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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.

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

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.