Hysteresis and Its Correlation to Ionic Defects in Perovskite Solar Cells

Abstract
Ion migration has been reported to be one of the main reasons for hysteresis in the current–voltage (J–V) characteristics of perovskite solar cells. We investigate the interplay between ionic conduction and hysteresis types by studying Cs0.05(FA0.83MA0.17)0.95Pb(I0.9Br0.1)3 triple-cation perovskite solar cells through a combination of impedance spectroscopy (IS) and sweep-rate-dependent J–V curves. By comparing polycrystalline devices to single-crystal MAPbI3 devices, we separate two defects, β and γ, both originating from long-range ionic conduction in the bulk. Defect β is associated with a dielectric relaxation, while the migration of γ is influenced by the perovskite/hole transport layer interface. These conduction types are the causes of different types of hysteresis in J–V curves. The accumulation of ionic defects at the transport layer is the dominant cause for observing tunnel-diode-like characteristics in the J–V curves. By comparing devices with interface modifications at the electron and hole transport layers, we discuss the species and polarity of involved defects.

Acknowledgements
Y.V. and C.D. thank the DFG for generous support within the framework of SPP 2196 project (PERFECT PVs).

Publisher
American Chemical Society (ACS)

Journal
The Journal of Physical Chemistry Letters

DOI
10.1021/acs.jpclett.3c03146

Additional Links
https://pubs.acs.org/doi/10.1021/acs.jpclett.3c03146