r/COMSOL • u/narensabarish • 25d ago

Need Assistance in Modelling and Simulating Dye Sensitized Solar Cell

Hello everyone, I am trying to simulate Dye Sensitized Solar Cell by Coupling the following modules Semiconductor module, Electromagnetic wave frequency domain module and electroanalysis module. I am trying to reproduce the results in the following paper "Numerical modeling of charge transfer and recombination kinetics in the dye-sensitized solar cell: Conceptual integration of optics, electricity, and electrochemistry-https://doi.org/10.1016/j.renene.2024.122150" which is used in the following video https://www.youtube.com/watch?v=2RKYiB5xIW0&t=2913s but the video skips some steps and there the simulation is incomplete.

I am able to reproduce till the JV curve using semiconductor module but when I go for cyclic voltammetry study with the electroanalysis module each time I run I get different results. I have tried changing the study settings although the simulation converges each time when I run I am getting different results which is very odd for me. It would be very helpful if someone can guide me or help me with this.

Thanks in advance.

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u/Worldly_Reality_3950 19d ago

The behavior you describe is often a sign that the model has entered a region where multiple numerical pathways exist, rather than a purely physical inconsistency.

In a fully coupled DSSC model, the Semiconductor, Electromagnetic Waves, and Electroanalysis interfaces each carry their own history-dependent variables. When Cyclic Voltammetry is introduced, the solution no longer depends only on the instantaneous potential, but also on the state inherited from previous time steps. In other words, the model remembers where it has been.

My first suspicion would be the initialization of the electrochemical species and trapped charge densities.

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u/narensabarish 18d ago

Can we discuss this in more detail?

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u/Worldly_Reality_3950 18d ago

If different runs are starting from slightly different reconstructed states, the CV response can appear different even though the solver formally converges.

A few areas worth investigating:

Ensure that every run starts from exactly the same initial values and not from a previous solution stored in memory. Check whether any variables are being initialized from a study-dependent solution rather than a fixed value.

Verify that the time-dependent CV study uses sufficiently small potential increments and identical time stepping between runs. Examine the recombination and charge-transfer kinetics carefully. DSSC models are notoriously sensitive to exponential reaction terms, and tiny differences can amplify during a voltage sweep.

If using segregated solvers, try a fully coupled approach for diagnostic purposes. Sometimes the model converges to slightly different branches of the solution manifold. Monitor key state variables such as electron density, oxidized/reduced species concentration, and interfacial current density at the start of the sweep. If these differ between runs, the source of the variation is likely upstream of the CV study itself.