Direct Detection of Near-Infrared Circularly Polarized Light via Precisely Designed Chiral Perovskite Heterostructures

Orientation-Driven Chirality Funnels in Chiral Low-Dimensional Lead-Halide Perovskite Heterostructures

Chiral hybrid metal-halide perovskites show low-symmetry crystal structures, large Rashba splitting, spin-filtering, and strong chiroptical activity. Circular dichroism and circularly polarized photoluminescence have been investigated in chiral perovskites with increasingly distorted chiral structures. Here, we report the fabrication of chiral (R/S)-EBAPbI3 (EBA = α-ethylbenzylamine) single crystals, which possess highly distorted octahedral structures with a high angle variance value of ∼68 degree2. Using control in the fabrication conditions, we transfer chiral single crystals to thin films and achieve different crystal orientation preferences that induce tunable chiroptical properties to their heterostructures with PbI2 nanodomains, which we characterize with in situ X-ray diffraction and grazing-incidence wide-angle X-ray scattering measurements. Using transient chiroptical spectroscopies, we resolve photoexcited charge carrier dynamics and chirality transfer processes in such heterostructures down to cryogenic temperatures. We observe rapid carrier transfer along the in-plane (002) facets in chiral perovskite phases to PbI2 nanostructures within the initial few picoseconds, while carrier transfer along the out-of-plane (002) facets occurs at a slower rate. This fast transfer process leads to high photoluminescence intensities and large degrees of circular polarization in the emission from PbI2 nanodomains at cryogenic temperatures. Our findings report a multidimensional chiral-achiral heterostructure which takes advantage of controllable chirality transfer and offers new routes for future spintronic and chiroptical applications.

Enantioselective Se lattices for stable chiroptoelectronic processing media

Chiroptoelectronic devices are crucial for applications in quantum computing, spin optical communications, and magnetic recording. However, the limited efficiency and low stability of conventional circularly polarized light (CPL)-sensing materials have restricted their broader use. Here, we introduce atomic chiral Se nanorod (NRs) films as broadband CPL detectors, leveraging the intrinsic chirality and stability of Se nanocrystals. We also perform incident circular polarization (ICP)-Raman optical activity (ROA) to explore the chiroptical activity of the large-area films. The Se NRs thin films detected CPL across a broad range from ultraviolet (UV) to short-wavelength infrared (SWIR), with a responsivity dissymmetry factor of up to 0.4, maintaining high stability under ambient conditions for longer than 13 months. CPL-sensitive Se NRs with intrinsic chirality have potential applications in chiral photonic synapses, chiral spin devices, and CPL-sensitive photocatalysts. ICP-ROA mapping also advances the analysis of 2D chiral materials.

Chirality-Induced Spin Selectivity in Hybrid Organic-Inorganic Perovskite Semiconductors

The movement of charges through a chiral medium results in a spin-polarized charge current. This phenomenon, known as the chirality-induced spin selectivity (CISS) effect, enables control over spin populations without the need for magnetic components and operates at room temperature. CISS has been discovered in a range of chiral media and most prominently studied in chiral organic molecular species. Chiral hybrid organic-inorganic perovskite semiconductors combine the unique and functional aspects of inorganic semiconductors with chiral molecules. The inorganic component borrows the homochirality of the organic component to yield a unique family of highly tunable chiral semiconductors, where the enantiomeric purity is defined by the organic component. Semiconductors already form the backbone of modern-day technologies. Adding chirality and control over spin through CISS provides new avenues for creative technological development. This review is intended to be an introduction to these unique systems and the demonstrations of CISS and spin control.

Chiral 2D and quasi-2D hybrid organic inorganic perovskites: from fundamentals to applications

Chiral 2D and quasi-2D hybrid organic-inorganic perovskites (HOIPs) are emerging as promising materials for a variety of applications principally related to optoelectronics and spintronics, thanks to the combined benefits deriving from both the chiral cation and the perovskite structure. Since its recent birth, this research field is tremendously growing, focalizing on the chemical composition tuning to unveil its influence on the related functional properties as well as on developing devices for practical applications. In this review, we focused on the properties of 2D and quasi-2D chiral HOIPs, firstly providing an overview on their chiroptical behaviour followed by their potential exploitation in devices investigated so far for various applicative fields.

Giant chiral amplification of chiral 2D perovskites via dynamic crystal reconstruction

Chiral hybrid perovskites show promise for advanced spin-resolved optoelectronics due to their excellent polarization-sensitive properties. However, chiral perovskites developed to date rely solely on the interaction between chiral organic ligand cations exhibiting point chirality and an inorganic framework, leading to a poorly ordered short-range chiral system. Here, we report a powerful method to overcome this limitation using dynamic long-range organization of chiral perovskites guided by the incorporation of chiral dopants, which induces strong interactions between chiral dopants and chiral cations. The additional interplay of chiral cations with chiral dopants reorganizes the morphological and crystallographic properties of chiral perovskites, notably enhancing the asymmetric behavior of chiral 2D perovskites by more than 10-fold, along with the highest dissymmetry factor of photocurrent (gPh) of ~1.16 reported to date. Our findings present a pioneering approach to efficiently amplify the chiroptical response in chiral perovskites, opening avenues for exploring their potential in cutting-edge optoelectronic applications.

Chiral Induced Spin Selectivity

Since the initial landmark study on the chiral induced spin selectivity (CISS) effect in 1999, considerable experimental and theoretical efforts have been made to understand the physical underpinnings and mechanistic features of this interesting phenomenon. As first formulated, the CISS effect refers to the innate ability of chiral materials to act as spin filters for electron transport; however, more recent experiments demonstrate that displacement currents arising from charge polarization of chiral molecules lead to spin polarization without the need for net charge flow. With its identification of a fundamental connection between chiral symmetry and electron spin in molecules and materials, CISS promises profound and ubiquitous implications for existing technologies and new approaches to answering age old questions, such as the homochiral nature of life. This review begins with a discussion of the different methods for measuring CISS and then provides a comprehensive overview of molecules and materials known to exhibit CISS-based phenomena before proceeding to identify structure-property relations and to delineate the leading theoretical models for the CISS effect. Next, it identifies some implications of CISS in physics, chemistry, and biology. The discussion ends with a critical assessment of the CISS field and some comments on its future outlook.

Template-Assisted Synthesis of 2D Perovskite Grating Single Crystal Films at Low Temperatures for UV Polarization-Sensitive Photodetectors

2D perovskites have attracted tremendous attention due to their superior optoelectronic properties and potential applications in optoelectronic devices. Especially, the larger bandgap of 2D perovskite means that they are suitable for UV photodetection. However, the layered structure of 2D perovskites hinders the interlayer carrier transport, which limits the improvement of device performance. Therefore, nanoscale structures are normally used to enhance the light absorption ability, which is an effective strategy to improve the photocurrent in 2D perovskite-based photodetectors. Herein, a template-assisted low-temperature method is proposed to fabricate 2D perovskite ((C6 H5 C2 H4 NH3 )2 PbBr4 , (PEA)2 PbBr4 ) grating single crystal films (GSCFs). The crystallinity of the (PEA)2 PbBr4 GSCFs is significantly improved due to the slow evaporation of the precursor solution under low temperatures. Based on this high crystalline quality and extremely ordered microstructures, the metal-semiconductor-metal photodetectors are assembled. Finite-different time-domain (FDTD) simulation and experiment indicate that the GSCF-based photodetectors exhibit significantly improved performance in comparison with the plane devices. The optimized 2D perovskite photodetectors are sensitive to UV light and demonstrate a responsivity and detectivity of 28.6 mA W-1 and 2.4 × 1011 Jones, respectively. Interestingly, the photocurrent of this photodetector varies as the angle of the incident polarized light, resulting in a high polarization ratio of 1.12.

Low Detection Limit Circularly Polarized Light Detection Realized by Constructing Chiral Perovskite/Si Heterostructures

Chiral perovskites have been demonstrated as promising candidates for direct circularly polarized light (CPL) detection due to their intrinsic chirality and excellent charge transport ability. However, chiral perovskite-based CPL detectors with both high distinguishability of left- and right-handed optical signals and low detection limit remain unexplored. Here, a heterostructure, (R-MPA)2 MAPb2 I7 /Si (MPA = methylphenethylamine, MA = methylammonium) is constructed, to achieve high-sensitive and low-limit CPL detection. The heterostructures with high crystalline quality and sharp interface exhibit a strong built-in electric field and a suppressed dark current, not only improving the separation and transport of the photogenerated carriers but also laying a foundation for weak CPL signals detection. Consequently, the heterostructure-based CPL detector obtains a high anisotropy factor up to 0.34 with a remarkably low CPL detection limit of 890 nW cm-2 under the self-driven mode. As a pioneering study, this work paves the way for designing high-sensitive CPL detectors that simultaneously have great distinguishing capability and low detection limit of CPL.

Multifunctional Perovskite Photodetectors: From Molecular-Scale Crystal Structure Design to Micro/Nano-scale Morphology Manipulation

Multifunctional photodetectors boost the development of traditional optical communication technology and emerging artificial intelligence fields, such as robotics and autonomous driving. However, the current implementation of multifunctional detectors is based on the physical combination of optical lenses, gratings, and multiple photodetectors, the large size and its complex structure hinder the miniaturization, lightweight, and integration of devices. In contrast, perovskite materials have achieved remarkable progress in the field of multifunctional photodetectors due to their diverse crystal structures, simple morphology manipulation, and excellent optoelectronic properties. In this review, we first overview the crystal structures and morphology manipulation techniques of perovskite materials and then summarize the working mechanism and performance parameters of multifunctional photodetectors. Furthermore, the fabrication strategies of multifunctional perovskite photodetectors and their advancements are highlighted, including polarized light detection, spectral detection, angle-sensing detection, and self-powered detection. Finally, the existing problems of multifunctional detectors and the perspectives of their future development are presented.

Circularly Polarized Light Responsive Materials: Design Strategies and Applications

Circularly polarized light (CPL) with the end of optical vector traveling along circumferential trajectory shows left- and right-handedness, which transmits chiral information to materials via complicated CPL-matter interactions. Materials with circular dichroism respond to CPL illumination selectively with differential outputs that can be used to design novel photodetectors. Racemic or achiral compounds under CPL go through photodestruction, photoresolution, and asymmetric synthesis pathways to generate enantiomeric bias and optical activity. By this strategy, helical polymers and chiral inorganic plasmonic nanostructures are synthesized directly, and their intramolecular folding and subsequent self-assembly are photomodulable as well. In the aggregated state of self-assembly and liquid crystal phase, helical sense of the dynamic molecular packing is sensitive to enantiomeric bias brought by CPL, enabling the chiral amplification to supramolecular scale. In this review, the application-guided design strategies of CPL-responsive materials are aimed to be systematically summarized and discussed. Asymmetric synthesis, resolution, and property-modulation of small organic compounds, polymers, inorganic nanoparticles, supramolecular assemblies and liquid crystals are highlighted based on the important developments during the last decades. Besides, applications of light-matter interactions including CPL detection and biomedical applications are also referred.

Near-infrared polarization-sensitive photodetection via interfacial symmetry engineering of an Si/MAPbI3 heterostructural single crystal

Methylammonium lead iodide (MAPbI₃) single crystals (SCs) have drawn particular attention in the optoelectronics field, due to their outstanding photoelectric performance. However, the structures of those MAPbI₃ SCs are isotropic, which limits the further application of the materials for polarization-sensitive photodetection. Here, we propose a strategy of symmetry modulation by heterogeneously integrating large-sized MAPbI₃ SCs with silicon (Si) wafers and we give the first demonstration of self-powered near-infrared (NIR) polarization-sensitive photodetection using MAPbI₃ SCs. Created via a delicate solution method, the MAPbI₃/Si heterostructures show a high crystalline quality and a solid interfacial connection. More importantly, the built-in electric field resulting from the band bending at the MAPbI₃/Si heterostructure interface generates polar symmetry, which enables directional transport of photogenerated carriers, making the MAPbI₃/Si heterostructures highly polarization-sensitive. Consequently, in the self-powered mode, NIR photodetectors of MAPbI₃/Si heterostructures exhibit large polarization ratios of 3.3 at 785 nm and 2.8 at 940 nm. Moreover, a high detectivity of 7.35 × 10¹² Jones of the present devices is also achieved. Our work gives the first demonstration of self-powered polarization-sensitive photodetection of MAPbI₃ SCs and provides a strategy to design polarization-sensitive materials beyond the conventional limitations induced by isotropic structures.

Influence of Pd(II) Adsorption on High-Temperature Ferroelastic Phase Transition in (2-Amino-2-thiazolinium)PbBr3

Ferroelastic materials have received special attention because of their great promise for mechanical switches, piezoelectric sensors, and data storage applications. Here, we report a novel ferroelastic semiconducting hybrid organic-inorganic perovskite (C₃H₇N₂S)PbBr₃ (1) [(C₃H₇N₂S)⁺ is 2-amino-2-thiazolinium] with a ferroelastic phase transition at 395 K and an optical band gap of 3.43 eV. 1 has a one-dimensional BaNiO₃-type structure and undergoes a high-temperature ferroelastic phase transition with an Aizu notation of mmmF2/m. Meanwhile, 1 exhibits dielectric switch near the phase transition temperature. By introducing the thioether group, the motion of the molecules or ions of 1 is hindered after the sorption of Pd(II) metal ions, which leads to the disappearance of the high-temperature ferroelastic phase transition and dielectric switch. This is the first reported ferroelastic semiconductor material with Pd(II) adsorption property, by studying the influence of Pd(II) adsorption on high-temperature ferroelastic phase transition, it may be enlightening to further uncover the mechanism of phase transition or the origin of ferroelasticity, which represents an important step toward multifunctional applications of lead-hybrid perovskite-based ferroelastic materials.