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Three polymorphs of a N,S-chelated four-coordinated difluoroboron-based emitter display high contrast green (G), yellow (Y) and red (R) emissions with TADF character for the G- and R-Crystals, and RTP for the Y-Crystal, tuned by different molecular conformations and packings.

Sensing and recognizing invisible ultraviolet (UV) light is vital for exploiting advanced artificial visual perception system. However, due to the uncertainty of the natural environment, the UV signal is very hard to be detected and perceived. Here, inspired by the tetrachromatic visual system, we report a controllable UV-ultrasensitive neuromorphic vision sensor (NeuVS) that uses organic phototransistors (OPTs) as the working unit to integrate sensing, memory and processing functions. Benefiting from asymmetric molecular structure and unique UV absorption of the active layer, the as fabricated UV-ultrasensitive NeuVS can detect 370 nm UV-light with the illumination intensity as low as 31 nW cm−2, exhibiting one of the best optical figures of merit in UV-sensitive neuromorphic vision sensors. Furthermore, the NeuVS array exbibits good image sensing and memorization capability due to its ultrasensitive optical detection and large density of charge trapping states. In addition, the wavelength-selective response and multi-level optical memory properties are utilized to construct an artificial neural network for extract and identify the invisible UV information. The NeuVS array can perform static and dynamic image recognition from the original color image by filtering red, green and blue noise, and significantly improve the recognition accuracy from 46 to 90%.

Different from spiro-blocking, frontier molecular orbital engineering has been proposed to develop AT-spiro-DMACF, which shows interesting aggregation-induced delayed fluorescence (AIDF) for non-doped OLEDs.

High charge carrier mobility polymer semiconductors are always semi-crystalline. Amorphous conjugated polymers represent another kind of polymer semiconductors with different charge transporting mechanism. Here we report the first near-amorphous n-type conjugated polymer with decent electron mobility, which features a remarkably rigid, straight and planar polymer backbone. The molecular design strategy is to copolymerize two fused-ring building blocks which are both electron-accepting, centrosymmetrical and planar. The polymer is the alternating copolymer of double B←N bridged bipyridine (BNBP) unit and benzobisthiazole (BBTz) unit. It shows a decent electron mobility of 0.34 cm

The development of n-type semiconductors lags far behind that of their p-type counterparts, demonstrating the exploration of exclusive n-type π-conjugated polymers is significant. The double B←N-bridged bipyridine (BNBP)-based polymers P-BNBP-TVT containing (E)-1,2-di(thiophen-2-yl)ethene (TVT) previously reported exhibits ambipolar character because of the electron-rich nature. Herein, we incorporated strong electron-withdrawing cyano groups into the 3,3′-positions of the TVT moiety to a copolymer P-BNBP-2CNTVT to develop n-type π-conjugated polymers. The LUMO/HOMO energy levels of P-BNBP-2CNTVT are −3.80/−5.95 eV, respectively, which are ~0.4 eV lower than that of P-BNBP-TVT without cyano groups. Unsurprisingly, compared with ambipolar P-BNBP-TVT, the organic field-effect transistors (OFETs) based on P-BNBP-2CNTVT showed unipolar n-type characteristics with an electron mobility of 0.026 cm2 · V−1 · s−1 and a lower threshold voltage of ~25 V as well as high I on/I off of ~105. This study demonstrates that organoboron π-conjugated polymers could be regarded as a tool for constructing exclusive n-type semiconducting polymers used in OFETs.

Grasp estimation is a fundamental technique crucial for robot manipulation tasks. In this work, we present a scene-oriented grasp estimation scheme taking constraints of the grasp pose imposed by the environment into consideration and training on samples satisfying the constraints. We formulate valid grasps for a parallel-jaw gripper as vectors in a two-dimensional (2D) image and detect them with a fully convolutional network that simultaneously estimates the vectors’ origins and directions. The detected vectors are then converted to 6 degree-of-freedom (6-DOF) grasps with a tailored strategy. As such, the network is able to detect multiple grasp candidates from a cluttered scene in one shot using only an RGB image as input. We evaluate our approach on the GraspNet-1Billion dataset and archived comparable performance as state-of-the-art while being efficient in runtime.

π-Stacked dendrimers consisting of cofacially aligned donors and acceptors are developed by introducing three dendritic teracridan donors with orthogonal configuration and three triazine acceptors in periphery of hexaphenylbenzene skeleton. The dendritic structure and orthogonal configuration of teracridan not only make their outer acridan segments approaching to acceptor in close distance, but also fix donor and acceptor in face-to-face alignment, leading to through-space charge transfer emission with thermally activated delayed fluorescence (TADF) effect. By regulating charge transfer strength via substituent effect of acceptor, emission color of the dendrimers can be tuned from blue to yellow/red region. Solution-processed two-color white organic light-emitting diodes (OLEDs) based on blue and yellow π-stacked donor-acceptor dendrimers exhibit the maximum external quantum efficiency of 20.6 % and maximum power efficiency of 58.9 lm W-1 , representing the state-of-the-art efficiency for all-TADF white OLEDs by solution process.

Based on a donor-acceptor (D-A) structure, small molecules with thermally activated delayed fluorescence (TADF) have been widely applied in cost-effective and high-performance organic light-emitting diodes (OLEDs). As an analogue, however, D-A conjugated polymers often possess a significant frontier molecular orbital overlap because of the conjugation elongation to some degree, leading to no TADF caused by a large singlet-triplet energy splitting (∆ E ST ). To solve this problem, herein a novel steric locking strategy is proposed by incorporating methyl groups into D-A conjugated polymers. Benefitting from the methyl hindrance, the torsion between the donor and acceptor can be well tuned to form a sterically-locked conformation, so that the unwanted relaxation toward planarity and thus conjugation elongation is prevented to boost hole-electron separation. Consequently, the resultant sterically-locked D-A conjugated polymer achieves an extremely low ∆ E ST of 0.09 eV to enable efficient TADF. The corresponding doped and non-doped devices are fabricated via a solution process, revealing a record-high external quantum efficiency (EQE) of 24.0% (79.4 cd/A, 75.0 lm/W) and 15.3% (50.9 cd/A, 47.3 lm/W), respectively, together with a gentle efficiency roll-off at high luminance.

Boron (B)- and sulfur (S)-doped polycyclic aromatic hydrocarbons (PAHs) are developed as a novel kind of multiple resonance emitters for ultrapure blue thermally activated delayed fluorescence (TADF) polymers with narrowband electroluminescence. The combination of electron-deficient B atom and electron-rich S atom in PAH can form an intramolecular push-pull electronic system in a rigid aromatic framework, leading to reduced singlet-triplet energy splitting and limited structure relaxation of excited states. The critical roles of S atom in determining emission properties with respect to the oxygen analogues are in two aspects: (i) reducing energy bandgap to shift emission from human-eye-insensitive ultraviolet zone to blue region, and (ii) promoting reverse intersystem crossing process by heavy-atom effect to activate TADF effect. The resulting polymer containing B,S-doped PAH as emitter and acridan as host exhibits efficient blue electroluminescence at 458 nm with small full-width at half-maximum of 31 nm, representing the first example for ultrapure TADF polymer with narrowband electroluminescence.

Thermally activated delayed fluorescent (TADF) materials based tetracoordinate boron acceptors hold great potential for organic light emitting diode (OLED) applications; however, these emitters suffer from a low luminescent efficiency (ΦPL) and a large device efficiency roll-off. Herein, we design and synthesize two D–A-type emitters based on two fused boron ketoiminate (FBKI and aza-FBKI) acceptors and a 9,9-dimethylacridine (DMAC) donor. Through changing the carbon atom to a nitrogen atom in the fused boron ketoiminate units, a conventional fluorescent molecule (DMAC-FBKI) can be transformed into a highly efficient TADF molecule (DMAC-aza-FBKI) due to the dramatically reduced ΔEST (0.46–0.04 eV). DMAC-aza-FBKI exhibits a short delay lifetime of 2.2 μs and a large reverse intersystem crossing rate constant (kRISC ≈ 1.5 × 106 s−1), which is attributed to the rather close energy levels of its 3LE, 3CT and 1CT states based on theoretical calculations. Furthermore, compared with DMAC-FBKI (ΦPL ≈ 44%), DMAC-aza-FBKI has a higher ΦPL of 82% due to the existence of intramolecular hydrogen bonding. Consequently, the corresponding electroluminescent device achieves the highest external quantum efficiency (EQE) of 16.2% and an efficiency roll-off of only 9.3% at 1000 cd m−2, which are much better than those of the device based on the TADF-inactive DMAC-FBKI.

Organic compounds with selective near-infrared absorption and visible transparency are very desirable for fabrication of transparent/semitransparent optoelectronic devices. Herein, we develop a molecule with selective near-infrared absorption property, QBNA-O, in which four B←N units are incorporated to the core and two benzodioxin groups are introduced at the termini of the dibenzo-azaacene skeleton. QBNA-O exhibits a small optical gap of 1.39 eV due to the strong electron-donating benzodioxin groups and the strong electron-withdrawing B←N units. In toluene solution, QBNA-O shows a strong absorption peak at 856 nm with the full width at half maximum (FWHM) of only 41 nm as well as very weak absorption in the visible range from 380 nm to 760 nm. Thin films of QBNA-O exhibit the average visible transparency (AVT) of 78 % at the thickness of 205 nm and 90 % at the thickness of 45 nm. Solution-processed organic field-effect transistors (OFETs) of QBNA-O display ambipolar transporting behavior with the electron mobility of 0.52 cm2 V-1 s-1 and the hole mobility of 0.013 cm2 V-1 s-1 together with excellent air-stability. The selective NIR absorbing property and excellent charge transporting property imply that QBNA-O can be used to fabricate transparent organic optoelectronic devices.

Computer vision is a field that involves making a machine “see”. This technology uses a camera and computer instead of the human eye to identify, track and measure targets for further image processing. With the development of computer vision, such technology has been widely used in the field of agricultural automation and plays a key role in its development. This review systematically summarizes and analyzes the technologies and challenges over the past three years and explores future opportunities and prospects to form the latest reference for researchers. Through the analyses, it is found that the existing technology can help the development of agricultural automation for small field farming to achieve the advantages of low cost, high efficiency and high precision. However, there are still major challenges. First, the technology will continue to expand into new application areas in the future, and there will be more technological issues that need to be overcome. It is essential to build large-scale data sets. Second, with the rapid development of agricultural automation, the demand for professionals will continue to grow. Finally, the robust performance of related technologies in various complex environments will also face challenges. Through analysis and discussion, we believe that in the future, computer vision technology will be combined with intelligent technology such as deep learning technology, be applied to every aspect of agricultural production management based on large-scale datasets, be more widely used to solve the current agricultural problems, and better improve the economic, general and robust performance of agricultural automation systems, thus promoting the development of agricultural automation equipment and systems in a more intelligent direction. Keywords: Computer vision, Image processing, Agricultural automation, Intelligent detection

Motion planning is widely applied to industrial robots, medical robots, bionic robots, and smart vehicles. Most work environments of robots are not static, which leads to difficulties for robot motion planning. We present a dynamic Gaussian local planner (DGLP) method to solve motion planning problems in dynamic environments. In a dynamic environment, dynamic obstacles sometimes make part of the global path invalid, so the local invalid path needs to be local re-planned online. Compared with the node sampling-based methods building large-scale random trees or roadmaps, the Gaussian random path sampling (GRPS) module integrated in the DGLP directly samples smooth random paths discretized into sparse nodes to improve the local path re-planning efficiency. We also provide the path end orientation constraint (PEOC) method for the local re-planning paths in order to merge them smoothly into the global paths. In the robot experiments, the average planning time of the DGLP is 0.04s, which is at least 92.31% faster than the test methods, and its comprehensive evaluation scores, which consider the consuming time, path quality, and success rate of local re-planning, are at least 44.92% higher than the test methods. The results demonstrate that the proposed DGLP method is able to efficiently provide high-quality local re-planning paths in dynamic environments.

The copper(i) arylacetylide polymers reported previously are almost insoluble and infusible so as to restrain their applications. Herein, an unusual design strategy for stable and soluble copper(i) arylacetylide polymers is reported.

A series of blue-emitting poly(2,8-indenofluorene-co-2,7-carbazole)s, namely P(IF-Cz10), P(IF-Cz25), and P(IF-Cz50), has been designed and synthesized for use in polymer light-emitting diodes (PLEDs). With increasing carbazole content, the resultant copolymers are found to show blue-shifted emission and reduced photoluminescence quantum yields (PLQYs) in films. Consequently, P(IF-Cz25) represents the best trade-off between PLQY and blue light of these materials. The corresponding device reveals a peak external quantum efficiency of 4.12% (3.19 cd A−1, 2.78 lm W−1) and Commission Internationale de L’Eclairage coordinates of (0.150, 0.081). The results clearly indicate that the copolymerization of indenofluorene and carbazole is a promising strategy for developing blue PLEDs with simultaneous high efficiency and good color purity, with a CIEy value of

Halogen bonding, as a kind of intermolecular interaction, has rarely been used to tune solid-state emission properties of luminescent materials, especially fluorescent materials. Herein, three trans-enaminone (TE) derivatives (nonbrominated TE, monobrominated BrTE, and tribrominated Br3TE) with aggregation-induced emission property have been designed and synthesized. Two types of BrTE crystals (BrTE-B and BrTE-G) with different fluorescence properties were obtained. It was observed that their solid-state fluorescence has been enhanced by the formation of halogen bonding. In particular, the crystal BrTE-G containing Br…π interactions exhibits a fluorescence quantum yield (9.6%) nearly sevenfold higher than BrTE-B, the crystal without halogen bonding (1.4%), and fivefold higher than the nonbrominated TE derivative (2.1%). By careful inspection of the single-crystal data and theoretical calculations, the high fluorescence quantum yield of BrTE-G appears to be due to halogen-bonding interactions as well as multiple stronger intermolecular interactions which may restrain molecular motions, leading to the reduced nonradiative decay rate and the enhanced radiative decay rate. Additionally, increasing the number of bromine substituents may further promote the radiative decay rate, explaining therefore the higher fluorescence quantum yield (12.5%) of Br3TE.

The electronic properties of quinoidal compounds can be modulated both by their central quinoidal cores and by their end groups. However, there have only been a few studies of the effects of end-groups on the electronic properties of quinoidal compounds, due to synthetic challenges. In this study, we have prepared four quinoidal compounds, IDOTT, 2FIDOTT, 4FIDOTT, and 6FIDOTT, with different numbers of fluorine (F) atoms on the terminal isatin units, and the effects of terminal fluorination on their optical properties, energy levels, molecular packing (as single crystals and thin-films), and electron transport properties have been evaluated. The incorporation of F atoms decreased the HOMO/LUMO levels and blue-shifted the absorption spectra. All four quinoidal compounds showed n-type transport behavior in organic thin-film transistor (OTFT) devices, but their electron mobilities strongly depended on the number of F atoms. Among these compounds, 4FIDOTT exhibited the highest electron mobility (0.16 cm2 V−1 s−1), due to its two-dimensional electron transport, highly ordered thin-film, and appropriate morphology.

Room-temperature phosphorescence of most purely organic compounds can hardly be observed in their solutions. Here, we report a tetraphenylmethane derivative with four aldehyde groups, which exhibits clear blue phosphorescence in its solution at room temperature. Furthermore, its crystal displays a nearly 7-fold higher phosphorescence quantum yield as compared to the solution.

Four wide bandgap donor-acceptor (D-A) conjugated polymers, i.e. P-diF2T, P-TT, P-BDT and P-NDT, with bis(5-(2-decyltetradecyl)-[2,3′-bithiophen]-2′-yl)arylenes as D-units and 2-propyl-5,6-difluorobenzo[d][1,2,3]triazole (ffTAZ) as A unit were synthesized for photovoltaic applications. In P-diF2T, P-TT, P-BDT and P-NDT, 3,3′-difluoro-2,2′-bithiophene (diF2T), thieno[3,2-b]thiophene (TT), benzo[1,2-b:4,5-b']dithiophene (BDT) and naphtho[1,2-b:5,6-b']dithiophene (NDT) were used as aryl central units, respectively, to adjust the properties of the polymers. The optical bandgap is 1.83 eV for P-diF2T, 1.85 eV for P-TT, 1.90 eV for P-BDT and 2.04 eV for P-NDT. All four polymers show temperature-dependent aggregation behavior in solution, and their absorption spectra are complementary with that of non-fullerene acceptor (NFA) 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(5-hexylthiophen-2-yl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC-Th). Polymer solar cells (PSCs) based on these polymers and ITIC-Th were fabricated and characterized. Power conversion efficiencies (PCEs) higher than 7% were demonstrated for all polymers. The devices based on P-diF2T exhibited the highest PCE up to 10.08% with a high fill factor (FF) of 0.741. The good photovoltaic performance of P-diF2T is attributed to the synergies of the low-lying highest occupied molecular orbital (HOMO) energy level of the polymer and the favorable microstructures and morphology and thereby high and balanced charge carrier mobilities of the blend films. This study suggested that adjusting aromatic D units together with using alkylthiophene as side chains is an effective approach to design donor polymers for high performance PSCs based on NFA.

Organic thermoelectric materials play a vital role in flexible power generating applications, such as wearable electronics and sensor networks. While there is a wealth of research on p-type organic thermoelectric materials, developments on n-type counterparts as complementary are comparatively limited. Herein, we report a new kind of n-type small-molecule thermoelectric materials based on B←N-incorporated dibenzo-azaacenes 1,2-DBNA-2 and 1,2-DBNA-5. Because of the low-lying lowest unoccupied molecular orbital (LUMO) energy levels, 1,2-DBNA-2 and 1,2-DBNA-5 could be efficiently n-doped, and the rigid and almost planar skeleton could ensure good carrier transfer. When doped with a typical n-dopant (4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl)dimethylamine (N-DMBI), 1,2-DBNA-5 exhibits a moderate conductivity of 0.01 S cm-1 and a power factor of 0.06 μW m-1 K-2 with a Seebeck coefficient of -244.4 μV K-1 in thermoelectric devices. These results not only demonstrate that B←N-incorporated dibenzo-azaacenes are a novel class of n-type thermoelectric materials but also highlight a new strategy to develop n-type organic thermoelectric materials.

The preparation of micron- to nanometer-sized functional materials with well-defined shapes and packing is a key process to their applications. There are many ways to control the crystal growth of organic semiconductors. Adding polymer additives has been proven a robust strategy to optimize semiconductor crystal structure and the corresponding optoelectronic properties. We have found that poly(3-hexylthiophene) (P3HT) can effectively regulate the crystallization behavior of N,N′-dioctyl perylene diimide (C8PDI). In this study, we combined P3HT and polyethylene glycol (PEG) to amphiphilic block copolymers and studied the crystallization modification effect of these block copolymers. It is found that the crystallization modification effect of the block copolymers is retained and gradually enhanced with P3HT content. The length of C8PDI crystals were well controlled from 2 to 0.4 μm, and the width from 210 to 35 nm. On the other hand, due to the water solubility of PEG block, crystalline PEG-b-P3HT/C8PDI micelles in water were successfully prepared, and this water phase colloid could be stable for more than 2 weeks, which provides a new way to prepare pollution-free aqueous organic semiconductor inks for printing electronic devices.

Biomass is an important indicator for evaluating crops. The rapid, accurate and nondestructive monitoring of biomass is the key to smart agriculture and precision agriculture. Traditional detection methods are based on destructive measurements. Although satellite remote sensing, manned airborne equipment, and vehicle-mounted equipment can nondestructively collect measurements, they are limited by low accuracy, poor flexibility, and high cost. As nondestructive remote sensing equipment with high precision, high flexibility, and low-cost, unmanned aerial systems (UAS) have been widely used to monitor crop biomass. In this review, UAS platforms and sensors, biomass indices, and data analysis methods are presented. The improvements of UAS in monitoring crop biomass in recent years are introduced, and multisensor fusion, multi-index fusion, the consideration of features not directly related to monitoring biomass, the adoption of advanced algorithms and the use of low-cost sensors are reviewed to highlight the potential for monitoring crop biomass with UAS. Considering the progress made to solve this type of problem, we also suggest some directions for future research. Furthermore, it is expected that the challenge of UAS promotion will be overcome in the future, which is conducive to the realization of smart agriculture and precision agriculture.

The B←N unit has a large dipole and it is isoelectronic to C-C moiety with no dipole. Incorporating B←N units into π-conjugated system is a powerful strategy to design organic small molecules and polymers with intriguing opto-electronic properties and excellent opto-electronic device performance. However, it is unclear how the B←N unit affects electronic structures and opto-electronic properties of large π-conjugated molecules. In this work, to address this question, we developed three dibenzo-azaacene molecules in which two B←N units were introduced at different positions. Although the dibenzo-azaacene skeleton is fully π-conjugated, the effect of B←N unit on the electronic structures of the adjacent rings is much stronger than that of the distant rings. As a result, the three molecules with isomerized B←N incorporation patterns possess different electronic structures and exhibit tunable opto-electronic properties. Among the three molecules, the centrosymmetrical molecule exhibits higher LUMO/HOMO energy levels than those of the two axisymmetrical molecules. When used as the active layer in organic field-effect transistors (OFETs), while the two axisymmetrical molecules show unipolar electron transporting property, the centrosymmetrical molecule exhibits ambipolar hole and electron transporting behavior. This work not only deepens our understanding on organoboron π-conjugated molecules, but also indicates a new strategy to tune opto-electronic properties of organic semiconductors for excellent device performance.

Four conjugated molecules with thiophene-flanked diketopyrrolopyrrole (DPP) as the core and 3-(dicyanomethylidene)indan-1-one (IC), dichlorinated IC (2Cl-IC) and difluorinated IC (2F-IC) as termini, i.e.DPP1012, DPP1012-4Cl, DPP1012-4F and DPP68-4F were synthesized. These molecules have similar band gaps of ca. 1.2 eV and deep lowest unoccupied molecular orbital (LUMO) energy levels below −4.1 eV. Single crystal structure analysis showed that DPP68-4F adopted a slipped one dimensional π-stacking structure with a π–π stacking distance of 3.57 A in crystals. Top gate/bottom contact (TG/BC) organic thin film transistors (OTFTs) were fabricated via spin-coating. All molecules exhibited typical n-type characteristics with an electron mobility (μe) of up to 0.44, 0.26, 1.05 and 0.58 cm2 V−1 s−1 for DPP1012, DPP1012-4Cl, DPP1012-4F and DPP68-4F, respectively. Devices based on DPP1012-4F displayed the best device performance since its films were characterized by the highest packing order and appropriate film morphology. This work shows the great potential of the integration of the planar conjugated core and IC-type termini in designing solution processable high mobility n-type small molecule semiconductors.

In this work, two thermally activated delayed fluorescence (TADF) fluorophores (TAT-BP and TAT-2BP) based on triazatruxene (TAT) and benzophenone (BP) have been successfully prepared. While both compounds show similar green emission and typical AIE behaviors, TAT-2BP with two BP units exhibits a shorter delay fluorescence lifetime (0.54 μs) than TAT-BP with one BP unit (0.79 μs) in neat films. In solution-processable non-doped organic light-emitting diodes (OLEDs), TAT-2BP shows a better EL performance with a turn-on voltage of 2.5 V, a maximum current efficiency of 32.3 cd A−1, a maximum power efficiency of 33.0 lm W−1, and a maximum external quantum efficiency of 9.8%. Remarkably, very small efficiency roll-offs of 1.0% at 1000 cd m−2 and 2.0% at 2000 cd m−2 are realized for TAT-2BP based devices, which are also much lower than those of TAT-BP (10.9% at 1000 cd m−2 and 28.0% at 2000 cd m−2), indicating that the utilization of TAT-2BP with a shorter delay fluorescence lifetime can efficiently retard the efficiency decline.

Two isomeric 2-hexyl substituted five-ring-fused asymmetric thienoacenes, i.e., thieno[1]benzothieno[3,2-b][1]benzothiophene (BTBTT6), in which the S atom in the terminal thiophene ring is located at different positions relative to the BTBT core, were synthesized and characterized. The syn-isomer forms bilayer “head-to-head” structures with herringbone packing modes within the layers in crystals, while the anti-isomer shows “head-to-tail” single-layer structures and sandwich-herringbone packing within the layers. The difference in packing structures involved the fact that the syn-isomer has stronger intermolecular interactions than the anti-isomer. Importantly, organic thin-film transistors (OTFTs) with near-ideal transfer and output characteristics were fabricated. Mobilities in the saturation and the linear regime (μsat and μlin) of up to 11.7 and 10.6 cm2 V−1 s−1, respectively, were achieved for the syn-isomer. This is the first report on OTFTs with both μsat and μlin above 10 cm2 V−1 s−1.

Three novel water-soluble and pH neutral small molecules based on a triazatruxene (TAT) core containing sodium propanylsulfonate, sodium butanylsulfonate and sodium butanyl-2-sulfonate as the side chains, respectively, have been designed and used as hole injection materials in solution-processable organic light-emitting diodes. These molecules show a high transmittance of nearly 100% in the visible and near infrared region (400–1000 nm). Relative to PEDOT:PSS, the comparable HOMO levels and higher LUMO levels of TAT-based materials favor the efficient injection of holes to the emitting layer and the efficient blocking of electrons and excitons. Among the TAT-based materials, the device based on TAT-4C with the sodium butanylsulfonate side chains exhibits the best performance with a maximum EQE of 11.0%, a maximal current efficiency (LE) of 38.8 cd A−1 and a power efficiency (PE) of 39.2 lm W−1, which are also higher than those of the PEDOT:PSS-based device (an EQE of 10.6%, a LE of 37.6 cd A−1 and a PE of 35.1 lm W−1). In additon, all the devices based on the TAT-based molecules show better performance than PEDOT:PSS-based device at 10 000 cd m−2, owing to their wider bandgaps and higher LUMO levels than PEDOT:PSS, indicating that the utilization of these TAT-based molecules as hole injection materials retards the efficiency decline.

Seven diketopyrrolopyrrole (DPP)-based donor–acceptor (D–A) conjugated polymers, i.e., poly[2,5-bis(4-octadecyldocosyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-3,3′,4,4′-tetrafluoro-2,2′-bithiophene] (P4F2T-C40), poly[2,5-bis(4-octadecyldocosyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-1,2-bis(3,4-difluorothiophen-2-yl)ethyne] (P4FTAT-C40), poly[2,5-bis(4-octadecyldocosyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-(E)-1,2-bis(3,4-difluorothien-2-yl)ethene] (P4FTVT-C40), poly[2,5-bis(4-tetradecyloctadecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-(E)-1,2-bis(3,4-difluorothien-2-yl)ethene] (P4FTVT-C32), poly[2,5-bis(4-decyltetradecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-(E)-1,2-bis(3,4-difluorothien-2-yl)ethene] (P4FTVT-C24), poly[2,5-bis(2-decyldodecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-(E)-1,2-bis(3,4-difluorothien-2-yl)et...

Four bisisoindigo (bis-IID) derivatives containing different numbers of electron withdrawing fluorine (F) or nitrogen (N) atoms and eight alternating copolymers of them with 2,2′-bithophene (BT) or 3,3′,4,4′-tetrafluoro-2,2′-bithiophene (4FBT) were synthesized. Depending on the numbers of F and N atoms incorporated, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels of the polymers were feasibly tuned in the ranges of −5.51 to −6.06 eV and −3.64 to −4.01 eV, respectively. Top gate and bottom contact (TGBC) organic thin-film transistors (OTFTs) were fabricated to study the semiconducting properties of the polymers. Five polymers, i.e., P0F-BT, P2F-BT, P4F-BT, P2N2F-BT, and P0F-4FBT that contain 0–4 F and N atoms in the repeating unit, with HOMO and LUMO energy levels above −5.90 and −3.80 eV, respectively, all showed ambipolar OTFT characteristics. Three other polymers P2F-4FBT, P4F-4FBT, and P2N2F-4FBT that contain 6 or 8 F and N atoms with HOMO ...

We herein report the synthesis and characterization of four asymmetric conjugated oligomers based on polycyclic aromatics, i.e. , 2-(5-hexylselenophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene (BTBT-S6), 2-(5-hexylfuryl-2-yl)[1]benzothieno[3,2-b][1]benzothiophene (BTBT-F6), 2-(5-hexylselenophen-2-yl)[1]benzoselenopheno[3,2-b][1]benzoselenophene (BSBS-S6) and 2-(5-hexylfuryl-2-yl)[1]benzofuro[3,2-b][1]benzofuran (BFBF-F6), for elucidating the influence of chalcogens on molecular geometries, electronic structures, thin film microstructures and the performance of organic thin-film transistors (OTFTs). Compared to the previously reported analogue 2-(5-hexylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene (BTBT-T6), all four molecules have higher-lying highest occupied molecular orbital (HOMO) energy levels. BTBT-S6 and BSBS-S6 (S replaced by Se atoms) display similar mesomorphic behavior and packing motif in solid state. However, BSBS-S6 shows much poorer crystallinity. Only crystal phase was observed for BTBT-F6 and BFBF-F6 (S replaced by O atoms). These two molecules also adopt the molecular arrangements, film growth modes and film morphology distinct from BTBT-S6 and BSBS-S6. Thus, the four molecules exhibited very different OTFT performance. BTBT-S6 showed the highest mobility of 4.68 cm 2 V −1 s −1 and all other three compounds exhibited mobilites lower than 1 cm 2 V −1 s −1 .

Two polythiophenes with carboxylate side chains and vinylene linkers in conjugated backbones, i.e., poly[5,5′-(E)-bis(2-hexyldecyl)-2,2′-(ethene-1,2-diyl)bis(thiophene-3-carboxylate)-alt-5,5′- 2,2′-bithiophene] (PBT) and poly[5,5′-(E)-bis(2-hexyldecyl)-2,2′-(ethene-1,2-diyl) bis(thiophene-3-carboxylate)-alt-5,5′-thieno[3,2-b]thiophene] (PTT), were synthesized and characterized. Compared to poly(3-hexylthiophene) (P3HT), both polymers displayed deeper HOMO energy levels caused by the introduction of the electron-withdrawing carboxylate group and lower band gaps and shorter π-π stacking distances (ca. 3.5 A) due to the incorporation of vinylene linkers in the conjugated backbones. Polymer PBT possesses greater self-organization ability and thereby more ordered intermolecular packing in solid state. Consequently, organic field-effect transistors (OFETs) based on PBT showed a hole mobility of 0.24 cm2 V−1s−1, much higher than that (0.073 cm2 V−1s−1) of PTT. Polymer solar cells (PSCs) with the two polymers as donor materials and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as acceptor material were fabricated, and both PBT- and PTT-based PSCs showed open circuit voltage (Voc) above 0.8 V. Owing to the better hole transport property and more ordered nano-fibrillar film morphology, PBT-based PSCs exhibited a superior photovoltaic performance with power conversion efficiency (PCE) of 6.25%, higher than that of PTT-based PSCs (PCE = 5.53%). This study indicates that simultaneously introducing electron-withdrawing carboxylate in side chains and vinylene linkers in conjugated backbones could efficiently tune the energy levels and enhance the π-π interactions between conjugated backbones.

We disclose a novel strategy to design n-type acenes through the introduction of boron-nitrogen coordination bonds (B←N). We synthesized two azaacenes composed of two B←N units and six/eight linearly annelated rings. The B←N unit significantly perturbed the electronic structures of the azaacenes: Unique LUMOs delocalized over the entire acene skeletons and decreased aromaticity of the B←N-adjacent rings. Most importantly, these B←N-containing azaacenes exhibited low-lying LUMO energy levels and high electron affinities, thus leading to n-type character. The solution-processed organic field-effect transistor based on one such azaacene exhibited unipolar n-type characteristics with an electron mobility of 0.21 cm2 V-1 s-1 .

Flexible H2S sensors were fabricated based on ultrathin dinaphtho [3, 4-d:3’, 4’-d’] benzo [1, 2-b:4, 5b’] dithiophene (Ph5T2) single-crystal organic field-effect transistors, and response performances at different deformation states were investigated. The flexible devices exhibited strikingly different sensing behaviors under different deformation states toward H2S at room temperature. In a tensile state with ${r} = \textsf {7}$ mm, the flexible sensor presented an unprecedented response as high as 400% at 1 ppm H2S, which is almost one order of magnitude higher than the response in a flat state and surpasses all reported flexible H2S sensors. Such a surprising improvement provides an effective way to enhance the response of gas sensors and shows the potential advantage of using flexible sensors in tensile states.