Direct Observation Of Photoinduced Ion Migration In Lead Halide Perovskites

Unique optoelectronic, electronic, and sensing properties of hybrid organic-inorganic perovskites (HOIPs) are underpinned by the complex interactions between electronic and ionic states. Here, the photoinduced field ion migration in HOIPs is directly observed. Using newly developed local probe time-resolved techniques, more significant CH3NH3+ migration than I-/Br- migration in HOIPs is unveiled. It is found that light illumination only induces CH3NH3+ migration but not I-/Br- migration. By directly observing temporal changes in bias-induced and photoinduced ion migration in device conditions, it is revealed that light illumination suppresses the bias-induced ion redistribution in the lateral device. These findings, being a necessary compensation of previous understandings of ion migration in HOIPs based on simulations and static and/or indirect measurements, offer advanced insights into the distinct light effects on the migration of organic cation and halides in HOIPs, which are expected to be helpful for improving the performance and the long-term stability of HOIPs optoelectronics.