Inverted and Amplified CP-EL Behavior Promoted by AIE-Active Chiral Co-Assembled Helical Nanofibers

Circularly Polarized Luminescence Inversion Induced by Achiral Dyes in Organogels

Supramolecular assembly strategy is widely applied to develop circularly polarized luminescence (CPL) materials, especially for centrally chiral systems. The CPL sign of supramolecular gels based on a centrally chiral compound is generally regulated by employing the opposite chiral enantiomers. However, controlling CPL signals by regulating the interaction model between the achiral fluorophore and chiral gelator, accompanied by the adjustment of the emission wavelength, remains challenging. Herein, we have developed binary supramolecular gels based on achiral cyanostilbene derivatives and a chiral gelator. Two binary supramolecular gels have displayed achiral fluorophore-induced CPL sign inversion, attributed to the hydrogen bonding interaction between the carboxyl group of two fluorophores and the amino group of chiral gelator. This work reveals a rational approach to the design of CPL material with tunable CPL sign and CPL emission wavelength.

Hierarchical Chirality Transfer and Amplification within Conjugated Helical Polymers for Efficient Circularly Polarized Organic Light-Emitting Diodes and Photodetectors

Circularly polarized organic light-emitting diodes (CP-OLEDs) and CP photodetectors have received enormous attention owing to their promising potential in CP light-related technologies. The simultaneous construction of efficient CP-OLEDs and CP photodetectors using the multifunctionality of the same chiral material remains to be explored. Herein, achiral conjugated polymer poly(9,9-dioctylfluorene) (PFO) is used for coassembly with chiral helical polyacetylenes. The resulting chiral emitters can achieve high-performance circularly polarized electroluminescence (CPEL) with a large electroluminescence dissymmetry factor (gEL) of 0.11 and a high brightness of 9035 cd m-2. By introducing a flexible substrate into the device, flexible CP-OLEDs are realized. Additionally, such chiral emitters can serve as the photoactive layer of a CP photodetector to detect CP light, with a maximum photocurrent dissymmetry factor (gph) of the order of 10-1. This work provides a promising route to realize CP-OLEDs and CP photodetectors with large dissymmetry factors using polyfluorene and chiral polymer, facilitating their comprehensive and versatile development.

Recent Advances in Self-Assembled Naphthalimides: From Molecular Design to Applications

Naphthalimide-based self-assembled materials have gained significant attention in recent years because of their exceptional versatility and wide range of applications, from sensors and electronics to biomedical. Naphthalimides derivatives, with ease of functionalization and robust photophysical properties, became an ideal platform for creating highly ordered self-assembled architectures with tailored functionalities. This review provides an overall understanding of the recent developments in the synthesis and self-assembly of naphthalimide-based materials, focusing on how self-assembly enhances their performance in various applications. The review examines the role of self-assembly in improving these materials' optical, mechanical, and electronic properties, highlighting their use in sensors for detecting gases, volatile organic compounds (VOCs), and amines. Furthermore, the integration of self-assembled naphthalimides in light-emitting devices, energy-harvesting systems, and fluorescence-based imaging demonstrates their potential in both electronic and biological applications. By analyzing recent developments in molecular design, self-assembly strategies, and applications, this review aims to offer insights into how these materials can be optimized for future technological advancements.

Circularly polarized light emission from encapsulated aggregation-induced emission achiral luminogen within the supramolecular helical nanofilament networks

Circularly polarized light emission (CPLE) materials have attracted considerable attention owing to their broad range of potential applications, including spintronics. In this study, we introduce an innovative approach to impart CPLE activity to achiral aggregation-induced emission luminogens (AIEgens) by leveraging the nanoscale spontaneous phase separation between rod-like AIEgens and helical filaments formed by bent-core molecules. This phase separation was confirmed by transmittance analysis, X-ray diffraction, and other techniques as supported by transmission electron microscopy. Intrinsically, CPLE-inactive AIEgens aggregate in nanosized spaces, isolated from the helical filament network, and become CPLE-active via chirality transfer from the helical filaments. Thus, CPLE emission was achieved from the AIEgens encapsulated within the supramolecular helical nanofilament networks. The CPLE properties were significantly influenced by the size of the nanospace occupied by the AIEgens between the helical filament networks, as evaluated using scanning electron microscopy. This nanospace created a chiral environment, allowing the chirality of the helical filaments to transfer to the AIEgens during aggregation, rendering them CPLE-active. This study presents a universal strategy for fabricating CPLE materials without the need for complex chemical synthesis or the molecular design of luminogens.

Axially Chiral TADF Imidazolium Salts for Circularly Polarized Light-Emitting Electrochemical Cells

A pair of axially chiral thermally activated delayed fluorescent (TADF) enantiomers, R-TCBN-ImEtPF6 and S-TCBN-ImEtPF6, with intrinsic ionic characteristics were efficiently synthesized by introducing imidazolium hexafluorophosphate to chiral TADF unit. The TADF imidazolium salts exhibited a high photoluminescence quantum yield (PLQY) of up to 92 %, a small singlet-triplet energy gap (▵EST) of 0.04 eV, as well as reversible redox properties. Furthermore, the enantiomers showed distinct mirror-image CD and CPL activities with glum values of -3.7×10-3 and +3.4×10-3. Notably, by doping the axial TADF imidazolium salts into achiral TADF sensitizer, sandwich-structured light-emitting electrochemical cells (LECs) without the addition of ionic liquids (ILs) or ionic transition-metal compounds (iTMCs) were fabricated. When driven at 50 A m-2, the LECs displayed an EQE of up to 5.2 % and strong circularly polarized electroluminescence (CPEL) with gEL values of +3.3×10-3 and -3.0×10-3. This represents the first CP-LEC based on TADF materials and offers a promising strategy for the development of high-performance CPEL devices.

Constructing High-Performance Composite Epoxy Resins: Interfacial π-π Stacking Interactions-Driven Physical Rolling Behavior of Silica Microspheres

The intrinsic compromise between strength and toughness in composite epoxy resins significantly constrains their practical applications. In this study, a novel strategy is introduced, leveraging interfacial π-π stacking interactions to induce the "rolling behavior" of microsphere fillers, thereby facilitating efficient energy dissipation. This approach is corroborated through theoretical simulations and experimental validation. The resulting composite epoxy resin demonstrates an impressive 49.8% enhancement in strength and a remarkable 358.9% improvement in toughness compared to conventional epoxy resins, accompanied by substantially reduced hysteresis. Moreover, this system achieves reversible closed-loop recyclability and rapid repair capabilities. The preliminary demonstration of "force-temperature equivalence" further establishes a novel pathway for the design of high-performance composite epoxy materials.

Circularly Polarized Organic Light-Emitting Diode Based on Device Functional Layer Materials

Circularly polarized light-emitting devices have found extensive application prospects in 3D displays and optoelectronic information. Among them, circularly polarized organic light-emitting diodes (CP-OLED), as a rising star of circularly polarized light-emitting devices, achieved good research results. However, the preparation of CP-OLED with a high electroluminescence asymmetry factor and high external quantum efficiency is a hot and difficult research topic. At present, the approaches for achieving circularly polarized electroluminescence via CP-OLED are: 1) Using chiral materials as luminescent materials, 2) Utilizing chiral functional materials. This review summarizes recent methodologies used for manufacturing CP-OLED. It focuses on the construction strategies and applications of chiral functional materials (chiral host materials, chiral hole transport materials, and chiral electron transport materials) in CP-OLED. While challenges such as complex chiral design and material interactions persist, advancements in material design and device architecture propel CP-OLED forward. These developments promise to elevate CP-OLED as a focal point in optoelectronic research, facilitating high-performance, circularly polarized luminescence (CPL)-capable devices for practical applications.

Tunable circularly polarized electroluminescence behaviors from chiral co-assembled conjugated liquid crystal polymers

Chiral co-assembly strategy has proven effective in increasing the dissymmetry factor (gEL) of the emitting layers (EMLs) in circularly polarized organic light-emitting diodes (CP-OLEDs). Therefore, it is crucial to investigate the molecular structures that facilitate chiral co-assembly for further amplification of circularly polarized electroluminescence (CP-EL) signals. In this study, three types of achiral conjugated liquid crystal (LC) polymers (PFPh, PFNa and PFPy) and chiral binaphthyl-based polymer inducers (R/S-FO) were synthesized to construct corresponding chiral co-assemblies (R/S-FO)0.1-(PFPh/Na/Py)0.9 as EMLs for CP-OLEDs through strong intermolecular π-π stacking interactions. Interestingly, these resulting chiral co-assembled EMLs exhibited tunable CP-EL behaviors caused by the different conjugation linkers of LC polymers. Among them, the deep blue devices based on (R/S-FO)0.1-(PFNa)0.9 emitted the strongest CP-EL signals (|gEL| = 0.014, Lmax = 3039 cd m-2, CEmax = 1.16 cd A-1). It is attributed to the formation of ordered helical nanofibers facilitated by the excellent intermolecular compatibility due to the same naphthyl moieties in PFNa and R/S-FO. This study provides novel perspectives for developing high-performance CP-EL materials in chiral co-assembly systems.

Multicolor and sign-invertible circularly polarized luminescence from nonchiral charge-transfer complexes assembled with N-terminal aromatic amino acids

Circularly polarized luminescence (CPL) materials with precisely controlled emission colors and handedness are highly desirable for their promising applications in advanced optical technologies, but it is rather challenging to obtain them primarily due to the lack of convenient, powerful, and universal preparation strategies. Herein, we report a simple yet versatile solution route for constructing multicolor CPL materials with controllable handedness from nonchiral luminescent charge-transfer (CT) complexes through co-assembly with chiral N-terminal aromatic amino acids. The resulting ternary co-assemblies exhibit obvious CPL signals from 489 to 601 nm, covering from blue via green and yellow to orange-red. Notably, the CPL sign can be readily inverted by changing the substituents at the α-position of amino acids or the molecular structure of achiral electron donors due to effects on the hydrogen bonds, CT interactions, and stacking patterns. This work provides a new insight into developing CPL materials with tunable color and inverted handedness.

Self-Assembled Chiral Polymers Exhibiting Amplified Circularly Polarized Electroluminescence

Circularly polarized electroluminescence (CPEL) is highly promising in realm of 3D display and optical data storage. However, designing a groundbreaking chiral material with high comprehensive CPEL performance remains a formidable challenge. In this work, a pair of chiral polymers with self-assembled behavior is designed by integrating a chiral BN-moiety into polyfluorene backbone, named R-PBN and S-PBN, respectively. The chiral polymers show narrowband emission centered at 490 nm with full-width half maximum (FWHM) of 29 nm and high photoluminescence quantum yield (PLQY) of 79 %. After thermal annealing treatment, the chiral polymers undergo self-assembly, exhibiting amplified circularly polarized luminescence (CPL) with asymmetry factor (|glum|) of up to 0.11. Moreover, the solution-processed nondoped CP-OLEDs based on the chiral polymers as emitting layers exhibit maximum external quantum efficiency (EQEmax) of 9.8 %, intense CPEL activities with |gEL| of up to 0.07, and small FWHM of 36 nm, simultaneously. This represents the first case of self-assembled chiral polymers that combines high EQE, large gEL value and narrowband emission.

Intense Circularly Polarized Luminescence Induced by Chiral Supramolecular Assembly: The Importance of Intermolecular Electronic Coupling

Herein we report on circularly polarized luminescence (CPL) emission originating from supramolecular chirality of organic microcrystals with a |glum| value up to 0.11. The microcrystals were prepared from highly emissive difluoroboron β-diketonate (BF2dbk) dyes R-1 or S-1 with chiral binaphthol (BINOL) skeletons. R-1 and S-1 exhibit undetectable CPL signals in solution but manifest intense CPL emission in their chiral microcrystals. The chiral superstructures induced by BINOL skeletons were confirmed by single-crystal XRD analysis. Spectral analysis and theoretical calculations indicate that intermolecular electronic coupling, mediated by the asymmetric stacking in the chiral superstructures, effectively alters excited-state electronic structures and facilitates electron transitions perpendicular to BF2bdk planes. The coupling increases cosθμ,m from 0.05 (monomer) to 0.86 (tetramer) and triggers intense optical activity of BF2bdk. The results demonstrate that optical activity of chromophores within assemblies can be regulated by both orientation and extent of intermolecular electronic couplings.

Efficient helical columnar emitters of chiral homoleptic Pt(ii) metallomesogens for circularly polarized electroluminescence

Chiral organometallic Pt(ii) complexes have been demonstrated to be excellent circularly polarized luminescence (CPL) materials due to their rich phosphorescence and strong self-assembly characteristics. However, it remains a formidable task to simultaneously achieve high luminance (L) and electroluminescence dissymmetry factor (g EL) values for circularly polarized electroluminescence (CP-EL) devices of Pt(ii) complex-based emitters. In this study, we carry out a straightforward and efficient protocol to construct highly CPL-active helical columnar () emitters by using chiral homoleptic triazolatoplatinum(ii) metallomesogens (R/S-HPt). The peripheral flexible groups can not only improve solubility but also favor the induction of chirality and liquid crystal behavior. The resultant complexes R/S-HPt can self-assemble into the mesophase over a broad temperature range (6-358 °C) and exhibit excellent phosphorescence (Φ: up to 86%), resulting in intense CPL signals after thermal annealing (λ em = 615 nm and |g em| = 0.051). Using emitting layers (EML) based on R/S-HPt in solution-processed CP-EL devices, L max and |g EL| of CP-EL can reach up to 11 379 cd m-2 and 0.014, respectively. With comprehensive consideration of L max and g EL, this investigation shows the excellent performances among Pt(ii) complex-based CP-EL devices.

Chiral Co-Assembly with Narrowband Multi-Resonance Characteristics for High-Performance Circularly Polarized Organic Light-Emitting Diodes

A promising kind of ternary chiral co-assemblies with high PLQY, large dissymmetry factor (glum), and narrowband multi-resonance characteristics are achieved by codoped-thermal annealing treatments of achiral luminescent polymer F8BT, chiral inducers R/S-5011, and achiral FRET acceptor DBN-ICZ. The optimized co-assemblies (F8BT)0.9-(R/S-5011)0.1-(DBN-ICZ)0.005 display narrowband yellow emission with full-width half maximum (FWHM) of 37 nm, PLQY of 79%, and intense CPL signals with |glum| of up to 0.26. Meaningfully, solution-processed CP-OLEDs by using those ternary chiral co-assemblies as emitting layer are successfully fabricated, which display yellow circularly polarized electroluminescence (CPEL) with EQEmax of 4.6% and gEL of up to 0.16. The corresponding Q-factor could reach up to 7.36 × 10-3, which is the highest of all the reported CP-OLEDs. Moreover, the devices also exhibit excellent comprehensive device performance with low Von of 7.0 V, high Lmax of about 25 000 cd m-2, extremely low efficiency roll-off with EQE of 4.3% at 10 000 cd m-2, as well as narrowband EL with FWHM of only 39 nm. The proposed ternary co-assembly strategy in fabricating CP-OLED provides the possibility to achieve high comprehensive device performance such as balancing high EQE and large gEL value, as well as narrowband emission, high brightness and low efficiency roll-off simultaneously.

Aggregation-induced enhanced fluorescence emission of chiral Zn(II) complexes coordinated by Schiff-base type binaphthyl ligands

A pair of novel chiral Zn(II) complexes coordinated by Schiff-base type ligands derived from BINOL (1,1'-bi-2-naphthol), R-/S-Zn, were synthesized. X-ray crystallography revealed the presence of two crystallographically independent complexes; one has a distorted trigonal-bipyramidal structure coordinated by two binaphthyl ligands and one disordered methanol molecule (molecule A), while the other has a distorted tetrahedral structure coordinated by two binaphthyl ligands (molecule B). Numerous CH⋯π and CH⋯O interactions were identified, contributing to the formation of a 3-dimensional rigid network structure. Both R-/S-Zn exhibited fluorescence in both CH2Cl2 solutions and powder samples, with the photoluminescence quantum yields (PLQYs) of powder samples being twice as large as those in solutions, indicating aggregation-induced enhanced emission (AIEE). The AIEE properties were attributed to the restraint of the molecular motion arising from the 3-dimensional intermolecular interactions. CD and CPL spectra were observed for R-/S-Zn in both solutions and powders. The dissymmetry factors, gabs and gCPL values, were within the order of 10-3 to 10-4 magnitudes, comparable to those reported for chiral Zn(II) complexes in previous studies.

Amplified Circularly Polarized Luminescence Behavior in Chiral Co-assembled Liquid Crystal Polymer Films via the Strategic Manipulation of Chiral Inducers

One of the most important factors for the future application of circularly polarized luminescence (CPL) materials is their high dissymmetry factors (gem), and more and more studies are working tirelessly to focus on increasing the gem value. Herein, we chose an achiral liquid crystal polymer (LC-P) and two chiral binaphthyl-based inducers (R/S-3 and R/S-6) with different substitution positions (3,3' positions for R/S-3 and 6,6' positions for R/S-6) to construct chiral co-assemblies and explored their induced amplification CPL behaviors. Interestingly, after the thermal annealing treatment, this kind of chiral co-assembly (R/S-3)0.05-(LC-P)0.95 can emit a superior CPL signal (|gem| = 0.31 and λem = 424 nm), which achieves about 13-fold signal amplification in the spin-coated film, compared to (R/S-6)0.1-(LC-P)0.9 (|gem| = 0.023 and λem = 424 nm). This is because (R/S-3)0.05-(LC-P)0.95 could further co-assemble to form a more ordered arrangement LC state and generate regular helix nanofibers than that of (R/S-6)0.1-(LC-P)0.9. This work provides an efficient method for synthesizing high-quality CPL-active materials through the strategic manipulation of the structure of chiral binaphthyl-based inducers in chiral co-assembled LCP systems.

Strong Circularly Polarized Luminescence Promoted by AIE-active Chiral Co-assemblies in Liquid Crystal Polymer Films

Recently, extensive works have focused on increasing the dissymmetry factors (glum) of various circularly polarized luminescence (CPL) materials, which is one of the most important factors for future applications of CPL. Herein, we designed a chiral co-assembled liquid crystal polymer (LCP) PTZ@R/S-PB2, which was prepared by chiral binary co-polymer (R/S-PB2) doped with achiral phenothiazine derivation dye (PTZ). For comparison, ternary co-polymerized LCP (R/S-PT) was synthesized by co-polymerizing with mesogenic monomer, chiral monomer and emissive monomer. Both PTZ@R/S-PB2 and R/S-PT showed aggregation-induced emission (AIE) properties. Interestingly, the CPL signals of both PTZ@R/S-PB2 and R/S-PT were reversed and amplified after thermal annealing treatment. The |glum| values of the co-assembled PTZ@R/S-PB2 were up to 0.13 at a 32 nm thickness, which was 5.4 times that of R/S-PT (|glum|=0.024). This is due to PTZ@R/S-PB2 could form more orderly chiral co-assembly structures. Noticeably, increasing the LCP film thickness could further improve the glum value, and the maximum glum of PTZ@R/S-PB2 could be enhanced to +0.91/-0.82 at a 220 nm thickness.

Chiral TPE Foldamers in Macrocycles: Aggregation Enhanced Emission and Circularly Polarized Luminescence

Chiral macrocycles with circularly polarized luminescence (CPL) have attracted increasing attention due to the rigid structure, symmetrical chiral geometry and large luminescence dissymmetry factors (glum ). However, most chiral macrocycles are more emissive in solutions but have weakened fluorescence quantum yields (ΦF ) in aggregates, limiting their further application. In this paper, chiral macrocycle R/S-PhTPE was synthesized by combining chiral macrocycle architectonics with Z-o-phenyltetraphenylethylene (PhTPE) foldamer. Enhanced solution state emission and characteristic aggregation enhanced emission (AEE) effect can be observed for R/S-PhTPE due to the folded PhTPE conformation. Macrocycle immobilization and folded conformation endow PhTPE moiety with stable helical conformation. Most importantly, R/S-PhTPE exhibits opposite CPL signals compared with common chiral TPEs, demonstrating the evident impact of folded conformation. This work reports the first and deep insights into the chiroptical properties of chiral PhTPE foldamers, and will provide a new strategy to tune ΦF and CPL signals of AIE active chiral macrocycles.