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This study provides a reliable strategy to tune the mechanoluminescent colors by adjusting the weak intermolecular interactions., A new mechanoluminescent material (4-(diphenylamino)phenyl)(4-(diphenylphosphanyl)phenyl)methanone (CDpP), which displays tunable mechanoluminescent emission colors, has been designed and successfully synthesized. CDpP shows two distinct mechanoluminescent colors (blue and green) in different crystalline states. Single-crystal analyses and femtosecond transient emission studies reveal that the striking tunable mechanoluminescence properties of CDpP mainly originate from the different C–H···π interactions in the crystal structures. CDpP crystals with more C–H···π interactions show blue mechanoluminescence (ML), and the emission is attributed to the locally excited (LE)-state because the twisting process for the excited state is restricted by C–H···π interactions. Conversely, CDpP crystals with fewer C–H···π interactions display green ML, in which the red-shifted emission band originates from the twisted intramolecular charge transfer (TICT) excited state because the diphenylamine moiety is relatively free to rotate. The manipulation of weak intermolecular interactions in the crystalline state is a useful and reliable strategy for the tuning of the ML emission wavelengths.

Since the realization in 2011 that most aggregation-induced emission (AIE) molecules exhibit mechano-responsive luminescence (MRL), research regarding the MRL of AIE molecules has drawn much attention, and this area has been expanding tremendously. As one of the most extensively studied AIE cores, tetraphenylethylene (TPE) has been widely used to construct MRL molecules. This review will focus on recent advances in MRL of TPE derivatives with AIE properties, including a brief history of mechano-responsive AIE-active materials, mechanistic studies on MRL, mechano-responsive luminogens based on TPE, mechano-responsive luminogens containing multiple AIE-active units, mechano-memory chromism and mechanoluminescence of TPE derivatives. Moreover, this review will give a perspective on the possible opportunities and future challenges that exist in this research area.

A carbazole containing triphenylethylene derivative (TrPEBCar) has been designed and synthesized, which combines aggregation-induced emission (AIE), piezochromism and photochromism together. In the crystalline state, an intensive emission band at 448 nm was detected. After pressing the crystalline solid, a [crystalline–amorphous] morphological transition takes place, in which the resulting amorphous state of TrPEBCar exhibits a different color and a red-shifted emission band at 470 nm. Photochromic behavior of TrPEBCar is achieved by utilizing a stilbene-type intramolecular photocyclization in the crystalline state. In addition, we report for the first time morphology-dependent photochromism, in which the photochromic properties of TrPEBCar are only observed in the crystalline state but not in the amorphous state. Therefore, the methods of pressing/fuming and heating/fuming act as gates to switch the photochromic properties by changing the aggregation states between the crystalline and amorphous states. By combining the piezochromic properties with the photochromic properties, the ON/OFF states of TrPEBCar can easily be observed by the different colors and emission properties. The triphenylethylene derivative with simple molecular structure provides a new approach for gated photochromic materials with both switch and indicator.

Small energy gap boosts dual-channel triplet harvesting via TADF and UOP, which suppresses long-lived triplet concentration quenching. An infrared laser (808 nm) is able to induce persistent emission under ambient conditions., Due to inefficient molecular design strategies, two-photon-excited ultralong organic room temperature phosphorescence (TPUOP) has not yet been reported in single-component materials. Herein, we present an innovative design method by dual-channel triplet harvesting to obtain the first bright TPUOP molecule with a lifetime of 0.84 s and a quantum efficiency of 16.6%. In compound o-Cz the donor and acceptor units are connected at the ortho position of benzophenone, showing intramolecular space charge transfer. Therefore, the two-photon absorption ability is improved due to the enhanced charge transfer character. Moreover, the small energy gap boosts dual-channel triplet harvesting via ultralong thermally activated delayed fluorescence and H-aggregation phosphorescence, which suppresses the long-lived triplet concentration quenching. Through two-photon absorption, a near-infrared laser (808 nm) is able to trigger the obvious ultralong emission under ambient conditions. This research work provides valuable guidance for designing near-infrared-excited ultralong organic room temperature phosphorescence materials.

An ortho-substituent design strategy promoting steric hindrance has afforded excellent AIE-TADF emitters, and high-efficiency TADF-OLEDs have been subsequently demonstrated., Thermally activated delayed fluorescence (TADF) materials have opened a new chapter for high-efficiency and low-cost organic light-emitting diodes (OLEDs). Herein, we describe a novel and effective design strategy for TADF emitters which includes introducing a carbazole donor unit at the ortho-position, at which the donor and acceptor groups are spatially in close proximity to guarantee the existence of intramolecular electrostatic attraction and through-space charge transfer, leading to reduced structural vibrations, suppressed non-radiative decay and rapid radiative decay to avoid excited state energy loss. As a result, a green TADF emitter (2Cz-DPS) showing high solid-state photoluminescence quantum efficiency (91.9%) and excellent OLED performance was produced. Theoretical simulations reveal that the non-adiabatic coupling accelerates the reverse intersystem crossing of 2Cz-DPS, resulting in a state-of-the-art non-doped OLED with an extremely high external quantum efficiency of 28.7%.

We have synthesized a series of fluorene-based fluorophores, in which a central fluorene core has been modified with different peripheral arylene vinylene substituents that are able to activate aggregation-induced emission (AIE) characteristics. 9,9-Dioctylfluorene doubly end-capped at the 2,7-positions with triphenylethene groups, such as 4-(2,2-diphenylvinyl)phenyl (F1-(2,2)-HTPE) and 4-(1,2-diphenylvinyl)phenyl (F1-(1,2)-HTPE) were synthesized and compared to the tetraphenylethene analogue (F1-TPE). Both F1-(2,2)-HTPE and F1-(1,2)-HTPE glow with a deep blue fluorescence in THF solution with emission maxima (λem) of 426 and 403 nm, respectively. The λem slightly red-shifts in the solid-state to 458 nm for F1-(2,2)-HTPE and 437 nm for F1-(1,2)-HTPE. The fluorescence quantum yields (oF) of F1-(2,2)-HTPE (oF=35.1 %) and F1-(1,2)-HTPE (oF=26.2%) were found to be higher in solution compared to the near quenching of F1-TPE (oF=0.1%). Consequently, this results in weaker AIE-stability of F1-(2,2)-HTPE (αAIE=1.5) and F1-(1,2)-HTPE (αAIE=1.9) compared to F1-TPE (αAIE=125), suggesting that four phenyl groups are necessary for efficient AIE-activity of these fluorene bridged arylene vinylene type materials. In addition, decreasing the steric hindrance around the arylene vinylene moiety by removal of a phenyl ring is another method to decrease the AIE characteristics, in a similar manner to the commonly known "phenyl-locking". Non-polar triphenylethenes are poorer AIE materials than their tetraphenylethene analogues. Replacing the hydrogen atom of F1-(2,2)-HTPE with a cyano group affords fluorene end-capped with 2,3,3-triphenylacrylonitrile (F1-TPAN), which boosts the AIE-effect to αAIE=90.5 and red-shifts the solid-state emission (λem=528 nm) with near quenching in THF solution (oF=0.12%). X-ray crystallographic analysis of F1-TPAN indicates that the introduction of cyano groups can not only diminish the intramolecular steric hindrance in comparison of F1-TPE, but also improve the molecular cohesion ability via multiple CH···N interactions.

In this report, we integrated a photoswitchable quencher, a highly emissive yet pH sensitive fluorophore, and a water-soluble polymer with controlled hydrophilicity into a functional nanosystem. The photoswitching quencher is based on dithienylethene (DTE) unit, while the pH-sensitive emitter is naphthalimide (NI) unit and the water-soluble polymer is obtained from polymerization of N-isopropylacrylamide (NIPAM). Together, these three units create a novel super-resolution lysosome highlighter, although individually none can function as a lysotracker. Because the emitter is sensitive to pH, the resulting polymer becomes highly fluorescent in acidic lysosomes. In addition, photoswitching regulates the fluorescence on and off and thus enables super-resolution localization of fluorescent polymers with sub-40 nm spatial resolution in imaging subcellular organelles. Thus, the concept presented here, including the photoswitchable DTE-pH-sensitive NI dyad, is promising to guide the development of future-generatio...

We report on the reversible fluorescence switching of biodegradable nanoparticles of spiropyran-terminated poly(e-caprolactone) (SP-PCL) for super-resolution fluorescence imaging. SP-PCL was synthesized via ring-opening polymerization using hydroxyl-containing SP derivative as the initiator. SP-PCL solution in THF or dioxane exhibits fast photochromism from colorless to blue upon UV irradiation due to the transformation of SPs in SP-PCL into merocyanines (MCs). Although both SP-PCL solution and MC-PCL solution do not fluoresce, SP-PCL nanoparticle dispersion fabricated via nanoprecipitation in aqueous media, in which SP molecules were embedded into the hydrophobic PCL matrix, displays considerable green emission at 530 nm at an excitation wavelength of 420 nm. Upon

In this paper, the bromination of carbazole has been controlled and then subsequent mono, di, tri and tetra-bromocarbazoles have been subjected to Suzuki cross-coupling to yield a series of carbazole-tetraphenylethene (TPE) materials with varying numbers of peripheral TPE groups. Accompanied by 2,7-dibromo-carbazole, five new Cz-TPE materials are successfully synthesized. All the Cz-TPEs are non-fluorescent in THF and emit strong blue-green fluorescence in aggregate states (fw = 90%) and thin films because of their aggregation induced emission (AIE) nature. In THF (10−5 M) solution, all the Cz-TPEs emit deep blue fluorescence after UV irradiation and we find that the more the TPE groups, the slower the enhancement of fluorescence. In thin films (40 nm), the emission maximum blue shift decreases and finally becomes non-emissive after about 1.5 h of UV irradiation for all the Cz-TPEs. We suppose these optical properties are attributed to photo-induced irreversible changes of TPE to diphenylphenanthrene derivatives. The photo-oxidation process for Cz-1TPE has been investigated and proved by HPLC analysis, 1H NMR and LS-MS. Electrochemical properties of all the Cz-TPEs are investigated by cyclic voltammetry and with UV-absorption spectra, and their energy levels are calculated. Finally, we applied the Cz-TPEs to organic light emitting diode (OLED) devices by the spin coating deposition process with OLED devices configuration: ITO/PEDOT (40 nm)/Cz-TPEs (50 nm)/TPBi (40 nm)/LiF (1 nm)/Al (100 nm). All EL devices emit blue-green light with a maximum luminance (Lmax) of 2858, 1353, 986, 2088 and 1129 cd m−2, a maximum current efficiency (ηc,max) of 3.5, 4.9, 3.1, 3.1 and 5.5 cd A−1, a maximum power efficiency (ηP,max) of 2.1, 3.9, 2.2, 1.8 and 3.1 lm W−1 and a turn on voltage (Von) of 3.5, 3.5, 3.3, 3.6 and 4.2 V for Cz-1TPE, Cz-2TPE, Cz-3TPE, Cz-4TPE, Cz-2TPE (2,7), respectively.

The hole-transporting material 4,4′,4″-tri(N-carbazolyl)triphenylamine (TCTA) is widely used as a host in phosphorescent organic light-emitting diodes (PhOLEDs). Based on the unipolar TCTA, we synthesized a novel bipolar host material, (9-(4-(bis(4-(9H-carbazol-9-yl)phenyl)amino)phenyl)-9H-carbazol-3-yl) diphenylphosphine oxide (TCTAPO) by directly imparting an electron-transporting diphenylphosphine oxide moiety to TCTA. It was found that TCTAPO can be used as an ideal versatile host for blue, orange, and white PhOLEDs due to its high triplet energy (ET = 2.83 eV), high glass transition temperature (Tg = 165 °C), and bipolar charge-transporting ability. The maximum power efficiencies of 40.7 and 43.7 lm/W were achieved in the blue and orange PhOLEDs with FIrpic and (fbi)2Ir(acac) as the blue and orange dopants, respectively. Furthermore, the single-emitting-layer white organic light-emitting diode (WOLED) based on the emitter of TCTAPO:FIrpic:(fbi)2Ir(acac) exhibited a maximum current efficiency of 43.7 ...

Four-arm star-shaped PCL polymers are synthesized using iPT as initiator for the controlled ROP of CL at 25–40 °C. The number-average molecular weights of the star-shaped Ti(O-PCL)4 with narrow molecular weight distributions are proportional to the molar ratios of monomer to initiator. The four-branch star-shaped structures of Ti(OPCL)4 are confirmed through polymer hydrolysis monitoring by GPC, which indicates that the stability of the Ti—O bond in the core of the star-shaped polymer chain increases with the increase of polymer molecular weights. The star-shaped Ti(O-PCL)4 can act as a macroinitiator for successive block copolymerization with d,l-Lactide in bulk at 60 °C.

Photosensitive fluorescent probes have become powerful tools in chemical biology and molecular biophysics, which are used to investigate cellular processes with high temporal and spatial resolution. Accordingly, photosensitive fluorescent probes, including photoactivatable, photoconvertible, and photoswitchable fluorophores, have been extensively developed during the past decade. The photoswitchable fluorophores have received much attention because they highlight cellular events clearly. This minireview summarizes recent advances of using reversibly photoswitchable fluorophores and their applications in innovative bioimaging. Photoswitchable fluorophores include photoswitchable fluorescent proteins, photoswitchable fluorescent organic molecules (dyes), and photoswitchable fluorescent nanoparticles. Several strategies have been developed to synthesize photoswitchable fluorophores, including engineering combination proteins, chemical synthesis, polymerization, and self-assembly. Here we concentrate on polymer nanoparticles with optically switchable emission properties: either fluorescence on/off or dual-alternating-color fluorescence photoswitching. The essential mechanisms of fluorescence photoswitching enable different types of photoswitchable fluorophores to change emission intensity or wavelength (color) and thus validating the basis of the fluorescence on/off or dual-color photoswitching design. Generally the possible applications of any fluorophores are to label biological targets, followed by specific imaging. The newly developed photoswitchable fluorophores enable super-resolution fluorescence imaging because of their photosensitive emission. Finally, we summarize the important area regarding future research and development on photoswitchable fluorescent nanoparticles.

Photochromic 1,2-dithienylethene (DTE) derivatives with a high thermal stability and fatigue resistance are appealing for optical switching of fluorescence. Here, we introduce a donor-photochromic bridge-acceptor tetraphenylethene-dithienylethene-perylenemonoimide (TPE-DTE-PMI) triad, in which TPE acts as the electron donor, PMI as the electron acceptor, and DTE as the photochromic bridge. In this system, the localized and intramolecular charge transfer emission of TPE-DTE-PMI with various Stokes shifts have been observed due to the photoinduced intramolecular charge transfer in different solvents. Upon UV irradiation, the fluorescence quenching resulting from photochromic fluorescence resonance energy transfer in TPE-DTE-PMI has been demonstrated in solution and in solid films. The fluorescence on/off switching ratio in polymethylacrylate film exceeds 100, a value much higher than in polymethylmethacrylate film, thus indicating that the fluorescence switching is dependent on matrices.

We study the spectroscopic properties of luminescent liquid crystals which show a glassy nematic phase at room temperature and then form polymer networks by polymerization using ultraviolet light. The reactive mesogens possess fluorene-based aromatic cores with either diene or acrylate photoreactive groups at the end of aliphatic spacers. The photoluminescence quantum efficiency is enhanced when a rigid polymer backbone is formed by crosslinking of the diene endgroups. Spectral shifts of the vibronic transitions confirm an increase in the viscosity of the matrix following photopolymerization. Continuous and time-resolved photoluminescence measurements show that the quantum efficiency is limited by exciton diffusion to traps. Either the diffusion constant or the density of traps is reduced by photopolymerization.

We report the optical properties of tetraphenylethene (TPE) and other TPE derivatives functionalised with an octyl group (TPE-OCT) and polyethyleneglycol group (TPE-PEG) in the side chain. We compared TPE-OCT and TPE-PEG with TPE in both organic solvents and under aqueous conditions. All materials exhibit aggregation-induced emission, however, uncommonly, TPE-PEG seems to aggregate in aqueous solution with enhanced photoluminescence quantum efficiency (PLQE) relative to that in organic solvents. All three materials can be photo-oxidised in solution to their diphenylphenanthrene derivative by irradiation with UV light (at both ≈1 and ≈5 mW cm(-2)), with a subsequent enhancement in PL efficiency. The electron-donating ether group increases the rate of oxidation relative to bare TPE and also photo-oxidation was shown to be solvent and concentration dependent. Finally, photo-oxidation was also demonstrated in the aggregate state.

Starting from MPEG-NH2, a series of amphiphilic triblock copolymers MPEG-b-PLL-b-PLA were synthesized through PEG-NH2-initiated ring-open polymerization of N e-benzyloxycarbonyl-L-lysine, followed by acylation coupling between the amino-terminated MPEG-b-PZLL-NH2 and carboxyl-terminal PLA and the deprotection of amines. The block copolymers were characterized by FT-IR, 1H NMR, GPC, DSC and TEM. The copolymer functional groups, molecular and block structures were verified by FT-IR, 1H NMR and DSC, respectively. The GPC results indicate that the chain lengths of each block can be controlled by varying the feed ratios of the monomer and initiator, providing the polymer samples with a narrow molecular weight distribution (M w /M n = 1.10 ~ 1.25). The TEM analysis shows that the triblock polymers can self-assemble into polymeric micelles in aqueous solution with spherical morphology. The cell-cytotoxicity assay indicates that the triblock polymers show no obvious cytotoxicity against Bel7402 human hepatoma cells.

Light-emitting reactive mesogens are promising materials for photolithographically processable organic light-emitting diodes (OLEDs). We study the photopolymerization of a fluorene-based mesogen with methacrylate photoreactive groups. We find that there is no significant change in the photoluminescence quantum efficiency when the mesogen is photopolymerized in a glovebox with oxygen and water concentration at < 20 parts per million. There is significant quenching of luminescence when the photopolymerization is carried out in a less controlled environment. A real-time measurement is used to monitor changes in the FTIR spectrum of the compound during polymerization. No photoinitiator is added to the mesogen suggesting that the photopolymerization is self-initiated by the chromophore. We show that the self-initiation does not proceed by fragmentation of the aromatic core and suggest an alternative mechanism.

Four different perylene-based electron-acceptors having similar electron affinities, but different thermotropic phases are blended with nematic liquid crystalline electron-donors with a fluorene-thiophene structure to form single layer photovoltaic devices. Best results are obtained when the nematic donor is mixed with an amorphous acceptor to give a supercooled nematic glass at room temperature. Atomic force microscopy operating in the phase contrast mode reveals phase separation on a nanometer scale with a broad distribution of domain sizes peaking at 26 nm. We correlate the morphology of the different blends with the performance of the photovoltaic devices. Power conversion efficiencies up to 0.9 % are obtained with excitation at 470 nm.

Novel heterocyclic and photopolymerizable liquid crystalline materials (reactive mesogens) with smectic phases have been synthesized and characterized. A selection of heterocyclic rings, such as benzothiazole, benzothiadiazole and pyrimidine, has been incorporated into the aromatic core to control the electrochemical/luminescence properties and the structural geometry. Particular emphasis is focused on structure–property relationships, in which the variation of molecular structure and its subsequent effect on the liquid crystalline transition temperatures have been investigated.

We describe the synthesis and characterisation of a novel hole transporting photoalignment copolymer for linearly polarised emission. The copolymer has a coumarin side-chain which undergoes (2 + 2) cycloaddition on irradiation with ultraviolet light. A fluorene side-chain, whose ionisation potential is well matched to the work-function of indium tin oxide, provides hole transporting properties. Polarised green electroluminescence was obtained by spin coating a novel polymerisable and light-emitting liquid crystal onto the photoaligned copolymer. A polarisation ratio value of 13 : 1 and a polarised irradiance of 200 cd m−2 was obtained at 9 V. Polarised red emission is also described in a guest–host configuration. The spatial patterning of the polarisation direction is also shown.

All-optical modulation of a spiropyran-based device, integrating the transmittance switching (absorption) and wavelength modulation (emission) of visible light frequency induced by alternating UV/visible light irradiation is demonstrated. As an alternative to conventional organic transistors, all-optical devices based on SP-PCL have potential utility as single molecular transistors for optical switching and visible wavelength modulation.

We report the design, synthesis and optical properties of a fluorescent HABI-based photochrome, which exhibits high fluorescence quantum yield (ΦF = 25%) and efficient quenching in the dissociated state. Efficient contrast fluorescence switching and good reversibility are also demonstrated. We demonstrate the merits of a non-conjugated design strategy for fluorescent HABIs.

Phenanthroline–tetraphenylethene (Phen–1TPE) was synthesized by a typical Suzuki coupling. The aggregation-induced emission (AIE) properties and interactions with metal ions in THF–water (fw = 90%) and in THF were investigated. Aggregation-induced emission logic gates were fabricated based on the metal ion sensing of Phen–1TPE conjugates via control of the metal ions and solvents. In THF–water with fw = 90%, Phen–1TPE exhibits a strong AIE effect, while the fluorescence is almost totally quenched upon the addition of Cu2+ compared to other metal ions. Phen–1TPE works as an “INHIBIT” logic gate, with Cu2+ and aggregation (“Agg”) as the inputs and the fluorescence as the output. The fluorescence can also be quenched in fw = 90% by the addition of metal ions (Cd2+, Zn2+, Sn2+ and In3+). In THF, Phen–1TPE exhibits a metal ion–ligand charge transfer (MLCT)-caused fluorescence enhancement by the addition of metal ions (Cd2+, Zn2+, Sn2+ and In3+). Thus it is established that Phen–1TPE works as a dual “XOR” logic gate with metal ions (Cd2+, Zn2+, Sn2+ and In3+) and “Agg” as the inputs. The INHIBIT and XOR logic gates were manipulated by utilizing different metal ions and water–THF volume ratios as the inputs, and the fluorescence of Phen–1TPE as the output.

In recent years low molecular weight carbazole-based materials have attracted much interest as hole-transporting and host materials for organic light emitting diode (OLED) applications. Herein we report the tri- and tetra-bromination of carbazole and the subsequent synthesis of novel carbazole oligomers substituted at the 1- and 8-positions. The oligomer series range from mono-carbazole (Cz-1) to quinque-carbazole (Cz-5) and we have carried out a comparative study of their thermal, optical, electrochemical and optoelectronic properties. The glass transition temperature increases as the carbazole core is enlarged (0 °C to 54 °C) and all oligomers exhibit excellent thermal stability with high thermal decomposition temperatures in the range of 442 °C to 494 °C. From optical data and Raman spectroscopy we observe negligible changes in the effective conjugation length as the number of peripheral carbazole units increases. However, the oxidation potential decreases as the number of carbazole units increase, in which Cz-5 exhibits the highest HOMO level (−5.19 eV) compared to other carbazole oligomers in the series. All carbazole materials emit deep blue photoluminescence ranging from 416 to 432 nm in the solid-state. Finally, electrophosphorescence was demonstrated from solution processable guest-host organic light- emitting diodes (OLEDs) fabricated using Cz(2–5) as the host materials with device configuration ITO/PEDOT/Cz1–5 : 10% Ir(mppy)3/TPBi/LiF/Al. The device efficiency decreases from Cz-3 to Cz-5. The best OLED device that incorporates Cz-3 as the host exhibits a turn-on voltage of 2.8 V, maximum brightness of 2310 cd m−2, maximum power efficiency of 33.6 lm W−1, maximum current efficiency 35.5 cd A−1 and EQE of 10.6%.

Two novel simple electron-transport (ET) type host materials, 2,6-bis(3-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)benzene (MDBIP) and 2,6-bis(3-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)pyridine (MDBIPy) have been designed and synthesized. The two compounds exhibit high decomposition temperatures (Td: 444 °C for MDBIP and 450 °C for MDBIPy) and a stable amorphous glassy state (Tg: 108 °C for MDBIP and 110 °C for MDBIPy). In the typical device ITO/MoO3 (10 nm)/4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB, 80 nm)/TCTA (5 nm)/Host: Ir(ppy)3 (9 wt%, 20 nm)/TmPyPB (40 nm)/LiF (1 nm)/Al (100 nm), when MDBIPy was used as host material, the device B showed a maximum efficiency of 21.1%, 75.8 cd A−1 and 83.6 lm W−1. When MDBIPy was utilized as both the electron transporting and host layer, the unilateral homogeneous device C exhibited a maximum efficiency of 20.6%, 74.2 cd A−1 and 71.8 lm W−1. More interestingly, device C showed low efficiency roll-off relative to device B. When the brightness of the device is over 1000 cd m−2, the current efficiency of device C is higher than device B. At a brightness of 5000 cd m−2, the current efficiency of device C is only roll off 5.6%. These results demonstrate that utilizing electron-transport type host materials to fabricate unilateral homogeneous PhOLEDs is a promising way to simplify the device configuration and optimize the performance of OLED devices.

We report the synthesis of novel amorphous fluorene-based fluorophores that have been end-capped with tetraphenylethene (TPE). Although in the solid state the fluorophores show bright cyan fluorescence with high (68%) photoluminescence quantum efficiency (PLQE), strong fluorescence quenching is observed in solution with low PLQE values ranging from 0.3% to 2.1%. When the fluorophores were added to a 90% water–THF solvent mixture nanoparticles were formed, which was confirmed by Dynamic Light Scattering (DLS) and Atomic Force Microscopy (AFM). Subsequent fluorescence measurements reveal that all the fluorophores exhibit aggregation induced emission (AIE) with high PLQE (41%). We have carried out a comparative study of 5 fluorene-based TPE materials (F(1–5)TPE), in which the fluorene core is extended, and investigated their thermal, optical, electrochemical and electroluminescence properties. From fluorescence quantum yield data we have discovered that the AIE effect decreases as the fluorene core increases both in the nanoparticle and in the solid state. Thermal analysis reveals that all fluorophores are amorphous with high thermal stabilities. Potential application in solid state vapour sensing has been demonstrated using dichloromethane that shows “on” and “off” fluorescence behaviour. Finally, Organic Light Emitting Diodes (OLEDs) have been fabricated with device configuration ITO/PEDOT/F(1–5)TPE/TPBi/LiF/Al. The best OLED device that incorporates F1-TPE as the emitter exhibits a turn-on voltage of 5.8 V, Lmax = 1300 cd m−2, ηP,max = 1 lm W−1 and ηC,max = 2.6 cd A−1.