All-inorganic cesium lead halide perovskites have been emerging as the promising semiconductor materials for next-generation optoelectronics. However, the fundamental question of how the environmental atmosphere affects their photophysical properties, which is ubiquitous and closely implicated in the practical device applications, remains unclear. I will present the dynamic switching between radiative exciton recombination and non-radiative carrier trapping on the surface of CsPbBr₃ perovskite crystals by controlling the atmospheric conditions. Specifically, it is observed that the photoluminescence (PL) intensity from the CsPbBr₃ crystals grown by both the Bridgman technique and low-temperature solution method can be reversibly modulated by nearly two orders of magnitude through exchanging the surrounding between ambient air and vacuum. Based on the comprehensive steady-state and transient spectroscopic characterization, near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) as well as density functional theory (DFT) calculations, we unraveled that the physisorption of oxygen molecules in air effectively repairs the carrier-trapping states and results in the PL-modulation phenomenon. Our results not only shed light on the impacts of environmental atmosphere on the luminescence and trap states of CsPbBr₃ crystals, but also provide guidance for improving the device performance based on all-inorganic perovskites.

Dr Handong Sun is an associate professor in the School of Physical & Mathematical Sciences, Nanyang Technological University (NTU), Singapore. He received his Ph.D. degrees in Physics from Hong Kong University of Science & Technology in 1999. Before joining NTU, he did postdoctoral research works at RIKEN, Japan and Institute of Photonics, The University of Strathclyde, UK. Dr. Sun is an elected Fellow of American Physical Society. His research theme exists at the interface between optical physics and material science, i.e. light-matter interaction. His current research works focus on Optical Spectroscopic Characterization, Optoelectronic Materials and Devices, Plasmonics Optics, and Applications of Photonics.