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IMVS Tutorial (Intensity-Modulated Voltage Spectroscopy)

1. Introduction

Intensity-Modulated Voltage Spectroscopy (IMVS) probes the small-signal voltage response of a device to a sinusoidally modulated light source. By sweeping modulation frequency, IMVS reveals characteristic time constants related to recombination and transport, complementing IMPS and standard impedance spectroscopy. In OghmaNano, IMVS runs on top of the full opto-electronic model, so optical generation, recombination and transport are treated consistently across the frequency sweep.

2. Getting started

From the New simulation tab in the file ribbon, open the New simulation window (see Figure 1a). Double-click the IS/IMPS/IMVS/CV examples to see ready-to-run frequency-domain projects (see Figure 1b). For this tutorial we’ll use an IMVS example based on a PM6:Y6 OPV stack, but the steps are the same for other technologies.

New simulation window with IS/IMPS/IMVS/CV category visible.
The New simulation window in OghmaNano showing frequency-domain examples.
List of IMVS example projects (PM6:Y6 variants) after opening the frequency-domain category.
Example list. Pick an IMVS project to start.

3. Run the simulation & inspect outputs

Simulation type ribbon with IMVS highlighted.
Select IMVS in the Simulation type ribbon.
Main OghmaNano window showing the 3D device stack and Run simulation button.
The main window. Click Run simulation to execute the IMVS sweep.

Once the project is open you’ll see the device stack in the main view (??). In the Simulation type ribbon choose IMVS (??), then press Run simulation. After completion, IMVS result files (e.g. fx_img.csv, fx_phi.csv, and real_imag.csv) are written to the output directory and can be re-plotted at any time from the Editors → FX domain editor.

4. Frequency mesh & configuration

Frequency mesh tab showing segments across decades with a rainbow preview of frequency points.
Frequency mesh. Define start/stop and point density per segment.
IMVS Configure tab showing excitation, measurement, modulation depth and output options.
Configuration. Set excitation: Light, measure: Voltage, modulation depth, and output verbosity.

IMVS excites the device with a small sinusoidal light modulation and measures the resulting voltage response. Use the Frequency mesh tab to define the sweep (decade segments and resolution) and the Configure tab to choose excitation/measurement channels, modulation depth, number of cycles, and output preferences (see ?? and ??).

5. Reading the plots

Bode amplitude plot: Im(v) versus frequency for the IMVS simulation.
Bode (amplitude): Im(v) vs frequency. Peaks indicate characteristic time scales.
Bode phase plot: φ(v) versus frequency for the IMVS simulation.
Bode (phase): φ(v) vs frequency. Phase trends help separate processes.
Nyquist plot: Re(v)–Im(v) with frequency labels along the arc.
Nyquist: Re(v) vs Im(v) with frequency annotations. The arc’s apex typically pinpoints the dominant time constant.

The Bode amplitude Im(v) and phase φ(v) plots show how the device filters a sinusoidal light perturbation. A maximum in amplitude and rapid phase transitions often indicate a dominant recombination time. The Nyquist projection (??) traces the complex voltage response as frequency changes; the frequency labels along the arc help you associate features with absolute timescales. You can re-plot or export any curve from the Editors → FX domain editor.

💡 Tasks: Try these small changes to see how the spectra respond:

✅ Expected results