Elucidating the origin of chiroptical activity in chiral 2D perovskites through nano-confined growth

Abstract

Chiral perovskites are being extensively studied as a promising candidate for spintronic- and polarization-based optoelectronic devices due to their interesting spin-polarization properties. However, the origin of chiroptical activity in chiral perovskites is still unknown, as the chirality transfer mechanism has been rarely explored. Here, through the nano-confined growth of chiral perovskites (MBA2PbI4(1-x)Br4x), we verified that the asymmetric hydrogen-bonding interaction between chiral molecular spacers and the inorganic framework plays a key role in promoting the chiroptical activity of chiral perovskites. Based on this understanding, we observed remarkable asymmetry behavior (absorption dissymmetry of 2.0 × 10−3 and anisotropy factor of photoluminescence of 6.4 × 10−2 for left- and right-handed circularly polarized light) in nanoconfined chiral perovskites even at room temperature. Our findings suggest that electronic interactions between building blocks should be considered when interpreting the chirality transfer phenomena and designing hybrid materials for future spintronic and polarization-based devices.

Revealing the Intrinsic Chiroptical Activity in Chiral Metal-Halide Semiconductors

“…Generally, CD of chiral MHS is measured in the form of thin films, and the anisotropy factor is calculated (eq ), which is proposed to be thickness independent. Although thin films are convenient for CD measurements, the CD signals are inevitably interfered by linear dichroism (LD) and linear birefringence (LB), namely, <LD>, <LB> ≠ 0, due to macroscopic anisotropies in solid states.…”

“…However, the exact structural emergence of a high anisotropy factor for chiral MHS remains ambiguous, mainly resulting from a poor understanding of the macroscopic origin of CD mechanism. Generally, CD of chiral MHS is measured in the form of thin films, 30 and the anisotropy factor is calculated (eq 1), which is proposed to be thickness independent. Although thin films are convenient for CD measurements, the CD signals are inevitably interfered by linear dichroism (LD) and linear birefringence (LB), namely, <LD>, <LB> ≠ 0, due to macroscopic anisotropies in solid states.…”

Impact of crystal growth diversity on magneto-photoluminescence and circular dichroism in chiral lead halide perovskites

“…23 In order to achieve a decent CD, rational designs for crystallinities and phase arrangements may be required for solutionprocessable 2D chiral perovskites. [24][25][26][27] Analogously, these have been always concerned with conventionally achiral quasi-2D perovskites for high performance LEDs. [28][29][30] As we know, the crystallinities and phases are decisive for electronic structures, like dimensions, energy gaps and charge transport routes.…”

Two-Dimensional Chiroptically Active Copper Oxide Nanostructures

“…This is despite the fact that these materials are expected to demonstrate unique properties due to their high aspect ratio, special electronic confinement and specific structural deformations of 2D nanosheets. While there are several reports of chirality induction in 2D perovskites, research into other chiral 2D nanomaterials is limited. − For example, there is only one report on chiral graphene-based quantum dots, and one recent publication on the preparation of chiral 2D transition metal dichalcogenide (TMD) nanomaterials by carrying out liquid phase exfoliation of MoS 2 in the presence of chiral ligands (cysteine and penicillamine). , Induction of chirality in these colloidal 2D nanostructures can be achieved by synthesis with the chiral ligand present in situ, or by relatively straightforward postsynthetic ligand exchange reactions, replacing the achiral species with the chiral molecule of choice. − It is anticipated that these chiral 2D nanomaterials may find applications in exciting and rapidly developing research areas such as biotechnology and nanomedicine, as chirality plays an integral role in chemical and biological recognition …”