Time-delayed charge-injection effects on photocurrent shape in a double layer

Picos-Vega, A.; Zelaya-Ángel, O.; Ramı́rez-Bon, R.

doi:10.1103/physrevb.61.12045

Cited by 2 publications

(1 citation statement)

References 9 publications

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“…Instead, we investigate here the idea that the flat plateau, universality, and the approximately t −2 current decay in the tails, as well as the cusps that occasionally occur, may all be caused by a delay of the charge carriers which arises, not just from traps right at the interface but from a trap-rich surface layer that penetrates from the interface into the bulk of the film. The idea that cusps may be caused by the presence of a surface layer in MDPs that has different trapping characteristics than the bulk has been suggested before. − Tyutnev, et al , have suggested that there is a thin, approximately one micrometer thick, trap-rich surface layer that causes the charge to be delayed before it crosses into the bulk. Indeed, according to this proposal it is the interplay between the depth of the charge generation region and the thickness of the surface region that determines the particular transient shape seen in any given time-of-flight measurement.…”

Section: Introductionmentioning

confidence: 99%

Two-Layer Mutiple Trapping Model for Universal Current Transients in Molecularly Doped Polymers

Dunlap

Schein²,

Tyutnev

et al. 2010

J. Phys. Chem. C

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The mechanism of charge transport in molecularly doped polymers has been the subject of much discussion over the years. In this paper, data obtained from a new experimental variant of the time-of-flight (TOF) technique, called TOF1a, are compared to the predictions of a two-layer multiple trapping model (MTM) with an exponential distribution of traps. In the recently introduced TOF1a experimental variant, the charge generation depth is varied continuously, from surface generation to bulk generation, by varying the energy of the electron-beam excitation source. This produces systematic changes in the shape of the current transient that can be compared to predictions of the two-layer MTM. In the model, one additional assumption is added to the homogeneous MTM, namely: that there exists a surface region, on the order of a micrometer thick, in which the trap distribution is identical to the bulk, but has a higher trap concentration. We find that the characteristic experimental features of an initial spike, a flat plateau, and an anomalously broad tail, as well as the sometimes observed cusp or decreasing current occurring near the transit time, can all be described by such a two-layer model; that is, they can arise as a result of carriers delayed by a trap-rich surface layer. We find that we can semiquantitatively fit current transient data over the whole time range of the experiment, but only by using theoretical parameters that lie in a narrow range, the extent of which we quantify here.

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