Every software package contains a full set of examples suitable for that version and are installed with the software. If you see examples here that are not in your installation you should consider updating to a later version of the software. These examples can be used by beginners and advanced users for product evaluation, teaching purposes, and self-training.

Required Modules

Victory Device

• 2D Simulator
• 2D Organic

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 energy level cited for the equivalent “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 analogous parameters are also available 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 conjunction with the Gaussian energy distribution of the density of states. In an analogous way to mobility models in crystalline materials, the Pasveer model makes the mobility dependent on both the fraction of filled states (like the conmob model in silicon) and the electric field (like 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 analogous maximum field used in the field dependent mobility model is specified using the FCutoff.N parameter. Once again there are analogous 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.

Reference:
[1] W. F. Pasveer et al., “Unified Description of Charge-Carrier Mobilities in Disordered Semiconducting Polymers “, Physical Review Letters, 94, 206601 (2005)

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