Quantum efficiency and initial transport of photogenerated charge carriers in π-conjugated polymers

We have measured the quantum efficiency and initial transport of photogenerated charge carriers in two chemically very different, pi-conjugated polymers, namely regiorandom poly(3-hexylthiophene) and a copolymer poly(9,9-dioctyl-fluorene-co-bis-N,N'-(4-butyl-phenyl)-bis-N,N'-phenyl-1,4-phenylenediamine) (PFB), using integral mode time-of-flight (TOF). We show how to separate the quantum efficiency of charge generation from the fast initial (pretrapping) drift distance. The quantum efficiency of charge generation is strongly field and wavelength dependent, but very weakly temperature dependent, in good agreement with the model for hot exciton dissociation proposed by Arkhipov [Phys. Rev. B 61 (2000) 8207]. We also measured the initial (pretrapping) drift distance l(f) = 20-100 nm, strongly field dependent, but independent on wavelength and temperature. (C) 2003 Elsevier Science B.V. All rights reserved.