Study of Charge Transport Kinetics and Diffusion at Hybrid Perovskite- Liquid Electrolyte Interface by Electrochemical Impedance Spectroscopy

A lot of research has been done on the efficiency improvement of Perovskite Solar Cells by optimization of the film morphology using various techniques including electrochemical impedance spectroscopy (EIS) in a solid-state active device geometry.¹ Recently, the optimization of the film morphology at liquid electrolyte interface by EIS is trending as a more simplified and accurate approach. ^2,3
Here, we have studied the charge transfer at the methylammonium lead tri-iodide (MAPbI₃) perovskite-liquid electrolyte interface under the effect of applied bias. By applying the different dc bias from +1V to -1V, it was found that the ion diffusion at low-frequency regime changes significantly with bias. Also, the films show the same trend of change in impedance under positive and negative bias, which reveals the ambipolar nature of the hybrid perovskites. The ions migrate more under light and get accumulated at the interface in the dark as depicted by the Nyquist plot. We have simulated a model to explain the charge kinetics across the interface with different applied bias under dark and light.
References
1. Bag, M. et al. J. Am. Chem. Soc. 2015, 137 (40), 13130–13137.
2. Li, Z. et al. Chem. Commun. 2017, 53 (16), 2467–2470.
3. Srivastava, P. et al. ACS Appl. Energy Mater. 2018, 1, 4420–4425.