Title: Ion-electron interaction and Ionic Role in Halide Perovskites

Speaker: Xiaoming Wen, RMIT University

Time: October 26, 2023 (Thursday) at 10:00 am

Venue: Lecture Room C3c-204, GZIC

Abstract:

Halide perovskites have emerged as revolutionary materials for high performance photovoltaics and optoelectronics due to their superior optoelectronic properties. The important feature of halide perovskites and alloy perovskites is their mixed ionic-electronic conduction. However, ionic role is mostly understood as mobile ion as the source of a series detrimental effects, such as I-V hysteresis, phase segregation and instability. On the other hand, the ionic beneficial effects are ignored, the influence of ionic on the carrier lifetime is not considered and a fundamental question: what makes halide perovskites supervisor optoelectronic properties? still remain elusive. The understanding on the anomalous ultraslow variations under illumination, such as defect curing and defect tolerance, so far stays in phenomenological explanation, but lack of deep physical mechanism.

In this presentation, we state the multiple ionic roles in halide perovskites, which results in the beneficial and detrimental effects. We consider ionic influence on electronic dynamics by introducing new concepts of ionic energy reservoir, ion-electron coupling and ion-phonon scattering. Our hypothesis consistently interprets that the electron detrapping directly leads to significantly enhanced fluorescence efficiency and prolonged carrier recombination lifetime, which is responsible for the excellent device performance of halide perovskites. By adding the ion-electron coupling into the rate equations of photogenerated carrier, we establish the physical correlation between electronic dynamics in the timescale of nanosecond-microsecond and ionic dynamics in the timescales of second to hour. This finding adds the missing puzzle into the holistic physics picture and provides a deep understanding of halide perovskites. Our results suggest the possibility of maximizing the potential of halide perovskite devices through enhancing ion-electron coupling.