Interpretation of capacitance measurements on multilayer solar cells
Capacitance measurements are commonly used to estimate defect densities in a solar cell. Ravishankar et al. show that for a solar cell comprising of multiple layers, the traditional analysis of capacitance data is erroneous because the capacitance response of the absorber layer is hidden by overlapping responses from the other layers.
Capacitance measurements are widely used to spatially and energetically resolve doping and defect densities in solar cells. However, the analysis used to calculate these charge densities assumes that the capacitance response originates solely from the absorber layer in question. In this work, using a combination of drift-diffusion simulations and analytical modelling, Ravishankar et al. show that such an assumption is erroneous in the case of perovskite solar cells due to the influence of the thin and resistive transport layers, which hide the capacitance response of the perovskite layer. They identify that this effect dominates the response in several capacitance measurements reported in literature, leading to the calculated doping/defect densities and related parameters largely being artefacts of measurement. Analytical resolution limits are derived for these techniques to distinguish a real defect response from a measurement artefact.
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