Welcome !

Welcome to our new free Organic Transistor modelling software, available from your preferred web browser, from everywhere, at any time ! You will be able to estimate many of your device electric characteristics using this software: C(V G ), I D (V D ), I D (V G ), threshold voltage, apparent mobility, etc You will be able to estimate the influence of contact parasitics, such as series resistances or non-linear injection barriers, and more.

This 0.3.5 upgrade brings many news features, improvements and bug corrections (see Whats new in this release).

This is a scientific simulation software, devoted to scientific application. However very little knowledge of the OFET is required. A set of default parameters is provided to help you, and you may adapt these to your own device design and technology. You can save, upload and download your parameter set so as to keep it from day to day if needed. Many output graphs are provided, in both jpeg and numeric formats. You will be able to use them directly or with your preferred data analysis software.

This modelling software is a beta release. Despite our efforts, there might be some circumstances where it fails to simulate your particular parameter set. We would very much appreciate your feed-back. Please feel free to tell us what you would like to see improved, added, corrected, etc Your comments will be taken very seriously.

We hope this software will help you gain knowledge of your own device.

Enjoy !

Coming soon...

Actually under beta test, many new features will become available to you in a near feature:

gradual channel approximation, or NOT ! The electric field variation along the channel plays a very important role in short channel devices : poor saturation, or even no saturation. This also deeply modifies various profiles along the channel, like sheet conductivity, accumulated charges, mobility, etc...

exponential DOS will be available with associated transport model to describe carrier trapping in the band gap allowing to reproduce subthreshold slope variation.

further reduced computing time : a complete characteristic, whatever the considered model with any combined effects, is obtained in about a minute

comparison with analytic expressions (when applicable): numerical results can be compared with analytical expressions of the drain current (when they are available) i.e. with an ideal transistor or when only series resistances are considered.

leakage resistances: various leakage resistances can be added to account for experimental impairments

Whats new in this release:

v 0.3:

field activation of the mobility is now available (Poole-Frenkel effect). It plays a significant role in the output characteristic and can induce non linear I(V) curves, comparable to injection barriers. You can compare these effects, or simulate any combination.

reduced computing time

minor bug corrections in the web interface

v 0.2.7:

the temperature can be set between a few K and a few hundred K. This will impact internal data: Fermi-Dirac occupation statistics, Gaussian DOS, mobility, injection current density, diffusion current density. This will not change other material parameters, such as the band gap, relative permittivity, etc due to the lack of available temperature models for these parameters in organic materials. All the parameters defined in the user interface are kept constant.

various mobility models have been implemented to account for experimental observations in organic transistors. The user is invited to read the cited scientific publications for application of these models to its own device.

an interface layer can be inserted between the gate insulator and the organic channel layer. This layer is provided to account for traps at the insulator interface. It behaves exactly as the channel material but with different and adjustable material parameters.

source and drain series resistances depending on gate voltage for top contact structures can now be simulated. In bottom contact structures the contact model remains injection based due to the very thin injecting surface.

more plots are available

interface improvements, speed improvement, some bugs fixed

Model description:

Most of the model physics can be find in [1,2,3]. The simulation is in two steps:

First, a numerical resolution of your gate metal/insulator/organic semiconductor stack is performed, in order to obtain the free charge available for conduction in the transistor channel, at a given gate bias. This is done for a set of 1000 gate bias points, and takes about a minute. Many outputs are available from this simulation, such as band diagram, carrier concentrations, quasi-static capacitance versus voltage, etc The 1D Poisson equation at equilibrium is solved using amorphous organic material statistics, ie Gaussian density of states. Unless donor or acceptor concentrations are given in the parameter set, an undoped (intrinsic) organic semiconductors is considered in accumulation mode. Also, usually a single charge carrier is considered to be mobile in the semiconductor channel (either n or p ). However, both n and p concentrations are calculated during this step, the other carrier being considered frozen in a given position with its own charge (like if it was spatially and energetically trapped in its own energy band at a given channel position).

or ). However, both and concentrations are calculated during this step, the other carrier being considered frozen in a given position with its own charge (like if it was spatially and energetically trapped in its own energy band at a given channel position). Then, based on this available free moving charge, the drain current along the channel is calculated for the set of drain and gate voltages you require (about half a second computing time by bias point, ie about 2 minutes for a standard I D (V D ) characteristic). To do so, the channel is discretized into a number of slices in which all relevant quantities are calculated (potential, electric field, mobile charge, mobility, drift and diffusion currents, etc ). Finally, the current versus voltage characteristics are computed.

(V ) characteristic). To do so, the channel is discretized into a number of slices in which all relevant quantities are calculated (potential, electric field, mobile charge, mobility, drift and diffusion currents, etc ). Finally, the current versus voltage characteristics are computed. Contact parasitics are considered in two different ways. Ohmic (linear) drain and source resistances R S and R D can be set to a constant value. Additionally, non-linear injection at the source contact has been implemented, following the model described in [3]. Details of the implementation can be found in [2].

and R can be set to a constant value. Additionally, non-linear injection at the source contact has been implemented, following the model described in [3]. Details of the implementation can be found in [2]. Various mobility models are available, from a simple constant mobility model, to an advanced model taking into account specific properties of disordered materials, where the mobility may depend on the carrier concentration, the DOS shape, or the temperature [6].

Outputs:

All output plots you have selected will be displayed in your browser as a JPEG. You will be able to collect all JPEGs and all the corresponding numerical data in a zip archive available for download in the Simulation Results window.

Model validation:

A simple validation of the software can be made comparing the numerical outputs with analytic expressions available for simple structures well above threshold (like Q=C·U or I D =(W/L)µC i (U GS -U T )2 in saturated regime). Embedded mesh parameters (both for charge calculation and OFET channel slicing) have been adjusted so as to compromise between speed and precision. Using the present mesh settings, compared with analytic expressions, we found negligible error for Q, and about a 1% for I D .

Computing time:

The overall simulation time should not exceed 2 minutes for standard outputs (about 100 bias points). The higher number of bias points you require, the longer the simulation time. While our server is running, your web browser will react as if it was waiting for a page to load: please be patient ! The figures will draw automatically in the Simulation Results window when your simulation is completed. Your device is absolutely free in the meanwhile. If you leave our web page however, you will not recover your results !

Where the software runs:

No software will be loaded on your machine. You can use any terminal running a web browser: your favorite smartphone or iPad will work too. Your parameter file will be loaded on our local server (located in Reims University), where the simulation software runs. All your files are deleted from the server when you leave the web page: do not forget to download your parameters and results! A cookie will be created on your machine to guaranty secured access to your data. Please unable your browser to allow it.

Confidentiality:

it is not our intention to collect any kind of data concerning the users of this modelling software. No login or personal identification is required. No identification of any kind (IP address or other) will be used. All your data will be available only to you, and will be deleted from the server the day after you leave our web page. Consequently, all simulation parameters and simulation results will be lost, unless you download the parameter file and the Simulation Results zip file, where all the figures and output data will be included.

References:

[1] L. Giraudet, O. Simonetti, Threshold voltage and turn-on voltage in organic transistors: sensitivity to contact parasitics, Organic Electronics 12, 219 (2011)

[2] O. Simonetti, L. Giraudet, T. Maurel, J.-L. Nicolas, A. Belkhir, Organic transistor model with nonlinear injection: effects of uneven source contact on apparent mobility and threshold voltage, Organic Electronics 11, 1381 (2010)

[3] J. C. Scott, Metal-organic interface and charge injection in organic electronic devices, J. Vac. Sci. Technol. A 21, 521 (2003)

[4] N. Karl Synthetic Metals 133-134 649 (2003)

[5] T. Sakanoue and H. Sirringhaus Nature Materials 9,736740 (2010)

[6] J. Cottaar et al. PRL 107 136601 (2011)