Pasveer Hopping Mobility Model and Gaussian DOS : Pasveer Hopping Mobility Model and Gaussian DOS

Requires: Blaze/Organic Display
Minimum Versions: Atlas 5.24.1.R

This example compares I-V curves generated using the Pasveer hopping mobility model [1] with using a constant mobility model when using a Gaussian energy distribution of band states. It also shows the effects of electron concentration throughout the device for different structure bias. An explanation of the Pasveer mobility model together with the gaussian energy density of states distribution and diffusion models is briefly described below.

Gaussian Density of States Energy Band Structure

It has been found that the band structure of organic materials is better represented by a gaussian energy distribution for the density of states rather than using the normal parabolic energy distribution of states used for crystalline semiconductor materials. The average eneregy level cited for the equivilent "valence" and "conduction" bands in organic materials, is therefore in the middle of the gaussian energy distribution, rather than at the band edges of the distribution as in the case for ordered crystalline materials.

A gaussian energy band distribution is specified on the material statement, where for the conduction band, the total density of states is specified by setting the NtC.gauss parameter and the width of the gaussian distribution is set by the SigC.gauss parameter. Two analagous parameters are also avalable for the valence band.

Pasveer Hopping Mobility Model [1]

Also demonstrated in the example is the Pasveer hopping mobility model [1], which was developed to be used in conjuction with the Gaussian energy distribution of the density of states. In an analagous way to mobility models in crystalline materials, the Pasveer model makes the mobility dependent on both the fraction of filled states (similar to the conmob model in silicon) and the electric field (similer to fldmob).

To activate the Pasveer hopping mobility model for electrons, specify Pasveer.N on the mobility statement. The parameter that determines the maximum carrier density used in the carrier dependent mobility model is specified using the CCutoff.N parameter, and the analagous maximum field used in the field dependent mobility model is specified using the FCutoff.N parameter. Once again there are analagous parameters for the valence band.

Diffusion Model

The diffusion model resulting from a gaussian distribution of states necessitates a corrective term to the Einstein diffusion relationship which is also included in the models.

[1] The Pasveer reference publication is as follows: W.F.Pasveer et al., Physics Review Letters, 94, 206601 (2005)

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