Concentrating aggregation-induced fluorescence in planar waveguides: a proof-of-principle

Carborane-Decorated Siloles with Highly Efficient Solid-State Emissions - What Drives the Photophysical Properties?

New hybrids were synthesised by linking carboranes and siloles, both of which are known as aggregation-induced emission active units. Although most of the newly synthesised systems do not display notable quantum yield either in solution or in the aggregated state, they emit strongly in the solid-state, and a quantum yield of up to 100 % can be achieved. The tailorable quantum yield can be attributed to the packing of the molecules in the crystal lattice ruled by the carborane and phenyl moieties according to the SC-XRD data. Our experimental results, complemented by density functional theory calculations, show that the silole moiety primarily influences the photophysical properties. At the same time, the carborane serves as a steric building block without direct responsibility for the aggregation-induced emission property. The patterns of substituents can alter the absorption and emission properties.

Substrate-Controlled [8 + 3] Cycloaddition of Tropsulfimides and Tropones with Zwitterionic Allenyl Palladium Species Derived from Vinylidenecyclopropane-diesters

A palladium-catalyzed regioselective [8 + 3] cycloaddition of tropsulfimides and tropones with vinylidenecyclopropane-diesters (VDCP-diesters) has been disclosed in this paper, affording decahydro-1H-cyclohepta[b]pyridine derivatives bearing an allene moiety or decahydro-1H-cyclohepta[b]pyran derivatives having a conjugated diene unit in moderate to good yields. The reactions proceed through a zwitterionic allenyl palladium species derived from VDCP-diesters. The substrate scopes have been investigated and the plausible reaction mechanisms have also been proposed according to the previous work, the first captured zwitterionic Pd-allenyl intermediate, and control experiments.

Aggregation-induced emissive nanoarchitectures for luminescent solar concentrators

Aggregation-induced emission (AIE), the phenomenon by which selected luminophores undergo the enhancement of emission intensity upon aggregation, has demonstrated potential in materials and biomaterials science, and in particular in those branches for which spectral management in the solid state is of fundamental importance. Its development in the area of luminescent spectral conversion devices like luminescent solar concentrators (LSCs) is instead still in its infancy. This account aims at summarizing relevant contributions made in this field so far, with a special emphasis on the design of molecular and macromolecular architectures capable of extending their spectral breadth to the deep-red (DR) and the near-infrared (NIR) wavelengths. Because of the many prospective advantages characterizing these spectral regions in terms of photon flux density and human-eye perception, it is anticipated that further development in the design, synthesis and engineering of advanced molecular and macromolecular DR/NIR-active AIE luminophores will enable faster and easier integration of LSCs into the built environment as highly transparent, active elements for unobtrusive light-to-electricity conversion.

Alkynylated and triazole-linked aroyl-S,N-ketene acetals: one-pot synthesis of solid-state emissive dyes with aggregation-induced enhanced emission characteristics

Alkynylated aroyl-S,N-ketene acetals are readily synthesized in mostly excellent yields by a Sonogashira reaction resulting in a substance library of more than 20 examples. Upon expansion of the reaction sequence by deprotection and concatenating of the copper-click reaction in a one-pot fashion, a library of 11 triazole-ligated aroyl-S,N-ketene acetals is readily accessible. All derivatives show pronounced solid-state emission and aggregation-induced emission properties depending on the nature of the alkynyl or the triazole substituents.

Anti-Oxidation Agents to Prevent Dye Degradation in Organic-Based Host-Guest Systems Suitable for Luminescent Solar Concentrators

Luminescent solar concentrators (LSCs) have been extensively studied as they offer a practical solution to increase the efficiency of silicon-based photovoltaics (PVs). In this context, the use of natural and organic luminescent materials is desirable in order to obtain sustainable and environmentally friendly devices. Moreover, solution-processable organic host-guest systems based on Foerster Resonant Energy Transfer (FRET) processes offer the possibility to exploit a low-cost technique to obtain an efficient energy downshift from the UV-visible to red or deep red emissions in order to concentrate the radiation in the area of maximum efficiency of the PV device. Nevertheless, organic materials are subjected to photodegradation that reduces their optical properties when exposed to UV light and oxygen. In this work, we incorporated two different antioxidant molecules (i.e., octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Octa) and L-ascorbic acid (L-Asc)) in a three-dye host-guest system and studied the corresponding optical properties after prolonged irradiation times in air. It was found that the presence of the antioxidants, especially L-Asc, slowed the system's photodegradation down whilst at the same time retaining high emission efficiencies and without interfering with the cascade Resonant Energy Transfer processes among the dyes inserted in the nanochannels of the host.

Förster Resonance Energy Transfer in Luminescent Solar Concentrators

Luminescent solar concentrators (LSCs) are an emerging technology to collect and channel light from a large absorption area into a smaller one. They are a complementary technology for traditional solar photovoltaics (PV), particularly suitable for application in urban or indoor environments where their custom colors and form factors, and performance under diffuse light conditions may be advantageous. Förster resonance energy transfer (FRET) has emerged as a valuable approach to overcome some of the intrinsic limitations of conventional single lumophore LSCs, such as reabsorption or reduced quantum efficiency. This review outlines the potential of FRET to boost LSC performance, using highlights from the literature to illustrate the key criteria that must be considered when designing an FRET-LSC, including both the photophysical requirements of the FRET lumophores and their interaction with the host material. Based on these criteria, a list of design guidelines intended to aid researchers when they approach the design of a new FRET-LSC system is presented. By highlighting the unanswered questions in this field, the authors aim to demonstrate the potential of FRET-LSCs for both conventional solar-harvesting and emerging LSC-inspired technologies and hope to encourage participation from a diverse researcher base to address this exciting challenge.

AIEE compounds based on 9, 10-dithienylanthracene-substituted triphenylamine: design, synthesis, and applications in cell imaging

Four new 9, 10-dithienylanthracene-based triphenylamine derivatives (TPA-DTAs) were designed and synthesized by adjusting the linkage model of phenylacetonitrile group with different substituents. They all displayed aggregation-induced emission enhancement (AIEE) features...

Application of Triplet-Triplet Annihilation Upconversion in Organic Optoelectronic Devices: Advances and Perspectives

Organic semiconductor materials have been widely used in various optoelectronic devices due to their rich optical and/or electrical properties, which are highly related to their excited states. Therefore, how to manage and utilize the excited states in organic semiconductors is essential for the realization of high-performance optoelectronic devices. Triplet-triplet annihilation (TTA) upconversion is a unique process of converting two non-emissive triplet excitons to one singlet exciton with higher energy. Efficient optical-to-electrical devices can be realized by harvesting sub-bandgap photons through TTA-based upconversion. In electrical-to-optical devices, triplets generated after the combination of electrons and holes also can be efficiently utilized via TTA, which resulted in a high internal conversion efficiency of 62.5%. Currently, many interesting explorations and significant advances have been demonstrated in these fields. In this review, a comprehensive summary of these intriguing advances on developing efficient TTA upconversion materials and their application in optoelectronic devices is systematically given along with some discussions. Finally, the key challenges and perspectives of TTA upconversion systems for further improvement for optoelectronic devices and other related research directions are provided. This review hopes to provide valuable guidelines for future related research and advancement in organic optoelectronics.

Aggregation-induced emission from silole-based lumophores embedded in organic-inorganic hybrid hosts

Aggregation-induced emitters - or AIEgens - are often symbolised by their photoluminescence enhancement as a result of aggregation in a poor solvent. However, for some applications, it is preferable for the AIE response to be induced in the solid-state. Here, the ability of an organic-inorganic hybrid polymer host to induce the AIE response from embedded silole-based lumophores has been explored. We have focussed on understanding how the incorporation method controls the extent of lumophore aggregation and thus the associated photophysical properties. To achieve this, two sample concentration series have been prepared, based on either the parent AIEgen 1,1-dimethyl-2,3,4,5-tetraphenylsilole (DMTPS) or the silylated analogue (DMTPS-Sil), which were physically doped or covalently grafted, respectively, to dU(600) - a member of the ureasil family of poly(oxyalkylene)/siloxane hybrids. Steady-state and time-resolved photoluminescence measurements, coupled with confocal microscopy studies, revealed that covalent grafting leads to improved dispersibility of the AIEgen, reduced scattering losses, increased photoluminescence quantum yields (up to ca. 40%) and improved chemical stability. Moreover, the ureasil also functions as a photoactive host that undergoes excitation energy transfer to the embedded DMTPS-Sil with an efficiency of almost 70%. This study highlights the potential for designing complex photoluminescent hybrid polymers exhibiting an ehanced AIE response for solid-state optical applications.

Molecular Fluorophores Self-Organize into C-Dot Seeds and Incorporate into C-Dot Structures

Various molecular fluorophores have been identified to be present during carbon-dot (C-dot) syntheses. However, the organization of such fluorophores in C-dots is still unknown. We study the self-assembly of 5-oxo-1,2,3,5-tetrahydroimidazo-[1,2-α]-pyridine-7-carboxylic acid (IPCA), a molecular fluorophore present during the synthesis of C-dots from citric acid and ethylenediamine. Both forms of IPCA (neutral and anionic) show a tendency to self-assemble into stacked systems, forming seeds of C-dots during their synthesis. IPCA also interacts with graphitic C-dot building blocks, fragments easily, and incorporates into their structures via π-π stacking. Both IPCA forms are able to create adlayers internally stabilized by an extensive hydrogen bonding network, with an arrangement of layers similar to that in ordinary graphitic C-dots. The results show the tendency of molecular fluorophores to form organized stacked seeds of C-dots and incorporate into C-dot structures. Such noncovalent structures can be further covalently interlinked via the carbonization process during C-dot growth.

Identification of Nonradiative Decay Pathways in Cy3

Photoexcited fluorescent markers are extensively used in spectroscopy, imaging, and analysis of biological systems. The performance of fluorescent markers depends on high levels of emission, which are limited by competing nonradiative decay pathways. Small-molecule fluorescent dyes have been increasingly used as markers due to their high and stable emission. Despite their prevalence, the nonradiative decay pathways of these dyes have not been determined. Here, we investigate these pathways for a widely used indocarbocyanine dye, Cy3, using transient grating spectroscopy. We identify a nonradiative decay pathway via a previously unknown dark state formed within ∼1 ps of photoexcitation. Our experiments, in combination with electronic structure calculations, suggest that the generation of the dark state is mediated by picosecond vibrational mode coupling, likely via a conical intersection. We further identify the vibrational modes, and thus structural elements, responsible for the formation and dynamics of the dark state, providing insight into suppressing nonradiative decay pathways in fluorescent markers such as Cy3.

Synthesis, photophysical and electropolymerization properties of thiophene-substituted 2,3-diphenylbuta-1,3-dienes

Electropolymerizable diphenylbuta-1,3-diene derivatives with AIE or AEE properties were synthesized allowing low bandgap polymers to be obtained through electropolymerization processes.

Luminescent Solar Concentrators Based on Energy Transfer from an Aggregation-Induced Emitter Conjugated Polymer

Luminescent solar concentrators (LSCs) are solar-harvesting devices fabricated from a transparent waveguide that is doped or coated with lumophores. Despite their potential for architectural integration, the optical efficiency of LSCs is often limited by incomplete harvesting of solar radiation and aggregation-caused quenching (ACQ) of lumophores in the solid state. Here, we demonstrate a multilumophore LSC design that circumvents these challenges through a combination of nonradiative Förster resonance energy transfer (FRET) and aggregation-induced emission (AIE). The LSC incorporates a green-emitting poly(tetraphenylethylene), p-O-TPE, as an energy donor and a red-emitting perylene bisimide molecular dye (PDI-Sil) as the energy acceptor, within an organic-inorganic hybrid diureasil waveguide. Steady-state photoluminescence studies demonstrate the diureasil host induced AIE from the p-O-PTE donor polymer, leading to a high photoluminescence quantum yield (PLQY) of ∼45% and a large Stokes shift of ∼150 nm. Covalent grafting of the PDI-Sil acceptor to the siliceous domains of the diureasil waveguide also inhibits nonradiative losses by preventing molecular aggregation. Due to the excellent spectral overlap, FRET was shown to occur from p-O-TPE to PDI-Sil, which increased with acceptor concentration. As a result, the final LSC (4.5 cm × 4.5 cm × 0.3 cm) with an optimized donor-acceptor ratio (1:1 by wt %) exhibited an internal photon efficiency of 20%, demonstrating a viable design for LSCs utilizing an AIE-based FRET approach to improve the solar-harvesting performance.

Tetrabenzo[5.7]fulvalene: a forgotten aggregation induced-emission luminogen

Tetrabenzo[5.7]fulvalene has been proven to be an outstanding aggregation-induced emission fluorophore.

Impact of Stokes Shift on the Performance of Near-Infrared Harvesting Transparent Luminescent Solar Concentrators

Visibly transparent luminescent solar concentrators (TLSC) have the potential to turn existing infrastructures into net-zero-energy buildings. However, the reabsorption loss currently limits the device performance and scalability. This loss is typically defined by the Stokes shift between the absorption and emission spectra of luminophores. In this work, the Stokes shifts (SS) of near-infrared selective-harvesting cyanines are altered by substitution of the central methine carbon with dialkylamines. We demonstrate varying SS with values over 80 nm and ideal infrared-visible absorption cutoffs. The corresponding TLSC with such modification shows a power conversion efficiency (PCE) of 0.4% for a >25 cm² device area with excellent visible transparency >80% and up to 0.6% PCE over smaller areas. However, experiments and simulations show that it is not the Stokes shift that is critical, but the total degree of overlap that depends on the shape of the absorption tails. We show with a series of SS-modulated cyanine dyes that the SS is not necessarily correlated to improvements in performance or scalability. Accordingly, we define a new parameter, the overlap integral, to sensitively correlate reabsorption losses in any LSC. In deriving this parameter, new approaches to improve the scalability and performance are discussed to fully optimize TLSC designs to enhance commercialization efforts.

Purine-Furan and Purine-Thiophene Conjugates

Furyl and thienyl moieties were introduced into a purine structure to elevate its fluorescence properties, while a trityl group was used to increase the amorphous properties of the purine compounds. The title compounds were prepared by a sequence involving a Mitsunobu, a SNAr and a Suzuki–Miyaura reaction and their photophysical properties were studied. Quantum yields in the solution reached up to 88% but only up to 5% in the thin layer.

Controlled Dye Aggregation in Sodium Dodecylsulfate-Stabilized Poly(methylmethacrylate) Nanoparticles as Fluorescent Imaging Probes

Polymer nanoparticles are used extensively in biomedical applications. Poly(methylmethacrylate) (PMMA) nanoparticles obtained via nanoprecipitation were unstable and flocculate or precipitate from solution within a few hours. A simple method to improve the stability of the particles using surfactants at low concentrations was carried out to produce PMMA nanoparticles with long-term stability in water (>6 months). The increased stability was attributed to the incorporation of surfactants inside the polymer particles during nanoprecipitation. The same methodology was also adopted to encapsulate a highly fluorescent hydrophobic perylene tetraester inside the polymer nanoparticles with good stability in water. Because of the presence of the anionic sodium dodecyl sulfate, the particles showed a negative zeta potential of -34.7 mV and an average size of 150 nm. Similarly, the dye-encapsulated polymer nanoparticles showed a zeta potential of -35.1 mV and an average particle size of 180 nm. By varying the concentration of encapsulated dyes inside the polymer nanoparticles, dye aggregation could be controlled, and the fluorescence profiles of the nanoparticles were altered. To understand the uptake and toxicity of the polymer nanoparticles, baby hamster kidney cells were chosen as a model system. The polymer nanoparticles were taken up by the cells within 3 h and were nontoxic at concentrations as high as 100 ppm. The confocal micrographs of the cells revealed localized fluorescence from the polymer nanoparticles around the nucleus in the cytoplasm without the penetration of the nuclear envelope.

Construction of J-type aggregates as multi-functional interlayers for nonfullerene polymer solar cells

Light-absorbing J-aggregates: a new strategy to develop high performance cathode interlayers with solar concentrating functions.

Luminescent solar concentrators based on PMMA films obtained from a red-emitting ATRP initiator

PMMA_TPE_RED polymers containing 0.98–3.05 wt% of a red-emitting AIEgen were prepared and proposed as high performance luminescent solar concentrators.

Fluorescent Sensors Based on Aggregation-Induced Emission: Recent Advances and Perspectives

Fluorescent sensors with advantages of excellent sensitivity, rapid response, and easy operation are emerging as powerful tools in environmental monitoring, biological research, and disease diagnosis. However, conventional fluorophores featured with π-planar structures usually suffer from serious self-quenching in the aggregated state, poor photostability, and small Stokes' shift. In contrast to conventional aggregation-caused quenching (ACQ) fluorophores, the newly emerged aggregation-induced emission fluorogens (AIEgens) are featured with high emission efficiency in the aggregated state, which provide unique opportunities for various sensing applications with advantages of high signal-to-noise ratio, strong photostability, and large Stokes' shift. In this review, we will first briefly give an introduction of the AIE concept and the turn-on sensing principles. Then, we will discuss the recent examples of AIE sensors according to types of analytes. Finally, we will give a perspective on the future developments of AIE sensors. We hope this review will inspire more endeavors to devote to this emerging world.

Ultrawide Spectral Response of CIGS Solar Cells Integrated with Luminescent Down-Shifting Quantum Dots

Conventional Cu(In_1-x,Ga_x)Se₂ (CIGS) solar cells exhibit poor spectral response due to parasitic light absorption in the window and buffer layers at the short wavelength range between 300 and 520 nm. In this study, the CdSe/CdZnS core/shell quantum dots (QDs) acting as a luminescent down-shifting (LDS) layer were inserted between the MgF₂ antireflection coating and the window layer of the CIGS solar cell to improve light harvesting in the short wavelength range. The LDS layer absorbs photons in the short wavelength range and re-emits photons in the 609 nm range, which are transmitted through the window and buffer layer and absorbed in the CIGS layer. The average external quantum efficiency in the parasitic light absorption region (300-520 nm) was enhanced by 51%. The resulting short circuit current density of 34.04 mA/cm² and power conversion efficiency of 14.29% of the CIGS solar cell with the CdSe/CdZnS QDs were improved by 4.35 and 3.85%, respectively, compared with those of the conventional solar cells without QDs.

Towards Efficient Spectral Converters through Materials Design for Luminescent Solar Devices

Single-junction photovoltaic devices exhibit a bottleneck in their efficiency due to incomplete or inefficient harvesting of photons in the low- or high-energy regions of the solar spectrum. Spectral converters can be used to convert solar photons into energies that are more effectively captured by the photovoltaic device through a photoluminescence process. Here, recent advances in the fields of luminescent solar concentration, luminescent downshifting, and upconversion are discussed. The focus is specifically on the role that materials science has to play in overcoming barriers in the optical performance in all spectral converters and on their successful integration with both established (e.g., c-Si, GaAs) and emerging (perovskite, organic, dye-sensitized) cell types. Current challenges and emerging research directions, which need to be addressed for the development of next-generation luminescent solar devices, are also discussed.

Solid-state source of intense yellow light based on a Ce:YAG luminescent concentrator

A luminescent concentrator functioning as a bright source of yellow light is reported. It comprises a waveguide made of cerium-doped YAG crystal, in the form of a long-thin rectangular strip, surrounded by flowing air and optically pumped from both sides with blue light from arrays of high-efficiency InGaN LEDs. Phosphor-converted yellow light, generated within the strip, is guided to a glass taper that is butt-coupled to one of the strip's end faces. Up to 20 W of optical power, centered on 575 nm with a linewidth of 76 nm, can be continuously radiated into air from the taper's 1.67 mm × 1.67 mm square output aperture. The intensity of the outputted light is significantly greater than what any yellow (AlGaInP) LED can directly produce (either singly or arrayed), with only a modest increase in linewidth. Furthermore, the wall-plug efficiency of the source exceeds that of any yellow laser. The concept allows for further substantial increases in intensity, total output power and wall-plug efficiency through scaling-up and engineering refinements.

Applications of Fluorogens with Rotor Structures in Solar Cells

Solar cells are devices that convert light energy into electricity. To drive greater adoption of solar cell technologies, higher cell efficiencies and reductions in manufacturing cost are necessary. Fluorogens containing rotor structures may be helpful in addressing some of these challenges due to their unique twisted structures and photophysics. In this review, we discuss the applications of rotor-containing molecules as dyes for luminescent down-shifting layers and luminescent solar concentrators, where their aggregation-induced emission properties and large Stokes shifts are highly desirable. We also discuss the applications of molecules containing rotors in third-generation solar cell technologies, namely dye-sensitized solar cells and organic photovoltaics, where the twisted 3-dimensional rotor structures are used primarily for aggregation control. Finally, we discuss perspectives on the future role of molecules containing rotor structures in solar cell technologies.

Emissive Molecular Aggregates and Energy Migration in Luminescent Solar Concentrators

Luminescent solar concentrators (LSCs) are light harvesting devices that are ideally suited to light collection in the urban environment where direct sunlight is often not available. LSCs consist of highly luminescent compounds embedded or coated on a transparent substrate that absorb diffuse or direct solar radiation over a large area. The resulting luminescence is trapped in the waveguide by total internal reflection to the thin edges of the substrate where the concentrated light can be used to improve the performance of photovoltaic devices. The concept of LSCs has been around for several decades, and yet the efficiencies of current devices are still below expectations for commercial viability. There are two primary challenges when designing new chromophores for LSC applications. Reabsorption of dye emission by chromophores within the waveguide is a significant loss mechanism attenuating the light output of LSCs. Concentration quenching, particularly in organic dye systems, restricts the quantity of chromophores that can be incorporated in the waveguide thus limiting the light absorbed by the LSC. Frequently, a compromise between increased light harvesting of the incident light and decreasing emission quantum yield is required for most organic chromophore-based systems due to concentration quenching. The low Stokes shift of common organic dyes used in current LSCs also imposes another optimization problem. Increasing light absorption of LSCs based on organic dyes to achieve efficient light harvesting also enhances reabsorption. Ideally, a design strategy to simultaneously optimize light harvesting, concentration quenching, and reabsorption of LSC chromophores is clearly needed to address the significant losses in LSCs. Over the past few years, research in our group has targeted novel dye structures that address these primary challenges. There is a common perception that dye aggregates are to be avoided in LSCs. It became apparent in our studies that aggregates of chromophores exhibiting aggregation-induced emission (AIE) behavior are attractive candidates for LSC applications. Strategic application of AIE chromophores has led to the development of the first organic-based transparent solar concentrator that harvests UV light as well as the demonstration of reabsorption reduction by taking advantage of energy migration processes between chromophores. Further developments led us to the application of perylene diimides using an energy migration/energy transfer approach. To prevent concentration quenching, a molecularly insulated perylene diimide with bulky substituents attached to the imide positions was designed and synthesized. By combining the insulated perylene diimide with a commercial perylene dye as an energy donor-acceptor emitter pair, detrimental luminescence reabsorption was reduced while achieving a high chromophore concentration for efficient light absorption. This Account reviews and reinspects some of our recent work and the improvements in the field of LSCs.

Bigger and Brighter Fluorenes: Facile π-Expansion, Brilliant Emission and Sensing of Nitroaromatics

π-Expanded butterfly-like 2D fluorenes and 3D spirobifluorenes 1-5 were synthesized via a DDQ-mediated oxidative cyclization strategy with a high regioselectivity. Through structural modification via π-expansion, it was possible to achieve near-ultraviolet absorption, bright-blue emission, very high near-unity fluorescence quantum yields in solution as well as in film states, and deep-lying HOMO energy levels with excellent thermal stabilities. Furthermore, these electron-rich compounds displayed a notable behavior towards sensing of nitroaromatic explosives, such as picric acid, up to a detection limit of 0.2 ppb.

The fluorescent bioprobe with aggregation-induced emission features for monitoring to carbon dioxide generation rate in single living cell and early identification of cancer cells

A novel fluorescent probe, tris (2-(dimethylamino) ethyl)-4,4',4″-(1H-pyrrole-1,2,5-triyl) tribenzoate (TPP-TMAE), with aggregation-enhanced emission (AEE) feature showed a simple, highly selective, specific, and instant response to trace amount carbon dioxide (CO2). Because of this special characteristic, TPP-TMAE is ideal to be a biomarker for in-situ monitoring of the CO2 generation rate during the metabolism of single living cell. The rates in single living HeLa cell, MCF-7 cell, and MEF cell were 6.40 × 10(-6)±6.0 × 10(-8) μg/h, 5.78 × 10(-6)±6.0 × 10(-8) μg/h, and 4.27 × 10(-7)±4.0 × 10(-9) μg/h, respectively. The distinct responses of TPP-TMAE to CO2 generated from cancer cells and normal cells suggested TPP-TMAE as a useful tool for deeper understanding metabolism process and distinguishing cancer cells from normal cells during the early diagnosis of cancers.

From ACQ to AIE: the suppression of the strong π–π interaction of naphthalene diimide derivatives through the adjustment of their flexible chains

The adjustment of flexible chains can realize the transformation from ACQ to AIE with the tunable packing modes, providing an alternative approach for the inhibition of unwanted π–π stacking.

Lasing properties of a cholesteric liquid crystal containing aggregation-induced-emission material

We demonstrate band edge lasing action from a cholesteric liquid crystal (CLC) containing an aggregation-induced-emission (AIE) dye as gain material. AIE materials do not suffer aggregation-caused quenching, have strong resistance to photobleaching, and can show large Stokes shift. The amplified spontaneous emission (ASE) and lasing emission of the dye-doped CLC cell have been characterized, the lasing threshold has been estimated, and its resistance to photobleaching has been measured. AIE materials with their unique properties are especially suitable for acting as gain materials in liquid crystal lasers where defect structures lower the threshold for nanoscale aggregation effects. Our studies have shown that such AIE-dye-doped CLC is capable of lasing action with unusually large Stokes shift at moderate threshold with strong resistance to photobleaching.

Aggregation-induced emission and aggregation-promoted photochromism of bis(diphenylmethylene)dihydroacenes

Reported herein is a new class of pure polycyclic hydrocarbon molecules, designed through a novel aggregation-induced emission (AIE) strategy, with unexpected photochromic properties. The restriction of intramolecular motion was found as a comprehensive mechanism for the AIE effect. The photochromism mechanism study revealed that the photocyclization reaction of cis-stilbene, the molecular conformation in the single crystal and the tetracene backbone should contribute to the unique photo behavior. In particular, the fast responsive, photo-reversible and thermo-irreversible photochromic effect facilitated in the solid state opens a new field of aggregation-promoted photochromism.

Efficient light harvesting of a luminescent solar concentrator using excitation energy transfer from an aggregation-induced emitter

The compromise between light absorption and reabsorption losses limits the potential light conversion efficiency of luminescent solar concentrators (LSCs). Current approaches do not fully address both issues. By using the excitation energy transfer (EET) strategy with a donor chromophore that exhibits aggregation-induced emission (AIE) behaviour, it is shown that both transmission and reabsorption losses can be minimized in a LSC device achieving high light collection and concentration efficiencies. The light harvesting performance of the LSC developed has been characterized using fluorescence quantum yield measurements and Monte Carlo ray tracing simulations. Comparative incident photon conversion efficiency and short-circuit current data based on the LSC coupled to a silicon solar cell provide additional evidence for improved performance.