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In this report, an LCMLA with a negative-positive tunable focal length is designed using a self-assembled highly uniform polymer convex array. The polymer convex array was prepared by scribing UV-s...

Both random laser and multimode band-edge laser have been found in cholesteric liquid crystals (CLCs). In this work, the laser emission in CLC with negative dielectric anisotropy under electric fie...

In this study, low driving voltage liquid crystal microlens array (LCMLA) based on polyvinyl alcohol (PVA) convex array was fabricated by facile method. The PVA convex array served as a vertical al...

Electrically tunable random laser action has been demonstrated in a cavity-free structure. The scattering structure was shaped by the treatment of AC, and a polymer network structure is introduced ...

Unipolar n-type conjugated polymer materials with long-term stable electron transport upon direct exposure to the air atmosphere are very challenging to prepare. In this study, three unipolar n-type donor-acceptor (D-A) conjugated polymer semiconductors (abbreviated as PNVB, PBABDFV, and PBAIDV) were successfully developed through a "strong acceptor-weak donor" strategy. The weak electron donation of the donor units in all three polymers successfully lowered the molecular energy levels by the acceptor units that strongly attracted electrons. Cyclic voltammetry demonstrated that all three polymers had low highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels near -6.0 and -4.0 eV, respectively. These results were consistent with the density functional theory calculations. The as-prepared polymers were then used to manufacture organic field-effect transistor (OFET) devices in bottom-gate/top-contact (BG/TC) configuration without any packaging protection. As expected, all devices exhibited unipolar electron transport properties. PBABDFV-based devices showed excellent field-effect performance and air stability, beneficial for straight-line molecular chain and closest π-π stacking distance to prevent water vapor and oxygen from diffusion into the active layer. This led to a maximum electron mobility (μe,max) of 0.79 cm2 V-1 s-1 under air conditions. In addition, 0.50 cm2 V-1 s-1 was still maintained after 27 days of storage in ambient environment. The near-ideal transfer curve of the PBABDFV-based OFET device in BG/TC configuration under vacuum was obtained with average mobility reliability factor (rave) reaching 88%.

We report a microlens array with a controllable focal length that is based on a selective wetting surface. A substrate modified with a hydrophobic layer that has an array of microholes exhibits different wettability for inside holes (hydrophilic) versus outside holes (hydrophobic). When liquid flows over the surface, a small amount of liquid is adhered to hydrophilic holes and forms a lens-shaped droplet array that self-assembles because of surface tension. A large-sized plano-convex lens array that has good uniformity is obtained via the blade coating method, and controlling the amount of liquid enables control of the focal length. Our self-assembled microlens array has the merits of high optical performance, a simple fabrication procedure, and good mechanical stability, and thus, it has potential applications in imaging processing, light extraction, protein detection, light-emitting diodes, sensors, and displays.

The fate of arsenic sulfide sludge (ASS), a typical precipitationproduct of acid smelting wastewater, is readily affected by the surrounding conditions when deposited in environment. When exposed to sunlight, the dissolution and oxidation of ASS were markedly accelerated. However, the photocatalytic transformation mechanism of ASS is still unclear. Herein, the release and oxidation of As(III) in ASS under visible light was investigated by employing artificial arsenic sulfide with Fe(II)/Fe(III) ions. Results show that the coexisting ferric ions are critical to promote the photo-oxidation of As(III) released from the parental solid into As(V). The photo-oxidation rate can reach 149 μM/h in the presence of 0.5 mM Fe(II) ions at pH 1.3, ~5 times of that in the absence of Fe(II). The pH-dependent mechanism of photocatalytic oxidation of As(III) stimulated by Fe(II) ions is proposed and verified. In acid conditions (pH 1.3 and 3), photo-generated hydroxyl and sulfate radicals were promoted by Fe(II)/Fe(III) cycling catalysis with the assistance of the reductive sulfur species from ASS, e.g. S2-and SO32-, and thus accelerated the oxidation of As(III). While at pH 7, the nascent ferric hydroxide colloids enhanced the oxidation rate of As(III) via photo-induced ligand-to-metal-charge transfer (LMCT) mechanism. These findings can help in predicting and controlling the fate of real arsenic-containing sludge in sunlit environments.

Arsenic containing sludge, a product of the treatment of acid smelting wastewater, is susceptible to temperature, pH, co-existing salt ions and organic matter, which might lead to the release of arsenic ions into the environment. Here, we studied the effect of visible light on the dissolution and oxidation of arsenic sulfide sludge (ASS) sampled from a smelting plant. Results show that by exposure to visible light, both the release of As(III) ions from ASS and the oxidation of As(III) into As(V) were markedly accelerated. Electron paramagnetic resonance (EPR) and free radical quenching experiments revealed that ASS acts as a semiconductor photocatalyst to produce hydroxide and superoxide free radicals under visible light. At pH 7 and 11, both the dissolution and the oxidation of the sludge are directly accelerated by O2¯. At pH 3, the dissolution of the sludge is promoted by both O2¯ and OH, while the oxidation of As(III) is mainly controlled by OH. In addition, the solid phase of ASS was transformed to sulfur (S8) which favored the aggregation and precipitation of the sludge. The transformation was affected by the generation of intermediate sulfur species and sulfur-containing free radicals, as determined by ion chromatography and low-temperature EPR, respectively. A photocatalytic oxidation-based model is proposed to underpin the As(III) release and oxidation behavior of ASS under visible light conditions. This study helps to predict the fate of ASS deposited in the environment in a range of natural and engineered settings.

In order to produce liquid crystal (LC) with high birefringence (Δn) in the THz band, eight LC monomers were designed and synthesized. We formulate two mixtures (LC S200-2 and E7-2) by addi...

We report on the study of 1.0 eV InGaAsP solar cells grown by metalorganic vapor phase epitaxy (MOVPE) on InP. Under standard one-sun air-mass 0 (AM0) illumination, InGaAsP single junction solar cell grown at temperature 650 °C presents remarkable photovoltaic performance. With further growth improvements, solar cell presents an efficiency of 19.1% with an open-circuit voltage (Voc) of 693 mV. The experimental bandgap-voltage offset (Woc) as low as 325 mV is achieved, approaching its theoretical value predicted using diffusion-limited model.

A new π-extended electron-deficient unit, 6,6′-(5,5′-N,N’-(2-ethylhexyl)-isoindigo-6,6′-diyl)bis(thiophene-5,2-diyl))bis(2,5-bis(2-decyltetradecyl)-3-(thiophen-2-yl)pyrrolo[3,4-c]-pyrrole −1,4 (2H,5H)-dione) (2DPPI) was designed and synthesized. Three new D-A conjugated polymers were then synthesized based on 2DPPI unit and different electron-donors thiophene, thieno[3,2-b]thiophene and 2,2′-bithiophene. Their photophysical properties, electrochemical behaviors, field-effect characteristics, thin-films morphologies, and photothermal conversion performances were systematically investigated. All three polymers displayed broad and strong absorption in the near infrared region. Compared with the corresponding DPP-based polymers, the 2DPPI-based polymers possess deeper the highest occupied molecular orbital and the lowest unoccupied molecular orbital levels and narrower band gap due to the introduction of large acceptor formed by IID and DPP. The OTFT devices based on three polymers were fabricated, and their field-effect performance were characterized under ambient conditions. After annealing, P2DPP-BT showed the maximum hole mobility of 0.224 cm2 V −1 s −1 and an electron mobility of 0.033 cm2 V −1 s −1. The corresponding microstructure and morphology analyses revealed that P2DPPI-BT showed more ordered molecular stacking, lamellar packing and well-interconnected larger domains, all of which are favorable to the carrier transport. In addition, the photothermal test reviews that all three polymer films can effectively convert near infrared light to heat, and P2DPPI-TT has the highest photothermal conversion efficiency of 25.6%. Furthermore, P2DPPI-TT was successfully used for tuning cholesteric liquid crystal reflective band under the irradiation of near infrared light.

Although various donor–acceptor (D–A) small molecules with high power conversion efficiency have been reported, D–A small molecules with high field-effect mobility are still rare. In this work, two new A–D–A small molecules with a rigid indacenodithieno[3,2-b]thiophene (IDTT) moiety as the central core and both ends capped with strong electron-withdrawing indole-2,3-dione (IDD) and N-substituted pyrrolo[2,3-b]pyridine-2,3-dione (IDD-N) were synthesized and characterized for applications in solution-processable organic field-effect transistors (OFETs). A N atom was introduced to the IDD units to enhance the planarity and structural ordering by noncovalent interactions, leading to a dramatic effect on the small molecule. The unsubstituted small molecule (IDTT–IDD) did not show any field-effect performance, whereas an encouraging hole mobility of 7.7 cm2 V–1 s–1 with an average mobility of 6.1 cm2 V–1 s–1 was obtained for solution-processable OFETs based on the N-substituted one (IDTT–IDD-N). This work provi...

Six donor–acceptor (D–A) conjugated polymers, P1–P6, based on the novel electron acceptors bis-isoindigo (BIID) and bis-azaisoindigo (BAID), were designed and synthesized for solution-processed organic field-effect transistors with high-performance optical and electrical properties. Energy level regulation was achieved by incorporation of nitrogen and fluorine heteroatoms and side chain optimization to reduce side chain density and extend branching point positions. Both the hole (μh) and electron mobilities (μe) significantly increased from P1 to P6, and there was an obvious transition from hole-dominated ambipolar charge transport behavior to highly-balanced ambipolar behavior. Since aza-substitution strengthened the electron-deficient property of the acceptor units, the entire molecular skeleton of BAID-based polymers has a high electron affinity and a low-lying lowest unoccupied molecular orbital (LUMO) level according to ultraviolet photoelectron spectroscopy (UPS) and cyclic voltammetry (CV) measurements. The μe of BAID-based polymers is an order of magnitude higher than that of BIID-based polymers. In addition, side chain optimization was shown to significantly influence intermolecular interactions and supramolecular self-assembly. The stepwise reduction of the π–π stacking distances of P1–P6 calculated by GIXRD curves supports this conclusion. Finally, in P6 (PBAID3-2FBT), a maximum absorption wavelength (λmax) was observed at 797 nm, a low optical band gap (Eg) of 1.27 eV, a low LUMO level of −3.90 eV, and an average μh and μe of 1.31 cm2 V−1 s−1. This paper offers an available molecular design strategy to achieve highly-balanced and high-performance ambipolar charge carrier transport D–A conjugated polymers.

A conjugated polymer based on naphthalene-diimide and dithiophene units was synthesized by continuous flow synthesis. Due to the large specific surface area and excellent heat transfer, the polymerization was completed within ∼35 min at 110 °C. Compared to flask synthesis, the continuous flow technology exhibited a high synthesis efficiency and significant reduction in reaction times. The polymer using flow synthesis exhibited higher molecular weight (17.28/35.27 vs. 4.86/13.21 kg mol−1), lower polydispersity indexes (2.0 vs. 2.7), and a more ordered crystalline structure. Consequently, much higher electron mobilities (0.74 vs. 0.11 cm2 V−1 s−1) with Ion/Ioff ratios of 106 were obtained for the polymer using flow synthesis. This study demonstrates that continuous flow synthesis will be promising in the preparation of conjugated polymers with high efficiency.

Photovoltaic power generation, as a rapidly growing new energy source, is a technology that uses a semiconductor to convert light energy into electrical energy. Sb2S3 solar cells possess the advantages of simple binary components, abundant resources, nontoxicity, and excellent stability; they have recently attracted extensive investigation interest. Various strategies, such as solution and vacuum deposition, have been used to fabricate functional layers, including Sb2S3 photoactive layers, electron transport layers and hole transport layers. Here, we briefly review the preparation methodologies, morphologies, structures, optoelectronic properties and the corresponding solar cell performance of functional layers for both planar heterojunction solar cells and mesoporous sensitized solar cells. Some viewpoints of further improvement of Sb2S3 solar cell conversion efficiency from the aspect of material fabrication and modification are given.

Achieving good electrical properties and ductility of polymer semiconductors has always been challenging. In this work, a series of isoindigo derivative-based conjugated polymers was studied in an effort to gain a better understanding of the influence of polymer main and side chain structures on their electrical and mechanical properties. The results suggested that the introduction of alkyl side chains onto the donors can significantly enhance the mechanical properties of isoindigo-based polymers; however, the electrical properties of the films greatly deteriorated due to the large steric hindrance by the chain. The insertion of strong electron-withdrawing units, such as benzodifurandione, into the isoindigo chain during the synthesis of a bis(2-oxoindolin-3-ylidene)-benzodifuran-dione (BIBDF)-based polymer (PBIBDF-BT) significantly boosted the electrical properties of the films without decreasing their mechanical properties. The crack onset in PBIBDF-BT thin films was observed at 50% tensile strain. In addition, PBIBDF-BT thin films exhibited bipolar transport properties with both electron and hole mobilities greater than 0.1 cm2 V−1 s−1 at 100% strain. It is found that the improvement of PBIBDF-BT performance is attributed to its proper molecular structure. The long alkyl side chains significantly increase the ductility of PBIBDF-BT thin films, and the strong electron-withdrawing BIBDF unit in the main chains enhances the local aggregation, resulting in a significant increase in mobility. These results indicate that the mechanical and electrical properties of conjugated polymers could simultaneously be improved through reasonable molecular design.

A new strongly electron-deficient acceptor unit, (3E, 7E)-3,7-bis(6-bromo-7-aza-2-oxoindolin-3-ylidene)-5,7-dihydropyrrolo [2,3-f] indole-2,6(1H,3H)-dione (BADDP, Fig. 1), was designed and synthesized for the first time. Two donor−acceptor (D−A) conjugated polymers, namely P1 and P2, were also synthesized using the new strongly electron-withdrawing unit as the acceptor and thieno [3,2-b]thiophene (TT) and (E)-2-(2-(thiophen-2-yl)vinyl)thiophene (TVT) as the donor units. Their thermal, photophysical, microstructural, and field-effect properties were systematically investigated. Both the polymers with deep lowest unoccupied molecular orbital (LUMO) energy levels (approximately −3.9 eV) for marching with electron transport showed n-type charge transport characteristics with an electron mobility of 0.18 cm2 V−1 s−1 under vacuum conditions. Moreover, ambipolar behavior was also obtained with a hole mobility of up to 0.20 cm2 V−1 s−1 and an electron mobility of up to 5.8 × 10−2 cm2 V−1 s−1 when exposed to air.

l -Histidine (L-His) is an essential bioactive amino acid, playing a significant role in several biological processes. Therefore, the accurate determination of L-His is of great significance to human health. In this work, a strategy was developed for the chiral detection of L-His using an organic electrochemical transistor (OECT) sensor based on molecularly imprinted polymer (MIP). MIP films were electrodeposited on OECT gate platforms. MIP films designed for specifically recognizing His combined with the amplified function of an OECT yielded highly sensitive and selective OECT biosensor. The properties of the resulting biosensor were characterized by various analytical methods. The results indicated that changes in channel current was proportional to D-His and L-His concentrations from 100 nM to 10 μM, with the detection limits of 10 nM and 100 nM (S/N > 3), respectively. Furthermore, the highly selective MIP film allowed to differentiate L-His from D-His or D-His from L-His. In terms of selectivity, the tests suggested apparent differences in channel current changes between L-His and D-His and interferences. The applicability of the biosensor for L-His detection in human urine demonstrated this sensor will be ideal transducers for disposable applications in the future.

CsPbBr3/SiO2 perovskite quantum dots (PQDs), which exhibit good stability in water, air, and light, are synthesised using the water-trigger method. Due to the interaction between the long alkyl ligands of the PQDs and the liquid crystal, the liquid-crystal molecules prefer to align perpendicular to the surface of the PQDs, which disturbs the liquid crystal order and decreases its clearing point. The effect of CsPbBr3/SiO2 PQDs on the electro-optical properties and physical parameters of a nematic liquid crystal are investigated. The dielectric anisotropy (Δε) and splay elastic constant (K11) decrease substantially with increasing concentration of PQDs. PQDs, which are doped into the liquid crystal, can effectively reduce the threshold voltage (Vth), which opens possibilities to reduce energy consumption in many optoelectronic devices.

Developing nonchlorinated solvent-processed polymeric semiconductors to avoid environmental concerns and health hazards caused by chlorinated solvents is especially urgent. Here, a molecular design strategy, composed of backbone fluorination and side chain optimization, is used for preparing high-solubility and high-performance azaisoindigo-based polymers. The effects of different backbones and side chains on the solubility, film crystallinity, molecular stacking, and charge transport properties are mainly investigated. A long linear hybrid siloxane-based chain (C

In the previous work, two new nematic liquid crystal (NLC) mixtures, E7-2 and S200-2, were produced by adding eight LC monomers to two commercial LCs S200 and E7, respectively. At &lambda, = 589 nm, the birefringence (&Delta, n) characteristics of the two LC nematic mixtures E7-2 (&Delta, n = 0.260) and S200-2 (&Delta, n = 0.298) are greater than those of the commercial LC E7 (&Delta, n = 0.224) and S200 (&Delta, n = 0.266). The properties (TN-I, &epsilon, //, &Delta, ɛ, K11, and K33) of these four NLCs were measured. A double-layer metal loop arrays modulation structure based on metamaterial (MM) metal&ndash, dielectric&ndash, metal (MDM) was designed and fabricated for use in the THz frequency range. The results show that the LC mixtures E7-2 and S200-2 have greater modulation depth (MD) and less modulation insertion loss (IL) than E7 and S200 at THz frequencies. The results show that LC mixtures have significant potential for designing active tunable LC-based devices in the THz and visible light range.

Radiation-induced defects are responsible for solar cell degradation. The effects of radiation and annealing on the defects of a GaAs/Ge solar cell are modeled and analyzed in this paper. The electrical performance and spectral response of solar cells irradiated with 150 keV proton are examined. Then, thermal annealing was carried out at 120°C. We found that the proportion of defect recovery after annealing decreases with increasing irradiation fluence. The minority carrier lifetime increases with decreasing defect concentration, which means that the electrical performance of the solar cell is improved. We calculated the defect concentration and minority carrier lifetime with numerical simulation and modeled an improved annealing kinetic equation with experimental results.

Flexible and low-voltage near-infrared organic phototransistors (NIR OPTs) were prepared with a low-band gap donor–acceptor conjugated polymer as the semiconductor layer and n-octadecyl phosphonic acid modified anodic alumina (AlOx/ODPA) as the insulating layer. The phototransistors exhibit the typical n-type transistor characteristics at a voltage below 5 V. The photosensitivity of phototransistors can be enhanced by regulating the packing densities of the ODPA self-assembled monolayers and forming different trap states. The enhanced OPTs exhibit good photosensitivity to 808–980 nm NIR with the photocurrent/dark current ratio and photoresponsivity as high as 5 × 103 and 20 mA W–1, respectively, benefiting from the charge-trapping effect at the AlOx/ODPA interface. The OPTs also present a fast optical switching speed of 20/30 ms and an excellent mechanical flexibility. The outstanding performance of the NIR OPTs indicates that the development of wearable electronics is, indeed, possible.

In this paper, a nematic liquid crystal (NLC)-based tunable terahertz (THz) plasmonic metamaterials (MMs) with large modulation depth (MD) and low insertion loss (IL) is designed and experimentally verified at THz frequencies. The proposed structure includes two-layered MM that is immersed in LC. The metal MM is used directly as electrode. The tunable device with a 46×46 array of sub-wavelength circular air loops was fabricated on a quartz glass substrate, with 2×2 cm2 area and 220 µm thickness. The obtained results show that the amplitude MD and IL for normally incident electromagnetic (EM) waves are about 96% and 1.19 dB at 421.2 GHz, respectively, when the bias voltage applied to the NLC layer varies from 0 to 16 V. Meanwhile, the transmission peak frequency gradually decreases from 421.2 to 381.8 GHz, and the frequency tunability (FT) of the proposed structure is greater than 9.35%. This study provides a potential solution for THz modulators, filters, and switches.

Conjugated polymer-based organic thin film transistors (OTFTs) have received tremendous attention due to their potential applications. In addition to their high performances, air stability is also ...

Organic field-effect transistors (OFETs) without any encapsulation of polymer semiconductor layers that still exhibit unipolar n-type characteristics under air conditions are very rare. In this study, we use fluorinated bithiophene as a donor, and bis(2-oxoindolin-3-ylidene)-benzodifuran-dione (BIBDF, P1) and aza-substituted BIBDF (P2) as acceptor units to develop air-stable and unipolar electron transport polymer semiconductors. Unencapsulated OFETs based on P1 and P2 were fabricated and directly evaluated under air conditions. The highest effective mobility (μe,maxeff) of 0.23 cm2 V–1 s–1 was obtained for P2-based devices with high Ion/Ioff ratio of >106 and low threshold voltage of 1.1 V. Moreover, P2 had high air stability and maintained unipolar electron transport with μe,maxeff of up 0.1 cm2 V–1 s–1 and Ion/Ioff ratio of >106 during the 60 days of air storage. The work provides an effective molecular design strategy to develop air-stable and high-performance n-channel unencapsulated polymer transist...

One-step deposition of bi-functional semiconductor-dielectric layers for organic field-effect transistors (OFETs) is an effective way to simplify the device fabrication. However, the proposed method has rarely been reported in large-area flexible organic electronics. Herein, we demonstrate wafer-scale OFETs by bar coating the semiconducting and insulating polymer blend solution in one-step. The semiconducting polymer poly(3-hexylthiophene) (P3HT) segregates on top of the blend film, whereas dielectric polymethyl methacrylate (PMMA) acts as the bottom layer, which is achieved by a vertical phase separation structure. The morphology of blend film can be controlled by varying the concentration of P3HT and PMMA solutions. The wafer-scale one-step OFETs, with a continuous ultrathin P3HT film of 2.7 nm, exhibit high electrical reproducibility and uniformity. The one-step OFETs extend to substrate-free arrays that can be attached everywhere on varying substrates. In addition, because of the well-ordered molecular arrangement, the moderate charge transport pathway is formed, which resulted in stable OFETs under various organic solvent vapors and lights of different wavelengths. The results demonstrate that the one-step OFETs have promising potential in the field of large-area organic wearable electronics.

Chiral recognition of α-amino acids is attracting increasing interest due to the importance of α-amino acids in protein metabolism as well as in food products and pharmaceuticals. Organic electrochemical transistors (OECTs) with gate electrodes modified with molecularly imprinted polymer (MIP) films were fabricated and successfully used as highly selective and sensitive chiral recognition biosensors for d/l -tryptophan ( d / l -Trp) and d/l -tyrosine ( d / l -Tyr). The MIP films, which can specifically recognize and has an electrocatalytic effect on the oxidation of Trp and Tyr, together with the amplification function of an OECT, provide a highly sensitive and selective OECT biosensor. The sensor showed a linear response range for l -Trp and L -Tyr from 300 nM to 10 μM with a sensitivity of 3.19 and 3.64 μA/μM, respectivity. And the detection limit for L -Trp and L -Tyr is of 2 nM and 30 nM (S/N > 3). The selectivity factors of L -Trp, D -Trp, L -Tyr and D -Tyr to their enantiomers are 11.6, 3.5, 14.5 and 2.6, respectively. This method can pave the way for widespread applications of OECT-based sensors in chiral material identification.

In this study, an organic electrochemical transistor sensor (OECT) with a molecularly imprinted polymer (MIP)-modified gate electrode was prepared for the detection of ascorbic acid (AA). The combination of the amplification function of an OECT and the selective specificity of MIPs afforded a highly sensitive, selective OECT sensor. Cyclic voltammetry and electrochemical impedance spectroscopy measurements were carried out to monitor the stepwise fabrication of the modified electrodes and the adsorption capacity of the MIP/Au electrodes. Atomic force microscopy was employed for examining the surface morphology of the electrodes. Important detection parameters, pH and detection temperature were optimized. With the change in the relative concentration of AA from 1μM to 100μM, the MIP-OECT sensor exhibited a low detection limit of 10nM (S/N > 3) and a sensitivity of 75.3μA channel current change per decade under optimal conditions. In addition, the MIP-OECT sensor exhibited excellent specific recognition ability to AA, which prevented the interference from other structurally similar compounds (e.g., aspartic acid, glucose, uric acid, glycine, glutathione, H2O2), and common metal ions (K+, Na+, Ca2+, Mg2+, and Fe2+). In addition, a series of vitamin C beverages were analyzed to demonstrate the feasibility of the MIP-OECT sensor. Using the proposed principle, several other sensors with improved performance can be constructed via the modification of organic electrochemical transistors with appropriate MIP films.

Conjugated polymers have received tremendous attention because of their potential application in flexible electronic devices. In addition to synthesizing new conjugated polymers, different methods have been used to improve charge carrier transport. The simple random polymer strategy was used to enhance the charge carrier mobility of isoindigo (ID)-based conjugated polymers by chemically blending a small amount of strongly electron-deficient bis(2-oxoindolin-3-ylidene)benzodifurandione (BIBDF) units. In comparison with a parent polymer (P0) without BIBDF in its polymer backbone, the hole mobilities of random polymers were remarkably enhanced by the chemical blending of BIBDF with low content (

In this paper, a liquid crystal (LC) based tunable metamaterial absorber with dual-band absorption is presented. The proposed absorber is analysed both numerically and experimentally. The analysis shows that the two absorption peaks, originating from the new resonant structure, are experimentally detected at 269.8 GHz and 301.4 GHz when no bias voltage is applied to the LC layer. In order to understand the absorption mechanisms, simulation results for the surface current and power loss distributions are presented. Since liquid crystals are used as the dielectric layer to realize the electrically tunable absorber, a frequency tunability of 2.45% and 3.65% for the two absorption peaks is experimentally demonstrated by changing the bias voltage of the LC layer from 0 V to 12 V. Furthermore, the absorber is polarization independent and a high absorption for a wide range of oblique incidence is achieved. The designed absorber provides a way forward for the realization of tunable metamaterial devices that can be applied in multi-band detection and imaging.

A series of P3HT-b-PHA-b-P3HT tri-block and P3HT-b-PHA di-block copolymers were facilely synthesized in one pot. The influence of the block ratio on the optical, microstructural and electrical properties has been investigated. OFETs based on these block copolymers have been fabricated with an improved mobility of 0.052 cm2 V−1 s−1via a blending method.

A new thieno-isoindigo derivative, (3E,7E)-3,7-bis(4-(2-decyltetradecyl)-4H-thieno[3,2-b]pyrrole-5,6-dione)-5,7-dihydropyrrolo[2,3-f]indole-2,6(1H,3H)-dione (BTPDI), was designed and synthesized. A donor−acceptor conjugated polymer (PBTPDI-TT) was also synthesized with this new unit as the acceptor and thieno[3,2-b]thiophene as the donor. The microstructure, photophysical, electrochemical, field-effect properties and photothermal performances were investigated. The polymer showed a broad absorption spectrum that spanned across the near-infrared (NIR) region (780–1300 nm), with a very low bandgap (∼0.95 eV), deep lowest unoccupied molecular orbital, and suitable highest occupied molecular orbital levels. As a result, the polymer-based organic field-effect transistors showed highly balanced hole and electron transport characteristics with a hole mobility of 0.027 cm2 V−1s−1 and an electron mobility of 0.022 cm2 V−1s−1. The polymer nanoparticles showed good reusability under NIR (980 nm) irradiation and could also effectively convert NIR light to heat at an excellent efficiency of 20.3%.

Luminescent liquid crystals (LLCs) have attracted significant interest for organic optoelectronic applications, especially for the generation of linear polarized light. Here, a novel LLC molecule, 2-(4-(nonanealkoxy)phenyl)-3-(4-formamidephenyl)-acrylonitrile (CN-NPFA), is reported, which shows strong fluorescence in the solid state due to the aggregation-induced enhanced emission (AIEE) effect. Moreover, a well-aligned liquid crystalline film using AIEE-active molecules, is obtained using an in-plane electric field with an alignment layer. It exhibits highly polarized luminescence ( ρ = 0.74) with a high fluorescence quantum yield. The device is both cheap and easy to fabricate, and has the potential to be used in practical electro-optic applications.

Light-emitting liquid crystal displays (LE-LCDs), serving as emissive displays, are considered as promising alternatives to conventional LCDs because of their superior power efficiency. A dichroic fluorescent dye (Z)-2-(4-aminophenyl)-3-(4-(fluorophenyl)acrylonitrile (CN-AFAN) is synthesised, which exhibits strong fluorescence in the solution and solid states. Moreover, an electrically switchable optical switch based on CN-AFAN and a cholesteric liquid crystal is demonstrated, which combines the internal scattering of excitation light and the dichroism of CN-AFAN to improve fluorescence contrast. The photoluminescence and transmittance of the optical switch is modulated by an electric field between the planar state, focal conic state, and homeotropic state. The resultant device is cost-effective and easy to fabricate, thereby demonstrating immense potential for security and display applications.

Two new D−A polymers ( PBTPBF-HH and PBTPBF-TT ) based on (3 E , 7 E )-3,7-bis(4-(2-decyltetradecyl)-4 H -thieno[3,2- b ]pyrrole-5,6-dione)benzo[1,2- b :4,5- b' ]difuran-2,6(3 H ,7 H )-dione and ( E )-2-(2-(thiophen-2-yl)vinyl)thiophene units with different side-chain positions (head-to-head and tail-to-tail) were synthesized, and the side-chain positions were optimized with respect to their planarity, microstructure and performance as organic thin-film transistors. Both the polymers showed broad absorption spectra (covering 400–1600 nm) and remarkably low bandgaps (ca. 0.8 eV). PBTPBF-HH containing head-to-head linkages had a dual texture, in which face-on and edge-on crystallites coexisted. In contrast, PBTPBF-TT containing tail-to-tail linkages mainly exhibited an edge-on texture. Consequently, PBTPBF-TT showed a much higher transport performance than PBTPBF-HH when evaluated using bottom-gate/top-contact organic thin-film transistors. The best mobilities of above 0.80 cm 2 V −1 s −1 and 0.19 cm 2 V −1 s −1 were obtained for hole and electron, respectively, at the optimized thermal annealing and in the presence of a high boiling point additive. Overall, this study showed that a minimal change in their side-chain positions dramatically optimized the planarity, microstructure, π-stacking orientation, and charge transport performance.

A stripping procedure was demonstrated for the preparation of an ultra-smooth aluminum electrode. After potentiostatic anodization and treatment with a self-assembled monolayer (SAM) of n-octadecyl phosphonic acid, AlOx–SAM hybrid dielectrics were grown onto flexible, stripped aluminum combining low cost manufacture under ambient conditions with excellent dielectric characteristics (negligible leakage, 114.3 nF cm−2 capacitance). Field effect transistors using dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) as an organic semiconductor can be operated below −5 V with a high mobility of 0.53 cm2 V−1 s−1, high on/off current ratio of 1.7 × 105, low subthreshold slope of 210 mV dec−1, and good threshold of −1.51 V. Moreover, the DNTT transistor showed a good photoresponse to blue light with a wavelength of 450 nm, with photoresponsivity (R) of 50 A W−1 and a photocurrent/dark current ratio (P) of 5 at a light intensity of 5 μW cm−2.

A tunable metamaterial absorber based on the liquid crystal intended for F frequency band is presented. The proposed absorber was analyzed both numerically and experimentally. The conducted analysis has shown that the bias voltage affects the orientation of the nematic liquid crystal embedded in the mesh voids and causes the resonant frequency shift from 110.9 to 103.8 GHz with the frequency tunability of 6.4%. The absorptivity of the proposed absorber was measured, and it was higher than 90% for all bias voltages. Therefore, the proposed absorber provides a new opportunity in development of tunable sensors and absorbers.

The aldol reaction is a facile green synthetic method and has been widely used in the synthesis of small molecules. In this study, we attempted to prepare conjugated polymers using aldol polymerization for the first time. Two isoindigo-based conjugated polymers (PIID-DT and PBIBDF-DT) were synthesized successfully in excellent yields and with high molecular weights (MGPCn up to 53.9 kDa) using toluene as the solvent and an acid as the catalyst. The entire synthesis route is economical and environmentally friendly, and the traditional drawbacks such as the use of organometallic reagents, toxic tin monomers, and other environmentally harmful compounds often encountered in Stille and Suzuki cross-coupling reactions could be avoided. Moreover, the isoindigo-based polymers prepared by the newly established aldol polymerization were also evaluated as organic field-effect transistors with bottom-gate/top-contact devices and exhibited excellent mobilities as high as 0.16 and 0.26 cm2 V−1 s−1 with a high Ion/Ioff ratio of 105 for PIID-DT and PBIBDF-DT, respectively. Therefore, aldol polycondensation has environmentally friendly characteristics that can be applied in the green synthesis of isoindigo-based conjugated polymers.

It is highly desired that synthesis of photothermal agents with near-infrared (NIR) absorption, excellent photostability, and high photothermal conversion efficiency are needed for potential applications. Three (D-A) conjugated polymers (PBABDF-BDTT, PBABDF-BT, and PBABDF-TVT) based on aza-heterocycle, bis(2-oxo-7-azaindolin-3-ylidene)benzodifurandione (BABDF) as the strong acceptor, and benzodithiophene-thiophene (BDTT), bithiophene (BT), and thiophene-vinylene-thiophene (TVT) as the donor were designed and synthesized. The conjugated polymers showed significant absorption in the NIR region and a maximum absorption peak at 808 nm by adjusting the donor and acceptor units. Their photothermal properties were also investigated by using poly(ethylene glycol)-block-poly(hexyl ethylene phosphate) (mPEG-b-PHEP) to stabilize the supramolecular aggregations of conjugated polymers. Photoexcited conjugated polymer (PBABDF-TVT) nanoparticles underwent nonradiative decay when subjected to single-wavelength NIR light irradiation, leading to an excellent photothermal conversion efficiency, of 40.7%. This study provides a method to introduce strong acceptor units to design conjugated polymers with high extinction coefficients, excellent photothermal conversion efficiency, good biocompatibility, and high stability.

Luminescent liquid crystals (LLCs) have attracted significant interest in organic optoelectronic applications owing to their ordered alignment and luminescence properties. In this study, a series of dicyanodistyrylbenzene-based calamitic molecules, (2Z,2′Z)-2,2′-(1,4-phenylene)bis(3-(4-(N-alkoxy)phenyl)acrylonitrile (Cn), are reported. In addition, the mesomorphism and luminescence properties of the as-prepared Cn were evaluted. With increasing chain length to six methylene groups, Cn formed a smectic C liquid crystal phase. For C8, C12, and C18 with long flexible chains, a chiral smectic C (SmC*) phase formed because of the asymmetrical twisted configuration. The results demonstrated that the compounds are aggregation-induced enhanced emission-active materials, and the suspensions of C12 and C18 in a THF/H2O mixture exhibit green, yellow, and orange emission colors depending on the self-assembled structure, which can be modulated by controlling the aggregation speed.

Significant attention has been paid to improve the helical twisting power (β) and Δβ between the two different isomers of axially chiral azobenzene dopants in cholesteric liquid crystals (CLCs); however, the correlations between the vales (β and Δβ) with the molecular structures as well as photoisomerisation kinetics are far from clear. In this study, a series of binaphthyl-azobenzene cyclic dopants R1–R3 with different lengths of alkoxy chain was synthesised, which exhibited photochemically reversible trans–cis isomerisation in both organic solvents and liquid crystal hosts. When doping into a nematic liquid crystal, dopant R2 with one linking alkoxy group showed the highest values of β and Δβ. The results revealed that the β value was related to the dihedral angle between two naphthyl planes and the miscibility between the dopants and the host molecule. Moreover, Δβ was also depended on the photoisomerisation quantum yields. With increasing length of alkoxyl chain, the photoisomerisation rate constant of dopants increased upon ultraviolet irradiation and decreased for the reverse process upon visible light irradiation either in isotropic acetonitrile or in CLCs. These results enable the precise tuning of the pitch and selective reflection wavelength of CLCs.

Electrically responsive photonic crystals represent one of the most promising intelligent material candidates for technological applications in optoelectronics. In this research, dye-doped polymer-stabilized cholesteric liquid crystals (PSCLCs) with negative dielectric anisotropy were fabricated, and mirrorless lasing with an electrically tunable wavelength was successfully achieved. Unlike conventional liquid-crystal lasers, the proposed laser aided in tuning the emission wavelength through controlling the reflection bandwidth based on gradient pitch distribution. The principal advantage of the electrically controlled dye-doped PSCLC laser is that the electric field is applied parallel to the helical axis, which changes the pitch gradient instead of rotating the helix axis, thus keeping the heliconical structure intact during lasing. The broad tuning range (∼110 nm) of PSCLC lasers, coupled with their stable emission performance, continuous tunability, and easy fabrication, leads to its numerous potential applications in intelligent optoelectronic devices, such as sensing, medicine, and display.

The optical properties of luminescent molecules dissolved in liquid crystals have led to their proposed use in luminescent thin-film polarizers. These molecules are typically required to fulfil a range of criteria related to their absorption and emission properties, degree of alignment and stability; however, concurrently satisfying these requirements has proven a barrier in their practical use. We obtained highly polarized absorption and emission luminescent thin-film polarizer using reactive liquid crystalline monomers and highly dichroic luminescent dyes, both of which have polymerizable end groups. In situ photopolymerization of the liquid crystalline mixtures in the highly ordered SmB phase resulted in the formation of cross-linked polymeric networks in which the anisotropic absorption and emission of the film were fixed. The as-obtained product exhibited a high dichroic ratio (DR = 30) with a large fluorescence quantum yield (ϕF = 0.77). The device is both cheap and easy to fabricate and has the potential to be used in practical electro-optic applications.

In this paper, a facial method was used to fabricate polyvinyl alcohol (PVA) microlens arrays (MLAs) with controllable focal lengths on discontinuous hydrophobic surfaces. To this end, a hydrophobic materials-based solution was spin-coated onto the patterned photoresist surface. After solvent evaporation, a discontinuous hydrophobic surface was obtained by removal of the photoresist. The as-obtained microhole patterned hydrophobic layer modified substrate exhibited hydrophilic and hydrophobic properties inside and outside the microholes, respectively. The scribing of PVA solution allowed its adherence to the hydrophilic area to form a droplet self-assembly due to surface tension. PVA MLAs with radii of 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm were obtained to demonstrate the suitability of the proposed method. The curvature of MLAs can be adjusted by controlling the volume of PVA solution in the microholes or changing their sizes. In sum, the proposed PVA MLAs with high optical performances, easy fabrication, and good mechanical properties look promising for future applications in image processing, light extraction, protein detection, light-emitting diodes, sensors, and displays.

By simulating the dynamic response processes of reverse-mode polymer-stabilised cholesteric texture (PSCT) via double exponential rise/decay model, the deformation of polymer networks were quantitatively characterised. The polymer network deformation is shown to be controlled by regulating monomer concentration and the applied electric field. Increased monomer concentration facilitates the production of polymer fibrils of a higher polymer molecular weight while suppressing distortion of the polymer network. Decreased polymer network deformation assists in the decrease of the undesired hysteresis phenomenon while also demonstrating a shorter field-off response time of PSCT; however, the trade-off is increased operation voltage and decreased contrast ratio. The observed results provide useful guidelines for future PSCT material and device optimisations.

In reverse-mode polymer-stabilised cholesteric texture (PSCT), the dynamic response is derived from local director reorientation governed by dielectric coupling effect/self-assembly and polymer network deformation. A double exponential rise/decay model is proposed to investigate the underlying physical mechanisms. Through simulation of the transient rise and decay processes, the polymer network deformation in PSCT can be quantitatively evaluated. Less deformation and faster restoration speed of the polymer network can suppress hysteresis. These results provide useful guidelines for future PSCT fabrication and performance optimisation.

A highly flexible and stretchable strain sensor has been prepared by coating chemical reduction of graphene oxide on electrospun polyurethane nanofiber mats. The sensor exhibits an ohmic behavior regardless of applied strains and the current monotonically increases with the increase of the tensile strain. The morphology and stability of electrospun polyurethane nanocomposite mats were also studied. The flexible and stretchable strain sensor has great potential for practical application such as efficient human-motion detection. This cheap and simple process of graphene layer provides an effective fabrication for graphene stretchable electronic devices and strain sensors due to excellent stability and electrical proper.

Two donor–acceptor polymer semiconductors based on highly electron-deficient pyrrolo[3,4-d]pyridazine-5,7-dione unit were synthesized by Stille cross-coupling polymerization, and their thermal property, photophysical property, electrochemical property, microstructure, application as organic thin-film transistors, and photovoltaic property were investigated. Because of the strong electron-accepting characteristic of pyrrolo[3,4-d]pyridazine-5,7-dione, the new polymers (P1 and P2) exhibited much wider absorption, smaller bandgaps (1.70 vs 1.98 eV), and deeper LUMO levels (−3.60 vs −3.37 eV) than those of a phthalimide-based polymer PBDT-PhBT (Figure 1). The fabricated organic thin-film transistor devices exhibited hole-transport behavior, and the highest mobility of 1.14 × 10−3 cm2 V−1 s−1 was obtained. The bulk-heterojunction solar cells based on the two polymers as the electron donors and PC71BM as the electron acceptor showed a high open-circuit voltage and achieved a power conversion efficiency of 2.71% and 3.66% for polymers P1 and P2, respectively.

We found reversible photo/thermal isomerization of the α-cyanostilbenic derivative ( Z )-2-(4-aminophenyl)-3-(4-(dodecyloxy)phenyl)-acrylonitrile, ( Z )-CN-APHP, which is accompanied by a large decrease in compatibility when mixed with a nematic liquid crystal. Moreover, a novel optical switch using a CN-APHP doped liquid crystal that emits partially linearly polarized light is investigated. By controlling the trans–cis isomerization of CN-APHP, it is possibly to modulate not only photoluminescence intensity but also its polarization. This could open possibilities to design improved optical devices.