Abstract
In two-dimensional (2D) chiral metal-halide perovskites (MHPs), chiral organic spacers induce structural chirality and chiroptical properties in the metal-halide sublattice. This structural chirality enables reversible crystalline-glass phase transitions in (S-NEA)2PbBr4, a prototypical chiral 2D MHP where NEA+ represents 1-(1-naphthyl)ethylammonium. Here, we investigate two distinct spherulite states of (S-NEA)2PbBr4, exhibiting either radial-like or stripe-like banded patterns depending on the annealing conditions of the amorphous film. Despite similarities in optical absorption and photoluminescence, the stripe-like, banded spherulite exhibits higher crystallinity and improved optical transparency compared to those of radial-like spherulite. X-ray nanoprobe measurements reveal tilting-angle modulations in the octahedral plane of stripe-like spherulites, correlating with the film’s surface geometry. Transfer matrix calculations indicate that the optical contrast in stripe-like patterns, seen in bright-field optical microscopy, arises from optical interference effects, differing from the contrast mechanism observed in polymer spherulites. Ultrafast carrier dynamics experiments suggest that the stripe-like spherulites resemble single crystals more closely than radial-like spherulites, while electrical conductivity measurements show enhanced charge carrier transport in stripe-like spherulites. These findings offer insights into MHP spherulite states with a single composition but different morphologies, previously observed only in polymers, highlighting their potential for optoelectronic applications.
| Original language | English |
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| Journal | Journal of the American Chemical Society |
| DOIs | |
| State | Accepted/In press - 2025 |
Funding
This work was primarily supported by the National Science Foundation under Grant No. CHE-2305138. This research used resources of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. Research conducted at the Center for High-Energy X-ray Science (CHEXS) is supported by the NSF (BIO, ENG and MPS Directorates) under award DMR-1829070. The cathodoluminescence measurement was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. The device fabrication for electrical measurements was carried out in the Singh Center for Nanotechnology at the University of Pennsylvania, which is supported by the NSF National Nanotechnology Coordinated Infrastructure Program under grant NNCI-2025608. D.J. and B.C. acknowledge support from the Office of Naval Research Young Investigator Award from Metamaterials Program (N00014-23-1-203). We acknowledge Judy Cha and Mehrdad Toussi Kiani at Cornell University and Shize Yang at Yale University for electron-beam diffraction experiments, Mengkun Liu at Stony Brook University for infrared nanospectroscopy experiments, and Omer Yaffe at Weizmann Institute of Science for low-frequency Raman spectroscopy measurements.