Perovskite/Organic Device Tutorial – Simulating SCLC
1. Introduction
Space-charge limited current (SCLC) occurs when the current through a device is limited by the transport of injected carriers rather than by generation. In this regime, the current density follows the Mott–Gurney law:
\( J = \frac{9}{8} \, \varepsilon \mu \, \frac{V^2}{L^3} \)
where ε is the dielectric constant, μ the carrier mobility, V the applied voltage, and L the thickness. Experimentally, SCLC is one of the most widely used methods to extract carrier mobility and trap densities in organic and perovskite semiconductors.
2. Setting up the simulation
Launch OghmaNano and open the New simulation window (??). Choose the SCLC diode template (or, if not present, select a generic perovskite diode and configure the contacts for hole-only or electron-only transport). This sets up a simple test device where injected carriers dominate the current.
3. Running the simulation
Switch the Simulation type to JV curve.
Set the voltage range from 0 to a few volts (e.g., 0–5 V).
Press Run simulation (blue play button) or F9.
Once complete, open the Output tab and plot jv.csv
(??).
4. Analysing SCLC
In the log–log plot of J vs V, the SCLC regime appears as a slope ~2. From the curve, you can apply the Mott–Gurney law to estimate the carrier mobility. If traps are included, the slope deviates from 2, allowing estimation of trap density and energy distribution.
📝 Task 1 — Voltage sweep
Run the JV simulation over 0–5 V. Re-plot in log–log scale and identify the region where the slope is ~2.
Expected observation
The SCLC regime appears as a straight line with slope ≈ 2 in log–log space. Below this, current is limited by injection; above this, series resistance may dominate.
🧪 Task 2 — Change mobility
In the Electrical parameters, change the carrier mobility by ×10 up and down. Re-run the simulation and overlay the curves.
Expected observation
The J–V curve shifts vertically in proportion to the mobility. Higher mobility → higher current at the same voltage, while the quadratic slope remains unchanged.
⚡ Task 3 — Add traps
Enable trap states (e.g. Gaussian or exponential tail) in the Electrical parameters. Compare the JV curve with and without traps.
Expected observation
With traps, the slope in log–log space deviates from 2 (often between 2 and 4). The onset voltage shifts higher, indicating reduced carrier collection efficiency.
✅ What you’ve learned
- How to set up and run an SCLC simulation in OghmaNano.
- How to identify the quadratic J–V regime and use it to extract mobility.
- How traps modify the slope and onset of the SCLC curve.
- How simulation helps interpret experimental SCLC data.