Layered Metal‐Halide Perovskite Single‐Crystalline Microwire Arrays for Anisotropic Nonlinear Optics

Abstract

Hybrid organic-inorganic metal-halide perovskites with diverse structure tunability are promising for nonlinear-optical (NLO) applications, such as frequency conversion and electro-optic modulation. For integrated NLO devices, single-crystalline perovskite micro-and nanostructures with high quality and multifunctionality are in high demand. However, the fabrication of singlecrystalline perovskites arrays is still challenging in regulating liquid dynamics and crystal growth simultaneously. Herein, a capillary-bridge-manipulated strategy is established to steer the dewetting process of microdroplets and provide spatial confinement for crystal growth. These 1D perovskite microwire arrays show regulated geometry, pure orientation, and single crystallinity. Chiral ammonium molecules are introduced into the metal-halide octahedral quantum wells to break the centrosymmetry of the perovskite, allowing the perovskite to exhibit excellent second-order NLO properties. The as-prepared microwire arrays also demonstrate linearly polarized second harmonic generation and two-photon fluorescence. Microwire arrays exhibit higher second harmonic conversion efficiency compared with their polycrystalline thin-film counterparts. It is believed that this strategy for the fabrication of chiral perovskite microstructure arrays holds great promise for NLO integrated applications and opens up an avenue to explore multifunctional chiral perovskites.

Thermally-driven unusual dual SHG switching with wide SHG-active steps triggered by inverse symmetry breaking

“…6,7 Benefitting from their reversible, controllable, and in situ SHG switching features, these kind of materials are considered to have great potential applications in optical devices as a light-sensor, environmental monitor, data storage, and optical communication carrier. 8,9 As solid-state "SHG switches", it should have at least two states, namely a noncentrosymmetric (NCS) state, and a centrosymmetric (CS) state. A reversible structural phase transition accompanied by SHG response meets the nature of this switch and the phase transition point is the crucial point that regulates the SHG signals.…”

Two-dimensional BA2PbBr4-based wafer for X-rays imaging application

“…25,26 Creatively, to overcome the unfavorable ion migration and poor stability, researchers introduced organic molecules into the perovskite structure to form a two-dimensional (2D) perovskite, in which lead halide octahedral sheets are separated by an organic spacer. [27][28][29][30][31][32][33] The organic spacer increases the activation energy of ion transport and therefore inhibits ion migration. 34,35 Furthermore, due to the steric hindrance produced by the organic spacer, it will increase the required for the phase transition to the non-perovskite phase, therefore improving the stability of the perovskite.…”

Hierarchically Ordered Perovskites with High Photo‐Electronic and Environmental Stability via Nanoimprinting Guided Block Copolymer Self‐Assembly

“…[21][22][23] The structural instability of HPs becomes pronounced as the pattern dimension decreases to the sub-100 nm scale as a result of the increased surface-to-volume ratio, making them significantly unstable in ambient conditions. Diverse unconventional patterning methods have been employed based on soft lithography, such as imprinting, [24,25] micromolding, [26,27] ink-jet printing, [28] capillary bridge method, [29] wettability surface control, [30,31] and micro/nanopumping, [32] giving rise to well-defined patterns of HPs on the micrometer and few-hundred-nanometer scales without harming their intrinsic photophysical properties. However, further scaling down of the pattern size to sub-100 nm is challenging because of the difficulty in not only controlling the crystallization of HPs in such small dimensions but also ensuring the environmental stability of the patterned crystals.…”