Spatially Correlated Chirality in Chiral Two-Dimensional Perovskites Revealed by Second-Harmonic-Generation Circular Dichroism Microscopy

Abstract

Understanding the chiral mechanism of chiral hybrid perovskites is a prerequisite for developing relevant chiroptoelectronic applications. Although conventional circular dichroism (CD) spectroscopy can be used to characterize chirality in chiral perovskites, it has a low signal-to-noise ratio and can provide only information about macroscopic chirality. Herein, with the aim of revealing the microscopic chiral mechanism in chiral perovskites, we utilize a spacer cation alloying strategy to construct chiral two-dimensional perovskites. For the first time, we demonstrate second-harmonic-generation CD microarea imaging in chiral perovskite thin films to unveil their spatially correlated chirality. In combination with theoretical calculations, it is revealed that the spatially correlated chirality is caused by localized out-ofplane supramolecular orientations. This work will not only advance the understanding of the mechanism of chiroptical activity in chiral perovskites but also provide inspiration for the rational design and synthesis of perovskites for chirality-related nonlinear optoelectronic devices.

Optical Second Harmonic Generation of Low-Dimensional Semiconductor Materials

“…This concept has been extensively investigated across a range of cutting-edge applications. Chiral hybrid perovskites, as a novel class of chiral semiconductors, have demonstrated significant potential in the realm of nonlinear optics, particularly in SHG [ 20 , 21 , 178 , 179 , 180 , 181 ]. For instance, Dongying Fu [ 182 ] and coworkers investigated the SHG-circular dichroism (SHG-CD) effect in chiral 1D [( R / S )-3-aminopiperidine]PbI 4 bulk single crystals.…”

“…Copyright © 2023 American Chemical Society. ( g ) Crystal structures of chiral 2D R - and S - MBPB perovskites [ 179 ]. ( h , i ) SHG intensity variation in R - and S - MBPB perovskites under different excitation wavelengths from 780 to 900 nm.…”

Chirality Extends Multiple-Channel Bistable Responses in Hybrid Perovskites

“…Chiral isomerism, as two configurations of molecules, is usually mirror symmetric and can exhibit completely different activities in chiral optics. 52 Emphatically, both (R-3-OHpyl)-PbBr 3 and (S-3-OHpyl)PbBr 3 with chiral organic cations crystalline in the chiral space group (P2 1 2 1 2 1 ), thereby activating the chiroptical activity (circular dichroism; see Figure 4d) of the enantiomers. As shown in Figure 4e, the CD spectra of enantiomers exhibit a mirror symmetric CD signal at 290 nm, indicating that two hybrid perovskites with homochiral organic cations possess bistability in optical properties.…”

“…Chiral isomerism, as two configurations of molecules, is usually mirror symmetric and can exhibit completely different activities in chiral optics . Emphatically, both ( R -3-OHpyl)­PbBr 3 and ( S -3-OHpyl)­PbBr 3 with chiral organic cations crystalline in the chiral space group ( P 2 1 2 1 2 1 ), thereby activating the chiroptical activity (circular dichroism; see Figure d) of the enantiomers.…”

Lead-Free Chiral Perovskite for High Degree of Circularly Polarized Light Emission and Spin Injection

“…Chiral perovskites are essential in the application of circularly polarized light (CPL) sources and spintronics. − Chiral perovskites are constructed by incorporating chiral molecules into achiral inorganic perovskite framework, in which the chirality can transfer from molecules to perovskites and then chiroptical activity emerges. ,− Although significant progress has been made in CPL emission based on chiral perovskites, most of them are toxic lead-based perovskites, ,− which is harmful to human and environment and constrains their practical applications. Several groups have demonstrated CPL of lead-free chiral perovskites using hybrids of Mn, Cu, Sn, and so on. − However, the highest degree of circular polarization (DOCP) of all the reported lead-free chiral perovskites is 0.5% to the best of our knowledge, which is due to all those lead-free chiral perovskites being dominated by self-trapped exciton (STE) emission, and thus the spin relaxation reduces DOCP dramatically .…”