Regensburg 2002 – wissenschaftliches Programm

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SYOH: Organische Halbleiter

SYOH 7: Poster

SYOH 7.28: Poster

Montag, 11. März 2002, 18:00–21:00, C

Hopping within a Gaussian Shaped DOS: A Statistical Approach — •Roland Schmechel and Heinz von Seggern — TU-Darmstadt, FB: Materialwissenschaft, FG: Elektronische Materialeigenschaften, Petersenstrasse 23, 64287 Darmstadt

The hopping transport in a system of purely localized states within a Gaussian shaped DOS is theoretically investigated on basis of the Miller-Abraham model by statistical laws. It was found that an electron in the tail of the DOS is most probably released at an energy E_esc near the center of the Gaussian DOS and subsequently relaxes to a target state at energy E_t slightly below E_esc. Both energies E_esc and E_t are found to be independent of the initial energy level E₀ the carrier occupies before the hop. E_t has a similar meaning as the transport energy in the exponential tails of an amorphous inorganic semiconductor. It will be shown that the main contribution to the total transport current is carried by states close to E_t. Based on these ideas, a simplified model is presented, in which the complex hopping transport is described by a multipletrapping and release model. Within this model states below E_t act as traps. It will be demonstrated that the characteristic non-Arrhenius law for the temperature dependence of the mobility of charge carriers in organic semiconductors can be derived from this model. The results will be discussed with respect to the interpetation of TSC measurments and the effect of doping on the transport process.