Abstract
Ferroelasticity represents material domains possessing spontaneous strain that can be switched by external stress. Three-dimensional perovskites like methylammonium lead iodide are determined to be ferroelastic. Layered perovskites have been applied in optoelectronic devices with outstanding performance. However, the understanding of lattice strain and ferroelasticity in layered perovskites is still lacking. Here, using the in-situ observation of switching domains in layered perovskite single crystals under external strain, we discover the evidence of ferroelasticity in layered perovskites with layer number more than one, while the perovskites with single octahedra layer do not show ferroelasticity. Density functional theory calculation shows that ferroelasticity in layered perovskites originates from the distortion of inorganic octahedra resulting from the rotation of aspherical methylammonium cations. The absence of methylammonium cations in single layer perovskite accounts for the lack of ferroelasticity. These ferroelastic domains do not induce non-radiative recombination or reduce the photoluminescence quantum yield.
Highlights
Ferroelasticity represents material domains possessing spontaneous strain that can be switched by external stress
Solutions for BA2PbI4 (BAI-N1), BA2MAPb2I7 (BAI-N2), and BA2MA2Pb3I10 (BAI-N3) crystal growth were prepared by dissolving butylammonium iodide (BAI), methylammonium iodide (MAI), and lead iodide (PbI2), with respective molar ratios of 2:0:1, 2:1:2, and 2:2:3, in hydriodic acid (HI) at 130 °C
After inserting 150 μL precursor between two glass substrates (2 × 3 inches) at 130 °C, the growth temperature was gradually decreased to ~20 °C at a rate of 10 °C per h to produce thin layered perovskite crystals
Summary
Ferroelasticity represents material domains possessing spontaneous strain that can be switched by external stress. The absence of methylammonium cations in single layer perovskite accounts for the lack of ferroelasticity These ferroelastic domains do not induce non-radiative recombination or reduce the photoluminescence quantum yield. Using scanning photocurrent mapping and photoluminescence (PL) imaging, TBs were found to exhibit benign electronic behavior, i.e., neither blocking carrier transport across them nor introducing non-radiative recombination pathways. This benign nature indicates that ferroelasticity in MAPI can help relieve device stress[18] in processing and service, making them more flexible without sacrificing carrier transport or device performance
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