Hybrid perovskite crystals have emerged as an important class of semiconductors because of their remarkable performance in optoelectronics devices. The interface structure and chemistry of these crystals are key determinants of the device's performance. Unfortunately, little is known about the intrinsic properties of the surfaces of perovskite materials because extrinsic effects, such as complex microstructures, processing conditions, and hydration under ambient conditions, are thought to cause resistive losses and high leakage current in solar cells. We reveal the intrinsic structural and optoelectronic properties of both pristinely cleaved and aged surfaces of single crystals. We identify surface restructuring on the aged surfaces (visualized on the atomic-scale by scanning tunneling microscopy) that lead to compositional and optical bandgap changes as well as degradation of carrier dynamics, photocurrent, and solar cell device performance. The insights reported herein clarify the key variables involved in the performance of perovskite-based solar cells and fabrication of high-quality surface single crystals, thus paving the way toward their future exploitation in highly efficient solar cells.
KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: King Abdullah University of Science and Technology (KAUST) supported the work reported here. The authors gratefully acknowledge funding support from KAUST and from King Abdul-Aziz City for Science and Technology, Technology Innovation Center for Solid-State Lighting at KAUST. We also acknowledge Ahmed M. El-Zohry and Chen Yang for their help in the discussions related to reabsorption and crystal synthesis.