Chiral Perovskite Nanoplatelets with Tunable Circularly Polarized Luminescence in the Strong Confinement Regime

Abstract

Chiral perovskite nanocrystals have emerged as an interesting chiral excitonic platform that combines both structural flexibility and superior optoelectronic properties. Despite several recent demonstrations of optical activity in various chiral perovskite nanocrystals, efficient circularly polarized luminescence (CPL) with tunable energies remains a challenge. The chirality imprinting mechanism as a function of perovskite nanocrystal dimensionality remains elusive. Here, atomically thin inorganic perovskite nanoplatelets (NPLs) are synthesized with precise control of layer thickness and are functionalized by chiral surface ligands, serving as a unique platform to probe the chirality transfer mechanism at the organic/perovskite interface. It is found that chirality is successfully imprinted into mono‐, bi‐, and tri‐layer inorganic perovskite NPLs, exhibiting tunable circular dichroism (CD) and CPL responses. However, chirality transfer decreases in thicker NPLs, resulting in decreased CD and CPL dissymmetry factors for thicker NPLs. Aided by large‐scale first‐principles calculations, it is proposed that chirality transfer is mainly mediated through a surface distortion rather than a hybridization of electronic states, giving rise to symmetry breaking in the perovskite lattice and spin‐split conduction bands. The findings described here provide an in‐depth understanding of chirality transfer and design principles for distorted‐surface perovskites for chiral photonic applications.

Influence of Material Properties on Surface Chemistry Induced Circular Dichroism in Halide Perovskite: Computational Insights

“…The increase in edge length resulted in an order of magnitude decrease in | g anisotropy | maximum . It has also been observed in colloidal perovskite nanoplatelets, where the CD anisotropy decreased by an order of magnitude when going from one to three octahedral layers with chiral methylphenyl ethylammonium surface ligands …”

Chirality of CsPbBr3 Nanocrystals with Varying Dimensions in the Presence of Chiral Molecules

“…11−15 In addition, the unique structural softness and prominent ionic bonding character of LHPs NCs may enhance chiroptical effects compared to conventional II−VI semiconductors. 13,16,17 The introduction of chirality into LHP nanostructures allows for the manipulation of the angular momentum of both charge carriers and photons, which in turn controls the optoelectronic functionality. Significant emphasis has been given to induce CPL in CsPbCl x Br y I 3−x−y NCs by directly synthesizing chiral αoctylamine as a surface ligand 18 and assembling initially achiral NCs within a chiral organogel.…”

“…Lead halide perovskite (LHPs) nanocrystals (NCs) have emerged as promising candidates for developing next-generation chiroptical devices. They are suitable for investigating chirality-mediated electro-optical phenomena compared to the conventional II–VI NCs due to their broad absorption cross-section, tunable band gap, long carrier lifetime, high PLQE, and excellent charge transport properties. − In addition, the unique structural softness and prominent ionic bonding character of LHPs NCs may enhance chiroptical effects compared to conventional II–VI semiconductors. ,, The introduction of chirality into LHP nanostructures allows for the manipulation of the angular momentum of both charge carriers and photons, which in turn controls the optoelectronic functionality. Significant emphasis has been given to induce CPL in CsPbCl x Br y I 3– x – y NCs by directly synthesizing chiral α-octylamine as a surface ligand and assembling initially achiral NCs within a chiral organogel. , To date, the chiroptical properties of LHPs have been extensively investigated in the three-dimensional (3D) perovskite structure, − but research in the low-dimensional regime (0D, 2D) is given less attention.…”

“…Significant emphasis has been given to induce CPL in CsPbCl x Br y I 3– x – y NCs by directly synthesizing chiral α-octylamine as a surface ligand and assembling initially achiral NCs within a chiral organogel. , To date, the chiroptical properties of LHPs have been extensively investigated in the three-dimensional (3D) perovskite structure, − but research in the low-dimensional regime (0D, 2D) is given less attention. The combination of quantum confinement effects, substantial spin–orbit coupling, and compositional tunability in low-dimensional LHPs NCs may provide a versatile platform for tuning and enhancing chiral emission intensity. , Lu et al have reported that chirality is effectively imparted onto mono-, bi-, and trilayered 2D LHPs nanoplatelets (NPLs) and concluded that chirality transfer diminishes as the NPLs become thicker . Achieving tunable chiral emission by varying the dimensions of CsPbBr 3 NCs remains unexplored and poses a significant challenge.…”

“…We used the same CHEA ligand concentration (100 mmol/L) to prepare R / S -CHEA-induced CsPbBr 3 NCs via the postsynthesis ligand modification. Notably, lower-dimensional NCs possess a greater surface-to-volume ratio, superior chemical flexibility, and enhanced surface reactivity compared to their bulk counterparts. , More molecules can be inserted into the perovskite framework of 0D NCs than 3D NCs. Our NMR results support this prediction.…”