title: Unification of trap-limited electron transport in semiconducting polymers.
abstract: Electron transport in semiconducting polymers is usually inferior to hole transport, which is ascribed to charge trapping on isolated defect sites situated within the energy bandgap. However, a general understanding of the origin of these omnipresent charge traps, as well as their energetic position, distribution and concentration, is lacking. Here we investigate electron transport in a wide range of semiconducting polymers by current-voltage measurements of single-carrier devices. We observe for this materials class that electron transport is limited by traps that exhibit a gaussian energy distribution in the bandgap. Remarkably, the electron-trap distribution is identical for all polymers considered: the number of traps amounts to 3 × 10(23) traps per m(3) centred at an energy of ~3.6 eV below the vacuum level, with a typical distribution width of ~0.1 eV. This indicates that the electron traps have a common origin that, we suggest, is most likely related to hydrated oxygen complexes. A consequence of this finding is that the trap-limited electron current can be predicted for any polymer.
authors: Molecular Electronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands.
authors: H T
authors: HT
authors: Nicolai
authors: M
authors: M
authors: Kuik
authors: G A H
authors: GA
authors: Wetzelaer
authors: B
authors: B
authors: de Boer
authors: C
authors: C
authors: Campbell
authors: C
authors: C
authors: Risko
authors: J L
authors: JL
authors: Brédas
authors: P W M
authors: PW
authors: Blom