Electrical Simulations of Semiconducting Devices
The ability of extracting physically meaningful parameters from a set of measurements of "macroscopic" quantities is fundamental in modern science.
With the drift-diffusion model that features different charge mobility laws, Setfos allows us to study the influence of the mobility law and the energy diagram of a semiconducting thin film structure on the current-voltage curve.
Charge Mobilities: Constant vs. Field-dependent
- Figure 1: I-V fitting curves calculated with Setfos. The blue curve assumes a constant charge mobility, while the red one refers to the drift-diffusion model with field-dependent charge mobilities.
The example shown in Fig. 1 demonstrates the difference between constant and field-dependent mobility laws for a single-layer polymer OLED. In this example, Setfos is able to simulate field-dependent as opposed to constant charge mobility to better suit the measured data. Figure 1 shows the fit of a I-V measurement approximated assuming a "constant mobility" (blue curve) and the improvement in the trend accuracy when implementing a "field-dependent charge mobility" (red curve).
- Figure 2: Thickness scaling of current-voltage curves with fixed material parameters.
The same energy parameters calculated to fit the data presented in Figure 1 have been successfully applied to approximate I-V curves of devices with different semiconducting layer thicknesses, see Figure 2. The accuracy of the first fitting procedure is revealed by the quality of the calculated curves depicted here.
Extended Gaussian Disorder Mobility (EGDM)
- Figure 3: IV curve of a single layer, bipolar device made of the PPV-based "SuperYellow" material (OC1C10-PPV) sandwiched between a Gold anode and a Calcium cathode.
Setfos is the first organic semiconducting numerical simulator implementing the Extended Gaussian Disorder Mobiliy model (EGDM). The model is based on the energetic disorder of the energy levels: this affects not only the charge mobility but also the injection characteristics of the device.
- Electron mobility and electric field profiles for the different applied voltages as in Fig. 3.
- Comparison of charge density profiles for curves calculated with constant and EGDM mobility.