Abstract
Deciphering the atomic and electronic structures of interfaces is key to developing state-of-the-art perovskite semiconductors. However, conventional characterization techniques have limited previous studies mainly to grain-boundary interfaces, whereas the intragrain-interface microstructures and their electronic properties have been much less revealed. Herein using scanning transmission electron microscopy, we resolved the atomic-scale structural information on three prototypical intragrain interfaces, unraveling intriguing features clearly different from those from previous observations based on standalone films or nanomaterial samples. These intragrain interfaces include composition boundaries formed by heterogeneous ion distribution, stacking faults resulted from wrongly stacked crystal planes, and symmetrical twinning boundaries. The atomic-scale imaging of these intragrain interfaces enables us to build unequivocal models for the ab initio calculation of electronic properties. Our results suggest that these structure interfaces are generally electronically benign, whereas their dynamic interaction with point defects can still evoke detrimental effects. This work paves the way toward a more complete fundamental understanding of the microscopic structure–property–performance relationship in metal halide perovskites.
Highlights
Metal halide perovskites (MHPs) are an emerging class of semiconductors with the chemical formula of ABX3, where A is a monovalent organic or metal cation, B is a divalent metal cation, and X is a halide ion.[1,2] These semiconductors can be processed into thin films at low temperatures using various methods, and their compositions and properties are highly tunable, demonstrating promising applications in various optoelectronics.[1]
Perovskite-based solar cells (PSCs) have experienced a swift increase in power conversion efficiencies (PCEs) in the past few years.[3]. This has been enabled by a great number of fundamental research works that involve revealing and tailoring internal interface structures in MHP thin films.[4−13] Previous studies concerning interfaces have mainly relied on conventional characterizations, such as optical spectroscopy, scanning electron microscopy, and scanning probe microscopy, with spatial resolutions limited to only micro-/nanometer scales.[1,14−18] In this regard, those apparent grain boundaries (GBs) are frequently the only internal interfaces visible in the studies, whereas a considerable density of intragrain interfaces (IGIs) has recently been confirmed to exist in MHPs.[19]
Details of the MHP synthesis and perovskite-based solar cells (PSCs) fabrication are included in the Experimental Section
Summary
Metal halide perovskites (MHPs) are an emerging class of semiconductors with the chemical formula of ABX3, where A is a monovalent organic or metal cation, B is a divalent metal cation, and X is a halide ion.[1,2] These semiconductors can be processed into thin films at low temperatures using various methods, and their compositions and properties are highly tunable, demonstrating promising applications in various optoelectronics.[1]. With higher-level FA incorporation, does the average lattice spacing c keep increasing (Figure 2d−f) and the in-plane strain (εxx) distribution becomes more uneven with larger variations at the nanoscale (Figure 2g−i) This indicates a higher density of FA-rich clusters, as well as strained intragrain composition-boundary interfaces in FA-Cs perovskites with a FA cation content, that exceeds 50 mol %, when we examined a range of compositions (15−85 mol %). According to the STEMHAADF simulation (Figure S12), the intensity variation of FA/Cs and I columns shown in Figure 2c may imply an increase in FA incorporation from about 15 mol % to 40 mol % across the composition−boundary interface Another important finding is the observed fine structures of intragrain stacking faults in MHPs. In orthorhombic FA0.5Cs0.5PbI3 grains projected along the [100]o direction (Figure S13), a typical kind of stacking fault formed by lattice plane displacement was identified (Figure 3a).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
