch) and linear dependence of charge density on pump intensity indic ate that both charged polarons and neutral excitons are independently gener ated even at the earliest times. Several mechanisms for charge generation p roposed in the literature are eliminated by these results.