Targeted suppression of hysteresis effect in perovskite solar cells through the inhibition of cation migration

The hysteresis effect is a vital issue in perovskite solar cells that warrants close scrutiny, of which ion migration and the resultant interfacial ion accumulation are widely considered to be the most important origination. However, owing to the lack of specific characterization tools to disentangle the complicated interaction between ions and charge carriers, it is yet unidentified which ionic species govern the hysteresis effect, bringing difficulties in further device optimization. Herein, adopting a home-built circuit-switched transient photoelectric technique, whereby ion migration dynamics can be studied without interference from photogenerated charge carriers, the role of different ions in the photoelectric conversion process is elucidated. As suggested by the experimental results, the hysteresis effect dominantly arises from the migration of organic cations instead of the halide anions and can be well interpreted in terms of the strongly coupled cation–electron pairs. On the basis of these findings, we showcase the effectiveness of suppressing the hysteresis factor by the inhibition of the methylamine cations' migration. The present work can provide targeted and sufficient guidance for the preparation of high-stability and high-efficiency perovskite solar cells.