Showing papers by "Jacky Wing Yip Lam published in 2012"

Tetraphenylethene: a versatile AIE building block for the construction of efficient luminescent materials for organic light-emitting diodes

Abstract: Luminescent materials with efficient solid-state emissions are important for the advancement of optoelectronics. Recently, a new class of propeller-like luminogenic molecules with aggregation-induced emission (AIE) characteristics has drawn increasing research interest. Among them, tetraphenylethene (TPE) is an archetypal luminogen with a simple molecule structure but shows a splendid AIE effect. Utilizing TPE as a building block, an effective strategy to create efficient solid-state emitters is developed. In this feature article, we review mainly our recent work on the construction of luminogenic materials from TPE and present their applications in organic light-emitting diodes. The applicability of the synthetic strategy and the utility of the resulting materials are demonstrated.

Efficient Solid Emitters with Aggregation-Induced Emission and Intramolecular Charge Transfer Characteristics: Molecular Design, Synthesis, Photophysical Behaviors, and OLED Application

Abstract: Emissive electron donor–acceptor (D–A) conjugates have a wide variety of applications in biophotonics, two-photon absorption materials, organic lasers, long wavelength emitters, and so forth. However, it is still a challenge to synthesize high solid-state efficiency D–A structured emitters due to the notorious aggregation-caused quenching (ACQ) effect. Though some D–A systems are reported to show aggregation-induced emission (AIE) behaviors, most are only selectively AIE-active in highly polar solvents, showing decreased solid-sate emission efficiencies compared to those in nonpolar solvents. Here we report the triphenylamine (TPA) and 2,3,3-triphenylacrylonitrile (TPAN) based D–A architectures, namely, TPA3TPAN and DTPA4TPAN. Decoration of arylamines with TPAN changes their emission behaviors from ACQ to AIE, making resulting TPA3TPAN and DTPA4TPAN nonluminescent in common solvents but highly emissive when aggregated as nanoparticles, solid powders, and thin films owing to their highly twisted configurat...

Monitoring and Inhibition of Insulin Fibrillation by a Small Organic Fluorogen with Aggregation-Induced Emission Characteristics

Abstract: Amyloid fibrillation of proteins is associated with a great variety of pathologic conditions. Development of new molecules that can monitor amyloidosis kinetics and inhibit fibril formation is of great diagnostic and therapeutic value. In this work, we have developed a biocompatible molecule that functions as an ex situ monitor and an in situ inhibitor for protein fibrillation, using insulin as a model protein. 1,2-Bis[4-(3-sulfonatopropoxyl)phenyl]-1,2-diphenylethene salt (BSPOTPE) is nonemissive when it is dissolved with native insulin in an incubation buffer but starts to fluoresce when it is mixed with preformed insulin fibril, enabling ex situ monitoring of amyloidogenesis kinetics and high-contrast fluorescence imaging of protein fibrils. Premixing BSPOTPE with insulin, on the other hand, inhibits the nucleation process and impedes the protofibril formation. Increasing the dose of BSPOTPE boosts its inhibitory potency. Theoretical modeling using molecular dynamics simulations and docking reveals that BSPOTPE is prone to binding to partially unfolded insulin through hydrophobic interaction of the phenyl rings of BSPOTPE with the exposed hydrophobic residues of insulin. Such binding is assumed to have stabilized the partially unfolded insulin and obstructed the formation of the critical oligomeric species in the protein fibrillogenesis process.

What makes efficient circularly polarised luminescence in the condensed phase: aggregation-induced circular dichroism and light emission

Abstract: In this contribution, we conceptually present a new avenue to construction of molecular functional materials with high performance of circularly polarised luminescence (CPL) in the condensed phase. A molecule (1) containing luminogenic silole and chiral sugar moieties was synthesized and thoroughly characterized. In a solution of 1, no circular dichroism (CD) and fluorescence emission are observed, but upon molecular aggregation, both the CD and fluorescence are simultaneously turned on, showing aggregation-induced CD (AICD) and emission (AIE) effects. The AICD effect is supported by the fact that the molecules readily assemble into right-handed helical nanoribbons and superhelical ropes when aggregated. The AIE effect boosts the fluorescence quantum efficiency (ΦF) by 136 fold (ΦF, ∼0.6% in the solution versus ∼81.3% in the solid state), which surmounts the serious limitations of aggregation-caused quenching effect encountered by conventional luminescent materials. Time-resolved fluorescence study and theoretical calculation from first principles conclude that restriction of the low-frequency intramolecular motions is responsible for the AIE effect. The helical assemblies of 1 prefer to emit right-handed circularly polarised light and display large CPL dissymmetry factors (gem), whose absolute values are in the range of 0.08–0.32 and are two orders of magnitude higher than those of commonly reported organic materials. We demonstrate for the first time the use of a Teflon-based microfluidic technique for fabrication of the fluorescent pattern. This shows the highest gem of −0.32 possibly due to the enhanced assembling order in the confined microchannel environment. The CPL performance was preserved after more than half year storage under ambient conditions, revealing the excellent spectral stability. Computational simulation was performed to interpret how the molecules in the aggregates interact with each other at the molecular level. Our designed molecule represents the desired molecular functional material for generating efficient CPL in the solid state, and the current study shows the best results among the reported organic conjugated molecular systems in terms of emission efficiency, dissymmetry factor, and spectral stability.

Luminogenic materials constructed from tetraphenylethene building blocks: Synthesis, aggregation-induced emission, two-photon absorption, light refraction, and explosive detection

Abstract: Luminogenic molecules [(TPE)3 (1), TPE-C = C-TPE-C = C-TPE (2), and TPE-C≡C-TPE-C≡C-TPE (3)] and their polymers P1–P3 are constructed from tetraphenylethene (TPE) building blocks in high yields by Suzuki, Witting, and Sonogashira coupling reactions. All the compounds are soluble and enjoy high thermal stability, losing little of their weights when they are heated to 290–528 °C under nitrogen or 288–436 °C in air. Analyses by UV spectroscopy and cyclic voltammetry as well as theoretical calculations show that the conjugation of the luminophores is in the order of 2 > 3 > 1, P2 > P3 > P1, and P1–P3 > 1–3. All the molecules and polymers are weakly emissive in solutions. They, however, become strong emitters in the aggregate state with fluorescence quantum yields up to 90%. Both 1–3 and P1–P3 exhibit the feature of aggregation-enhanced two-photon excited fluorescence. Large two-photon absorption cross sections (up to ∼900 GM) are observed in the nanoaggregates of the polymers. Thin solid films of the polymers show high refractive indices (RI = 1.7649 − 1.6873) in a wide wavelength region of 400–1700 nm, high modified Abbe numbers (vD′ up to 3436), and low optical dispersions (D′ down to 2.9 × 10−4). The light emissions of the polymers can be quenched exponentially by picric acid with large quenching constants, suggesting that they can be utilized as efficient chemosensors for explosive detection.

Efficient Light Emitters in the Solid State: Synthesis, Aggregation-Induced Emission, Electroluminescence, and Sensory Properties of Luminogens with Benzene Cores and Multiple Triarylvinyl Peripherals

Abstract: Benzene-cored luminogens with multiple triarylvinyl units are designed and synthesized. These propeller-shaped molecules are nonemissive when dissolved in good solvents, but become highly emissive when aggregated in poor solvents or in the solid state, showing the novel phenomenon of aggregation-induced emission. Restriction of intramolecular motion is identified as the main cause for this effect. Thanks to their high solid-state fluorescence quantum yields (up to unity) and high thermal and morphological stabilities, light-emitting diodes with the luminogens as emitters give sky-blue to greenish-blue light in high luminance and efficiencies of 10800 cd m−2, 5.8 cd A−1, and 2.7%, respectively. The emissions of the nanoaggregates of the luminogens can be quenched exponentially by picric acid, or selectively by Ru3+, with quenching constants up to 105 and ∼2.0 × 105 L mol−1, respectively, making them highly sensitive (and selective) chemosensors for explosives and metal ions.

An AIE-active hemicyanine fluorogen with stimuli-responsive red/blue emission: extending the pH sensing range by “switch + knob” effect

Abstract: In this work, a red-emissive zwitterionic hemicyanine dye, named TPE–Cy, containing tetraphenylethene (TPE) and N-alkylated indolium is designed and synthesized. TPE–Cy inherits the aggregation-induced emission (AIE) feature of TPE and displays a large Stokes shift (>185 nm), overcoming the limitations of the concentration-quenching effect and small Stokes shift (from a few to 20 nm) encountered by conventional cyanine dyes. By taking advantage of the photophysical AIE property and chemical reactivity towards OH−/H+, TPE–Cy is able to sense pH in a broad range (the broadest to date) by showing different emission colors and intensities: strong to moderate red emission at pH 5–7, weak to no emission at pH 7–10, and no emission to strong blue emission at pH 10–14. The acid/base-switched red/blue emission transition is reversible and can be repeated for many cycles. By means of NMR and HRMS analyses, we have drawn a mechanistic picture at molecular level to illustrate how this dye works as a pH-sensitive fluorescent probe.

Deciphering mechanism of aggregation-induced emission (AIE): Is E–Zisomerisation involved in an AIE process?

Abstract: In this work, we address a mechanistic issue on AIE process and correct a long-held misconception on stilbene photoluminescence. E–Zisomerisation has been generally recognized as the cause of emission quenching in stilbene solutions. A natural question arisen from this common belief is whether suppression of E–Zisomerisation by aggregate formation in a stilbenic fluorogen system is responsible for its AIE phenomenon. Monitoring of the structural change of a stilbene derivative named 1,2-diphenyl-1,2-di(p-tolyl)ethene by NMR during UV irradiation reveals that the E–Zisomerisation is not involved in its AIE process under the normal photoluminescence spectral measurement conditions.

High efficiency luminescent liquid crystal: aggregation-induced emission strategy and biaxially oriented mesomorphic structure

Abstract: Rational combination of aggregation-induced emission active luminogens and mesogens generates high solid-state efficiency luminescent liquid crystals, thus resolving the problem of aggregation-caused quenching normally occurs in the fabrication of luminescent mesomorphic films.

Using tetraphenylethene and carbazole to create efficient luminophores with aggregation-induced emission, high thermal stability, and good hole-transporting property

Abstract: Tetraphenylethene (TPE) is an archetypal luminogen that exhibits a phenomenon of aggregation-induced emission (AIE), while carbazole is a conventional chromophore which shows the opposite effect of aggregation-caused quenching (ACQ) of light emission in the condensed phase. Melding the two units at the molecular level generates a group of new luminescent materials that suffer no ACQ effect but depict high solid-state fluorescence quantum yields up to unity, demonstrative of the uniqueness of the approach to solve the ACQ problem of traditional luminophores. All the TPE–carbazole adducts are thermally and morphologically stable, showing high glass-transition temperatures (up to 179 °C) and thermal-degradation temperatures (up to 554 °C). Multilayer electroluminescence devices with configurations of ITO/NPB/emitter/TPBi/Alq3/LiF/Al are constructed, which exhibit sky blue light in high luminance (up to 13 650 cd m−2) and high current and external quantum efficiencies (up to 3.8 cd A−1, and 1.8%, respectively). The devices of the luminogens fabricated in the absence of NPB or hole-transporting layer show even higher efficiencies up to 6.3 cd A−1 and 2.3%, thanks to the good hole-transporting property of the carbazole unit.

A tetraphenylethene-based red luminophor for an efficient non-doped electroluminescence device and cellular imaging

Abstract: An efficient red luminophor (TTPEBTTD) consisting of a 4,7-di(thiophen-2-yl)benzo-2,1,3-thiadiazole core and tetraphenylethene peripheries is developed. The non-doped electroluminescence device based on TTPEBTTD radiates red light with high efficiency up to 3.7%. The nanoparticles of TTPEBTTD are promising fluorescent visualizers for cellular imaging with low cytotoxicity.

Graphene Oxide as a Novel Nanoplatform for Enhancement of Aggregation-Induced Emission of Silole Fluorophores

Abstract: Graphene, a single-atom-thick carbon sheet with two-dimensional structure, is now under intense investigation because of its intriguing physical properties. [ 1 ] Graphene oxide (GO), one of the most common derivatives of graphene, is also an atomically thin sheet decorated with epoxy and hydroxyl groups in its basal planes and carboxyl groups at its periphery, allowing it to be well dispersed and facilely modifi ed in solution. [ 2 ] Owing to its unique structure, GO, a new type of solution-processable nonstoichiometric material, or its reduced state, that is, reduced graphene oxide (rGO), can complex with various organic, inorganic, and biological molecules, leading to a wide range of potential applications in electronic devices, [ 3 ] solar cells, [ 4 ] biosensors, [ 5 ] etc. It has been widely recognized that GO is an effi cient fl uorescence quencher of many optical substances, including smallmolecule dyes and conjugated polymers, owing to the strong π − π interaction between them, which induces energy transfer or non-radiative dipole–dipole coupling channels. [ 6 ] This unique property has become another promising feature of GO, and has been applied in many GO-based ultrasensitive optical sensors for detection of many biomolecules. [ 7 ] Further exploration of the interplay between this electronically active platform and optoelectronic organic systems is therefore of great signifi cance for its device and sensing applications. Molecular aggregation induced by π − π stacking or hydrophobic interactions is generally known to reduce the

Synthesis and self-assembly of tetraphenylethene and biphenyl based AIE-active triazoles

Abstract: Self-assembly of fluorescent functional materials has attracted increasing interest in the fabrication of optoelectronic and biological nanodevices. Tetraphenylethene (TPE) is a typical dye molecule with aggregation-induced-emission (AIE) characteristics. Melding TPE carrying triple-bond functionality with diazide-containing biphenyl through “click” chemistry generates AIE-active luminogens [1,1′-biphenyl]-4,4′-diyl bis(6-(4-(4-(1,2,2-triphenylvinyl)phenyl)-1H-1,2,3-triazol-1-yl) hexanoate) [1(5)] and [1,1′-biphenyl]-4,4′-diyl bis(11-(4-(4-(1,2,2-triphenylvinyl)phenyl)-1H-1,2,3-triazol-1-yl) undecanoate) [1(10)] with solid state efficiencies up to unity. Slow addition of dilute THF solutions of 1(m) (m = 5, 10) into nonsolvents such as n-hexane and water yields self-assembled white wooly solids. TEM and SEM observations reveal the (helical) nanofibrous structure of the aggregates. Upon cooling from their concentrated hot solutions, 1(m) readily precipitate. Meanwhile, they can also form gels at high concentrations. Both precipitates and gels of 1(m) exhibit structures similar to those of the aggregates formed in nonsolvents. These results indicate that 1(m) can facilely self-assemble into high emission efficiency (helical) nanofibers, thus paving the way for their optoelectronic and biological applications.

Conjugated Hyperbranched Poly(aryleneethynylene)s: Synthesis, Photophysical Properties, Superquenching by Explosive, Photopatternability, and Tunable High Refractive Indices

Abstract: Triphenylamine (TPA)-based conjugated hyperbranched poly(aryleneethynylene)s (PAEs), hb-P1/2, hb-P1/3, and hb-P1/4, were synthesized with high molecular weights and good solubilities through Sonogashira coupling reactions. These PAEs exhibited outstanding thermal stabilities and different emission behaviors. Tetraphenylethene (TPE)-containing hb-P1/2 fluoresced faintly in THF, although its light emission was enhanced by aggregate formation in aqueous media or in thin films, thereby exhibiting an aggregation-induced emission-enhancement (AIEE) effect. Whereas 1,1,2,3,4,5-hexaphenylsilole (HPS)-bearing hb-P1/3 showed no significant change in emission intensity with increasing water content in aqueous media, hb-P1/4, which consisted of TPA-fluorenone donor-acceptor groups, presented almost identical absorptions, but both positive and negative solvatochromic emissions in various solvents. A superquenching effect was observed in the picric-acid-detection process by using nanosuspensions of hb-P1/2. All of the polymers possessed good film formability. UV irradiation of the thin films induced simultaneous photobleaching and cross-linking, thus making them applicable in the fabrication of 2D and 3D patterns. Furthermore, the polymer films also showed high refractive indices, which were tunable upon exposure to UV light.

Systemic Studies of Tetraphenylethene–Triphenylamine Oligomers and a Polymer: Achieving Both Efficient Solid-State Emissions and Hole-Transporting Capability

Abstract: By employing a new synthetic strategy, a series of oligomers and a polymer composed of different number of tetraphenylethene and triphenylamine units was designed and synthesised. The optical physics properties and electroluminescence behaviours were studied comparatively. All the molecules demonstrate an aggregation-induced emission (AIE) phenomenon and bear very high quantum yields in the solid state. The emission wavelengths and quantum efficiencies alternate with the change of the molecular configurations and achieve their maximum at the largest oligomer. The thermal stabilities also become higher along with the increase in the molecular weight. The molecules have suitable HOMO levels that match the work function of the indium tin oxide (ITO) anode. They can act as both light-emitting and hole-transporting materials in OLEDs. Thus the present strategy combines the intrinsic emissive nature of AIE materials and the good hole-transport capability of aromatic amines, thereby achieving a win-win for both optical and electrical properties.

Efficient Polymerization of Azide and Active Internal Alkynes

Abstract: The 1,3-dipolar cycloaddition of azides and active internal alkynes has been well studied, but is rarely utilized as a tool for polymer preparation. In this work, an efficient polymerization route is developed. Polycycloaddition of diazide (4) and bis(benzoylethynyl)-benzenes and -butane (3) at elevated temperature has produced the first examples of soluble 1,4,5-trisubstituted polytriazoles PI with satisfactory molecular weights (M(w) up to 16 400) in excellent yields (up to 98.6%). All the obtained polymers are thermally stable, losing merely 5% of their weights at temperatures higher than 367 °C. They exhibit higher refractive indices than some commercial plastics and can be crosslinked upon UV irradiation to generate a 3D photopattern with high resolution. The metal-free feature of such a methodology offers a facile tool to prepare functional materials free from the contamination of metal species.

Silole‐containing poly(silylenevinylene)s: Synthesis, characterization, aggregation‐enhanced emission, and explosive detection

Abstract: Hydrosilylation polymerizations of 1,1-dimethyl-2,5-bis(4-ethynylphenyl)-3,4-diphenylsilole with aromatic silylhydrides including 1,4-bis(dimethylsilyl)benzene, 4,4′-bis(dimethylsilyl)biphenyl, 2,5-bis(dimethylsilyl)thiophene, and 2,7-bis(dimethylsilyl)-9,9-dihexylfluorene in the presence of Rh(PPh3)3Cl catalyst in refluxed tetrahydrofuran afford a series of silole-containing poly(silylenevinylene)s. Under optimum condition, the alkyne polyhydrosilylation reactions progress efficiently and regioselectively, yielding polymers with high molecular weights (Mw up to 95,300) and good stereoregularity (E content close to 99%) in high yields (up to 92%). The polymers are processable and thermally stable, with high decomposition temperatures in the range of 420−449 °C corresponding to 5% weight loss. They are weakly fluorescent in the solution state but become emissive in the aggregate and film states, demonstrating their aggregation-enhanced emission characteristics. The explosive sensing capabilities of the polymers are examined in both solution and aggregate states. The emissions of the polymers aggregates in aqueous mixture are quenched more efficiently by picric acid in an exponential pattern with high quenching constants (up to 27,949 L mol−1), suggesting that the polymers aggregates are sensitive chemosensors for explosive detection. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Tuning the electronic nature of aggregation-induced emission chromophores with enhanced electron-transporting properties

Abstract: In organic light-emitting devices, materials with efficient electron-transporting properties, are essential. In this report, oxadiazole-containing tetraphenylethene TPE-Oxa is synthesized and its optical physics and electronic properties are investigated. The dye is almost nonluminescent when molecularly dissolved in solutions, but becomes highly emissive when aggregated in poor solvents or fabricated as thin films in the solid state. A quantum yield of unity has been achieved in its solid thin film. Inherited from the oxadiazole component, the dye molecule enjoys low-lying electronic band energies. Benefiting from the good electron-transporting and hole-blocking properties of the dye, the two-layer OLED devices using TPE-Oxa as both light-emitting and electron-transporting materials show superior performance, i.e., lower turn-on voltage, higher brightness and efficiencies, to the devices of typical configuration with a dedicated electron-transporting layer.

Tunable Helical Assemblies of l-Alanine Methyl Ester-Containing Polyphenylacetylene

Abstract: The self-assemblying behaviors of l-alanine methyl ester-containing polyphenylacetylene (PPA-Ala, in Chart 1) were investigated upon the evaporation of its solvent on mica and on air/water interfaces. The introduction of chiral amino acid attachments to the polyphenylacetylene backbone induced a helical conformation of the backbone, which was stabilized by various noncovalent interactions, especially hydrophobic effect and hydrogen bonds. The helicity of the polymer was further amplified in its higher-order self-assemblies as the formation of helical fibers on the surface of mica upon natural evaporation of its THF solution. By LB technique, the polymer chains were guided to form ordered parallel ridges and highly aligned, with their helical conformation still remaining. The reorganization of the chiral polymer chains on air/water interface was associated with the additional hydrophobic effect of PPA-Ala on an air/water interface. The polymer backbones had to adopt different arrangements to minimize their...

A fully substituted 3-silolene functions as promising building block for hyperbranched poly(silylenevinylene).

Abstract: A 3-silolene derivative, 2,2,5,5-tetrakis(dimethylsilyl)-1,1-dimethyl-3,4-diphenyl-3-silolene (TDMSHS), is first synthesized and characterized by X-ray diffraction crystallography and spectroscopic methods. Hydrosilylation polymerization of TDMSHS with 1,1-dimethyl-2,5-bis(4-ethynylphenyl)-3,4-diphenylsilole in the presence of Karstedt's catalyst generates a stereoregular silole-containing hyperbranched poly(silylenevinylene) (hb-SPSV) with a high molecular weight (M(w) = 146,000, M(w)/M(n) = 1.5) in high yield (≈95%). hb-SPSV exhibits excellent thermal stability and strong fluorescence, and the emission of its aggregates in aqueous mixture can be quenched efficiently by picric acid with large quenching constants K(SV) up to 414400 M(-1).

Naphthalene-substituted 2,3,4,5-tetraphenylsiloles: synthesis, structure, aggregation-induced emission and efficient electroluminescence

Abstract: Two thermally stable naphthalene-substituted 2,3,4,5-tetraphenylsiloles, 1,1-dimethyl-2,5-bis[4-(naphthalen-1-yl)phenyl]-3,4-diphenylsilole (D-1-NpTPS) and 1,1-dimethyl-2,5-bis[4-(naphthalen-2-yl)phenyl]-3,4-diphenylsilole (D-2-NpTPS), have been synthesized and fully characterized. D-2-NpTPS shows redder absorption and emission than D-1-NpTPS due to the better conjugation between naphthalen-2-yl groups and phenyl rings at the 2,5-positions of the silole core. While they are weakly fluorescent in solutions, strong luminescence is induced when aggregated in poor solvents or fabricated into solid films, with high fluorescence quantum yields up to 99%, demonstrating their aggregation-induced emission (AIE) feature. Efficient non-doped organic light-emitting diodes utilizing D-1-NpTPS and D-2-NpTPS as light-emitting layers are fabricated. Remarkably high electroluminescence efficiencies of 10.5 cd A−1, 7.3 lm W−1, and 3.2% are acheived by the D-2-NpTPS device.

A Facile Approach to Highly Efficient and Thermally Stable Solid‐State Emitters: Knitting up AIE‐Active TPE Luminogens by Aryl Linkers

Abstract: A facile approach to thermally stable and efficient solid-state emitters is proposed By hooking up tetraphenylethene (TPE) units through aryl linkers under Suzuki coupling conditions, a series of arylene bis(tetraphenylethene)s (TPE-Ar-TPE Ar=2,5-dimethyl-1,4-phenylene, 2,5-bis(hexyloxyl)-1,4-phenylene, 1,5-naphthylene, and 9,10-anthracenylene) are prepared in satisfactory to high yields (67–96 %) These molecules are nonluminescent when dissolved in solutions but become highly emissive when aggregated in poor solvents or fabricated as thin film in the solid state, displaying a phenomenon of aggregation-induced emission Fluorescence quantum yields of 100 % were achieved in the amorphous films of the luminogens The luminogens exhibit mechano-, vapo-, and thermochromism: their emissions can be repeatedly switched between blue and blue-green colors by simple grinding-fuming and grinding-heating cycles owing to the morphological change from a crystalline to an amorphous state and vice versa These compounds are thermally stable, losing little of their weight at high temperatures of 421–452 °C All the luminogens are morphological stable with high glass transition temperatures Multilayer light-emitting diodes with a device configuration of ITO/NPB/dye/TPBi/Alq3/LiF/Al are fabricated, which emit sky-blue electroluminescence with maximum luminance and external quantum efficiency of 7900 cd m−2 and 21 %, respectively

From a fluorescent chromophore in solution to an efficient emitter in the solid state.

Abstract: Polycyclic aromatic hydrocarbons (PAHs) normally exhibit efficient fluorescence in dilute solutions, whereas their emission is significantly quenched in the aggregated state due to the formation of π-aggregates/excimers. The rigid and planar structure of PAHs plays a positive role in terms of fluorescence in solution but a negative one in the aggregated state. To bestow PAHs a luminescent ability in the solid state, we constructed a non-coplanar PAH-substituted ethene. By using the planar PAH fluoranthene as a building block, a highly efficient solid-state emitter with a fluorescence quantum efficiency of unity in the aggregated state was obtained. OLEDs with contain the molecule as an emitter reach a luminance up to 20 520 cd m(-2) and an efficiency of 10 cd A(-1).