Imaging Atomic Structure of Hybrid Perovskite CH3NH3PbI3

Hybrid organic-inorganic perovskites (HOIPs) have attracted great research interest as promising materials for the next generation photovoltaic energy harvesting, electro-optic detection, and all-optical conversion. Their remarkable chargetransport and absorption properties are underpinned by hybrid perovskite atomic structures.

Understanding the atomic structure and structural instability of organic-inorganic hybrid perovskites is the key to appreciate their remarkable photoelectric properties and understand failure mechanism.

However, atomic imaging of OIHPs by electron microscopy is challenging due to the extreme beam sensitivity. So far, the damage-free pristine structure of CH3NH3PbI3(MAPbI3) has never been captured at the atomic scale.

Recently, Dr. WANG Xiao’s group at the Shenzhen Institute of Advanced Technology (SIAT) of the Chinese Academy of Sciences collaborated with Dr. ZHAO Jinjin, Dr. LI Jiangyu and Dr. GAO Peng’s team from Shijiazhuang Tiedao University, Southern University of Science and Technology and Peking University respectively, adopted low-dose imaging by directdetection electron-counting camera, successfully imaged the atomic structure of perovskite MAPbI3and discovered the degradation pathway of MAPbI3in detail.

Their study was published in Nature Communications.

Fig. 1 Atomic-imaging of the loss of MA+ and intermediate phase. (Image by SIAT)

Fig. 2 Atomic-scale imaging of the decomposition pathway. (Image by SIAT)

The researchers investigated the atomic structure via an imaging technique using a negative value of the spherical-aberration coefficient. As the dose increased, the intensity of MA+was decreased with the formation ofAt a certain dose, the intensity kept constant, indicating a relatively stable intermediate phase, MA0.5PbI3, which was verified by further TEM analysis and molecular dynamic simulation.

Consistent with the CL measurement, DFT calculations showed that the bandgap will increase as the MA vacancy’s density increases, which provided a potentially new strategy to tune the bandgap in constructing tandem solar cell and facilitated multiwave electroluminescence emission, adjusting various color luminescence under increasing bias voltage. With the discovery of the intermediate, the researcher further investigated the atomic-scale decomposition pathway of MAPbI3. At the first stage, theformed and the intermediate phasePbI3emerged. Consequent diffusion of Pb2+and I-intoand theoctahedron slipping from corner sharing to edge sharing makes the structure gradually evolve to PbI2.

This work can be used to guide the future TEM characterizations, enrich the understanding of the degradation mechanism and optimization strategies, and provide atomic-scale insights into understanding its fundamental properties.

Media Contact:

ZHANG Xiaomin

Email:xm.zhang@siat.ac.cn

(SIAT)