Interpretation of time constants from frequency domain measurements of perovskite solar cells

Ravishankar et al. developed a model to describe the frequency domain response of perovskite solar cells with an emphasis on the role of transport layers. Application to experimental data identifies that measured time constants are limited by charge carrier extraction rather than by recombination.

Frequency domain small-perturbation measurements are useful tools to understand physical processes occurring at different timescales in the solar cell. In the case of perovskite solar cells, the analysis of the measured frequency domain spectra is typically carried out by considering transport and recombination processes in the perovskite layer. However, state-of-the-art perovskite solar cells (PSC) are mostly limited by poor charge extraction from the perovskite to the electrode, via the low-mobility transport layers. To solve this problem, Ravishankar et al. developed a model that accounts for the coupled effects of charge extraction and recombination in the PSC. This model predicts the existence of two time constants in the frequency domain data and their evolution versus the open-circuit voltage for different measurement techniques: impedance spectroscopy (IS), intensity-modulated photocurrent spectroscopy (IMPS) and intensity-modulated photovoltage spectroscopy (IMVS). Analysis of experimental data using the model allows effectively decoupling regions in the response that are dominated by either recombination or charge extraction and calculation of relevant parameters such as the charge extraction velocities of the transport layers.

Further information can be found here:
https://journals.aps.org/prxenergy/abstract/10.1103/PRXEnergy.2.033006