Search

The realization of high-performance optoelectronic devices requires excellent charge-transporting layers and efficient carrier recombination. Herein, we synthesized cesium tungsten bronze (Cs0.32WO3) nanocrystals and utilized them as the hole-transporting material to fabricate all-inorganic perovskite light-emitting diodes (PeLEDs). Due to the excellent carrier balance characteristics via comparison between the hole-only device and electron-only device, the all-inorganic PeLEDs with CsPbBr3 as the light-emitting layer present the maximum current efficiency of 31.51 cd/A and external quantum efficiency (EQE) of 8.48%, which are self-evidently enhanced compared with the PEDOT:PSS (14.78 cd/A, 4.03%) and WO3 (24.75 cd/A, 6.18%) based devices. Considering the remarkably improved device performance, the proposed HTL of Cs0.32WO3 is promising, acting as a favorable building block for high-efficiency light-emitting devices.

Organic-inorganic halide perovskite solar cells (PSCs) still suffer from stability issues which are caused by possible erosions from moisture, ultraviolet (UV) light, heat, and so forth. An electron-transporting layer (ETL), that is, TiO2, is a key component for state-of-the-art PSCs. However, UV-caused desorption of O2- in TiO2 would accelerate the degradation of PSCs. Herein, we explored perovskite oxide, NaTaO3, for the first time as an alternative ETL in PSCs. NaTaO3 as an ETL can effectively avoid the damage from UV irradiation, inhibit the degradation of the perovskite layer, and improve the overall stability of the PSC. PSCs fabricated with NaTaO3 yielded a power conversion efficiency (PCE) of 21.07% with a retention of more than 80% of this initial PCE after 240 min UV irradiation in air while the reference device with a PCE of 20.16% can only retain about 53% of its initial PCE after the same testing condition. The developed stable perovskite oxide material of NaTaO3 provides the diversification of electron-selective contact for highly efficient and stable PSCs.

Organic heterostructures (OHSs) consist of organic micro/nanocrystals are of essential importance for the construction of integrated optoelectronics in the future. However, the scarcity of materials and the problem of phase separation still hinder the fine synthesis of OHSs. Herein, based on the α phase one-dimensional (1D) microrods and the β phase 2D microplates of one organic compound 3,3′-((1 E ,1′ E )-anthracene-9,10-diylbis(ethane-2,1-diyl))dibenzonitril ( m -B2BCB), we facilely synthesized the OHSs composed of these two polymorph phases, whose growth mechanism is attributed to the low lattice mismatch rate of 5.8% between (001) plane of α phase (trunk) and (010) crystal plane of β phase (branch). Significantly, the multiport in/output channels can be achieved in the OHSs, which demonstrates the structure-dependent optical signals with the different output channels in the OHSs. Therefore, our experiment exhibits the great prospect of polymorphism in OHSs, which could provide further applications on multifunctional organic integrated photonics circuits.

Carbon dots (CDs) that exhibit emission over the whole visible spectrum are desired for use in light-emitting diodes (LEDs). Here, CDs displaying tunable fluorescence over the whole visible region are synthesized. Different concentrations of CDs are uniformly dispersed in epoxy resin and coated on 405 nm LED chips to obtain monochrome blue, cyan, green, yellow, red, and deep red LEDs that yield a color gamut covering 99.4% of the National Television Standards Committee (NTSC) standard. These monochrome LEDs display similar high stability. Furthermore, warm and neutral white LEDs are produced by coating cyan- and red-emitting CD layers on 405 nm LED chips, achieving color-rendering indexes (CRIs) of 96.4 and 96.6, respectively. Two fluorescent conversion layers derived from one material at different concentrations simplify the preparation of high-CRI white LEDs. The uniform weak changes of the cyan and red photoluminescence peaks during operation ensure the high stability of these CD-based white LEDs. This research provides a new avenue to develop low-cost, easy-to-prepare CDs with tunable emission colors as alternative phosphors for LED-based high-performance displays and lighting.

Rationally designing and precisely constructing the dimensions, configurations and compositions of organic nanomaterials are key issues in material chemistry. Nevertheless, the precise synthesis of organic heterostructure nanomaterials remains challenging owing to the difficulty of manipulating the homogeneous/heterogeneous-nucleation process and the complex epitaxial relationships of combinations of dissimilar materials. Herein, we propose a hierarchical epitaxial-growth approach with the combination of longitudinal and horizontal epitaxial-growth modes for the design and synthesis of a variety of organic superstructure microwires with accurate spatial organisation by regulating the heterogeneous-nucleation crystallisation process. The lattice-matched longitudinal and horizontal epitaxial-growth modes are separately employed to construct the primary organic core/shell and segmented heterostructure microwires. Significantly, these primary organic core/shell and segmented microwires are further applied to construct the core/shell-segmented and segmented-core/shell type’s organic superstructure microwires through the implementation of multiple spatial epitaxial-growth modes. This strategy can be generalised to all organic microwires with tailored multiple substructures, which affords an avenue to manipulate their physical/chemical features for various applications., Rationally designing and precisely constructing the dimensions, configurations and compositions of organic micro- and nanomaterials are key issues in material chemistry, but remain challenging. Here, the authors realize the fine synthesis of organic superstructure microwires via a hierarchical epitaxial-growth approach.

Abstract Optical waveguide of organic micro/nanocrystals is one of crucial elements in miniaturized integrated photonics. One-dimensional (1D) organic crystals with various optical features have attracted increasing interests towards promising photonic devices, such as multichannel signal converter, organic field-effect optical waveguide, sensitive detector, and optical logic gate. Therefore, a summary about the 1D organic micro/nanocrystals based optical waveguide is important for the rational design and fabrication of novel optical devices towards optoelectronics applications. Herein, recent advances of optical waveguide based on 1D organic micro/nanocrystals with solid, flexible, hollow, uniformly doped, core-shell, multiblock and branched structures are summarized from the aspects of the waveguide properties and applications in photonic devices. Furthermore, we presented our personal view about the expectation of future development in 1D organic optical waveguide for the photonic applications. Graphical abstract

The rational design and the fine synthesis of organic heterostructures (OHSs) are the key steps toward integrated organic optoelectronics. Herein we have demonstrated a self-assembly approach of combining a molecular-level heterostructure with a structural-level heterostructure and regulating the noncovalent intermolecular interactions for the precise construction of OHSs: a vertical type of anthracene-TCNB heterostructure and a horizontal type of benzopyrene-TCNB heterostructure. The excellent structural compatibility and the low lattice mismatch rate of ∼5.8% between single-component microplates and cocrystal microwires allow anthracene and benzopyrene molecules to grow epitaxially on the cocrystal. Significantly, integrating the multicolor emission and the distinctive dimensional-dependent photon transportation properties of low-dimensional micro/nanostructures, the multicolor optical outputs are achieved via modulating the active/passive optical waveguides in OHSs. Our work exhibits the utilization of the multilevel heterostructure strategy, which boosts the rational design of OHSs for organic photonics.

Titanium dioxide (TiO2) is usually used as an ETL in n–i–p structure PSCs. It requires high temperature preparation, which limits commercialization of PSCs. Herein, we present a perovskite oxide SrGeO3 as a new and superior ETL which can directly replace TiO2. We synthesized SrGeO3 by a low temperature hydrothermal method and applied it as an ETL for the first time in PSCs. SrGeO3 is an excellent candidate to serve as an ETL in PSCs owing to its excellent solution processability at low temperature. SrGeO3 is about 2 times more conductive than TiO2. In addition, the energy level of the SrGeO3 thin film matches those of the other functional layers in the device, indicating the suitability of SrGeO3 as an ETL in PSCs. Finally, the power conversion efficiency (PCE) of devices prepared by using the perovskite SrGeO3 as an ETL reached 17.68% and demonstrated good stability.

The rational construction of one-dimensional (1D) nanomaterials with a hierarchical structure, including multi-block, core/shell and branching structures, is a significant challenge and a crucial step toward effective control of their electrical, optical and mechanical properties. Herein, we develop a synergistic approach, integrating precipitation and microwave processes to fabricate barnyardgrass-like CuO/Cu2O heterostructure nanowires. PEG200 is an important solvent acting as a template for the formation of the barnyardgrass-like hierarchical nanostructure as well as a reductant for subsequent reduction of CuO into Cu2O via a microwave process. Furthermore, the barnyardgrass-like CuO/Cu2O heterostructure nanowires were employed as a glucose sensor with a high sensitivity of 1281 μA mM−1 cm−2, a detection limit of 16.7 μM and good stability >20 cycles. This stepwise synergistic approach opens up a new avenue for controllably synthesizing hierarchically-structured nanomaterials with excellent performance.

Full inorganic cesium lead halide perovskites (IOPs) are regarded as attractive candidates for light-emitting diodes (LEDs) by their excellent luminescent conversion. However, unsatisfactory efficiency and stability are still the main drawbacks that hinder the commercialization progress of perovskite LEDs (PeLEDs). Here, we report an extremely uniform and flat CsPbBr3 film composing of self-assembly core–shell structured quantum dots (SCQDs) based on one-step precursor coating. The QDs size in the CsPbBr3 film is around 4.5 nm (smaller than the Bohr radius), which significantly confines injected carriers and leads to a ultrahigh exciton binding energy (Eb) of 198 meV. In addition, unfavorable surfacial defects are dramatically passivated by a thin surfacial-capping layer composed of long-chain ammonium groups (phenylalanine bromide, PPABr), resulting in an ultralow nonradiative recombination rate. Consequently, the CsPbBr3 SCQDs film presents a high photoluminescence quantum yield (PLQY) of 85%. It enable...

Anisotropic organic molecular construction and packing are crucial for the optoelectronic properties of organic crystals. Two-dimensional (2D) organic crystals with regular morphology and good photon confinement are potentially suitable for a chip-scale planar photonics system. Herein, through the bottom-up process, 2D halogen-bonded DPEpe-F4 DIB cocrystals were fabricated that exhibit an asymmetric optical waveguide with the optical-loss coefficients of RBackward =0.0346 dB μm-1 and RForward =0.0894 dB μm-1 along the [010] crystal direction, which can be attributed to the unidirectional total internal reflection caused by the anisotropic molecular packing mode. Based on this crystal direction-oriented asymmetric photon transport, these as-prepared 2D cocrystals have been demonstrated as a microscale optical logic gate with multiple input/out channels, which will offer potential applications as the 2D optical component for the integrated organic photonics.

Using a facile solution-evaporation method, we controllably fabricated DPEpe–F4DIB single-crystalline microrods and microtubes by tuning the solvent-system. Due to the thin tubular wall acting as an annular cavity, the organic microtubes demonstrated a lower optical loss of 0.0145 dB μm−1, and are promising building blocks for various optoelectronic devices.

Organic heterostructures (OHSs) integrating the intrinsic heterostructure characters as well as the organic semiconductor properties have attracted intensive attention in material chemistry. However, the precise bottom-up synthesis of OHSs is still challenging owing to the general occurrence of homogeneous-nucleation and the difficult manipulation of noncovalent interactions. Herein, we present the rational synthesis of the longitudinally/horizontally-epitaxial growth of one-dimensional OHSs including triblock and core/shell nanowires with quantitatively-manipulated microstructure via a hierarchical self-assembly method by regulating the noncovalent interactions: hydrogen bond (−15.66 kcal mol−1) > halogen bond (−4.90 kcal mol−1) > π-π interaction (−0.09 kcal mol−1). In the facet-selective epitaxial growth strategy, the lattice-matching and the surface-interface energy balance respectively facilitate the realization of triblock and core/shell heterostructures. This hierarchical self-assembly approach opens up avenues to the fine synthesis of OHSs. We foresee application possibilities in integrated optoelectronics, such as the nanoscale multiple input/out optical logic gate with high-fidelity signal., Organic heterostructures attract attention in material chemistry but the precise bottom-up synthesis is still challenging. Herein the authors present a hierarchical self-assembly approach to synthesize one-dimensional organic heterostructures by regulating the noncovalent interactions.

For practical applications of carbon dots (CDs), a major challenge is to prevent the notorious aggregation-caused quenching (ACQ) effect. Herein, a new type of CDs (CD1) has been developed that can transform from ACQ to an enhancement of fluorescence by aggregation-induced emission (AIE). The blue fluorescence of the CDs is suppressed by ACQ. However, this is accompanied by the phenomenon of AIE at a longer wavelength, resulting in the emergence and gradual enhancement of yellow fluorescence. The obtained CD1 solid powder shows a bright yellow emission with a photoluminescence quantum yield (PLQY) of 65%. The photoluminescence (PL) spectra, absorption spectra, and time-resolved PL decay curves indicate that Förster resonant energy transfer from dispersed CD1 particles to large CD1 agglomerations leads to the enhancement of yellow fluorescence. To exploit its high PLQY and strong AIE, CD1 is applied as a color-converting layer on blue light-emitting diode (LED) chips to fabricate white LEDs (WLEDs). The obtained devices show white light coordinates of (0.29, 0.38) and (0.32, 0.42), which are close to pure white light (0.33, 0.33), and luminous efficiencies of 97.8 and 93.9 lm·W

As the main performance self-evaluation index of the Kalman filter, the estimation error covariance (EEC) has been used to design the allocation cost function of task and resources for sensor tracking networks. For nonlinear systems, the sensor allocation method based on the EEC needs to adjust the allocation plans after obtaining the filtering results. Meanwhile, recent investigations have indicated that the self-evaluation function EEC of the Kalman filtering is universally inapplicable in practical applications, for which the estimation models are generally mismatched due to difficulty in accurately training parameters and approximation of nonlinear systems. Thereby, the sensors cannot be properly allocated by using the EEC as a preliminary criterion. Alternatively, observable degree (OD) is a naturally quantitative measure on observability and can be utilized to effectively measure the estimation performance. In this paper, the OD analysis with scale transform invariance for nonlinear systems is studied by using the unscented Kalman filter, the pseudostate transition matrix, and the pseudo observation matrix on the basis of the results of linear systems. Afterward, the OD of nonlinear fusion systems, the sensor utilization efficiency, the priority of tasks, and the sensor performance and sensitivity are jointly considered to formulate the optimization problem for sensor allocation. The genetic algorithm with intelligent learning function is employed to solve the optimization problem. Moreover, extensive simulation demonstrates the feasibility of the proposed approach.

Semiconductor quantum dots (QDs), traditionally based on lead or cadmium, are the promising fluorescent materials for use in bright illumination, detecting and display technology. However, the toxicity of these QDs materials traditionally based on heavy metal cause great concern to human health and environmental protection. Thus, carbon dots from pure natural materials with low toxicity and extensive resources soon raised attention. Here, we introduce a pure physical method to extract carbon dots from the seed's inner skin of torreya grandis which is a Chinese endemic plant widely grown in the southeastern China, such as in Jiangsu, Fujian and Zhejiang Provinces. These carbon dots come from natural plants and only cyclohexane and ethanol with hypotoxicity are used in extracting process to ensure the low toxicity of our material. Besides, we also fabricated light-emitting diodes based on the extracted light-emitting carbon dots. The emission peak of our devices appears at 438 nm with Commission International de I'Eclairage (CIE) color coordinate (0.177, 0.075).

Through a facile solid-state mechanochemical method, we have prepared WO3 nanobelts with a length of ∼80 nm and a width of ∼10 nm, which were doped into PEDOT:PSS as a hybrid hole-injecting layer (HIL) for conventional red quantum dot light-emitting diodes (QLEDs). The work function (WF) of the hybrid HIL was enhanced from 4.91 to 5.25 eV and the hole-injecting barrier was decreased from 0.89 to 0.55 eV. Notably, an optimal red QLED based on the hybrid HIL PEDOT:PSS:WO3 (4.0 wt%) achieved a satisfactory reduction in the driving voltage at the luminance of 100 cd A−1 from 5.18 V (pristine PEDOT:PSS) to 2.97 V. Moreover, the optimal device exhibits a maximal current efficiency of 15.5 cd A−1 and a high external quantum efficiency (EQE) of 10.60%, which are nearly two-folds higher than those (8.0 cd A−1 and 5.82%) of the reference device based on pristine PEDOT:PSS. It was demonstrated that doping these as-prepared WO3 nanobelts into the PEDOT:PSS could be an effective route toward high-performance QLEDs.

Efficient electron-injection into the emitting layer (EML) plays a pivotal role in the fabrication of high performance blue quantum dot light-emitting diodes (QLEDs). Herein, we reduce the electron-transporting barrier at the ITO/ETL (electron-transporting layer) interface from 0.7 eV to 0.4 eV by spin-coating a polyethylenimine ethoxylated (PEIE) film (8 nm) on the ITO substrate. Meanwhile, the electron-injection barrier was reduced from 0.5 to 0.1 eV at the ETL/QD interface by employing the incorporation of PEIE (0.1 wt%) into a ZnO layer. These above two interfacial modifications jointly decrease the electron barrier and make the electron transportation easier. As a result, the optimized QLEDs with the 460 nm emission peak exhibit a maximum external quantum efficiency (EQE) of 7.85%, which is enhanced by 1.4 fold compared with the reference device (5.68%). It is demonstrated that the facile interfacial modification by the organic polymer PEIE contributes to the fabrication of high-efficiency blue QLEDs.

The micro plastic forming process (MPFP) was a developing method widely used for the fabrication of miniature metallic parts. A hybrid MPFP assisted by ultrasonic vibration could be helpful to reducing forming load and improve product quality. In the ultrasonic assisted MPFP, the ultrasonic vibration was usually superimposed on the forming punch but seldom on the workpiece although the ultrasonic vibration of the workpiece could improve the micro-formability of material more effectively. This phenomenon was partly due to the weight and random shape of the workpiece. To realize the ultrasonic vibration of the workpiece in MPFP, a new type of porous block sonotrode was developed in this study. The sonotrode could convert the ultrasonic vibration from longitudinal direction to normal direction and get uniform amplitude on the central square radiant surface. It could also excite the micro workpiece or mold with resonant vibration along the normal direction and was insensitive to the fluctuation of structure and weight of micro workpiece. The simulated analysis and experiment results show that the porous block sonotrode can excite micro workpiece with ultrasonic resonant vibration, reduce the average extrusion force over 15 % and increase the extrusion height over 85 %.

Solid-state lasers (SSLs) play an important role in developing optoelectronic devices, optical communication, and modern medicine fields. As compared with inorganic SSLs, the electrically pumped organic SSLs (OSSLs) still remain unrealized because of the high lasing threshold and low carrier mobility. Herein, we first demonstrate the laser action at ∼520 nm based on the self-assembled single-crystalline organic microribbons of the aggregation-induced emission (AIE) molecules of 1,4-bis(( E)-4-(1,2,2-triphenylvinyl)styryl)-2,5-dimethoxybenzene (TPDSB). Moreover, these as-prepared organic microribbons exhibit an effective optical waveguide with a low optical loss of 0.012 dB μm-1, indicating good light confinement for laser resonator feedback. Impressively, the multiple mode and the single mode lasing are both achieved from individual organic microribbons, whose lasing threshold is as low as 653 nJ cm-2. These "bottom-up" synthesized organic microribbons based on AIE-active molecules offer a new strategy for the realization of the ultralow threshold OSSLs, which would eventually contribute to the realization of electrically pumped OSSLs.

The core/shell micro-/nanostructures with versatility, tunability, stability, dispersibility, and biocompatibility are widely applied in optics, biomedicine, catalysis, and energy. Organic micro-/nanocrystals have significant applications in miniaturized optoelectronics because of their controllable self-assembly behavior, tunable optical properties, and tailor-made molecular structure. Nevertheless, the advanced organic core/shell micro-/nanostructures, which possess multifunctionality, flexibility, and higher compatibility, are rarely demonstrated because of the dynamic nature of molecular self-assembly and the complex epitaxial relationship of material combination. Herein, we demonstrate the one-dimensional organic core/shell micro-/nanostructures with component interchange, which originates from the 4,4'-((1 E,1' E)-(2,5-dimethoxy-1,4-phenylene)bis(ethene-2,1-diyl))dipyridine (DPEpe) single-crystal microrods or the DPEpe-HCl single-crystal microrods after a reversible protonation or deprotonation process. Notably, the DPEpe/DPEpe-HCl core/shell microrods display vivid visualizations of tunable emission color via an efficient energy-transfer process during the stepwise formation of a shell layer. More significantly, these DPEpe/DPEpe-HCl and DPEpe-HCl/DPEpe core/shell microrods cooperatively demonstrate the multicolor optical waveguide properties continuously adjusted from green [CIE (0.326, 0.570)], to yellow [CIE (0.516, 0.465)], and to red [CIE (0.614, 0.374)]. Our investigation provides a new strategy to fabricate the organic core/shell micro-/nanostructures, which can eventually contribute to the advanced organic optoelectronics at the micro-/nanoscale.

Hydrology is an old discipline due to its early origination, as well as a young discipline due to its insufficient scientific foundation as a natural science. Thus hydrology has long been haunted by a debate between natural functionalities found in observations vs. model results built on many simplified assumptions. We define the hydrological maze as puzzles, paradoxes, or complexity involved in hydrologic measurements and interpretations. The objective of this study was to reveal the hydrological maze through a comprehensive review of decades of work since the 1980s on observations and experiments using a combination of natural and artificial catchments at the Chuzhou Hydrology Laboratory in China, highlighting the role of hydropedology in hillslope and catchment hydrology based on long-term monitoring of surface and subsurface flows at various soil depths and at different spatial scales. A conception has emerged that indicates the fundamental control of hydropedological factors (such as soil types, soil properties, and their spatial variations) as the trigger for the hydrological maze, including runoff generation, runoff composition, flow heterogeneity, and various hydrological puzzles. It is clear that the vadose zone is the key source for nonlinear and dissipative complexity in the hydrological maze that is intertwined with hydrochemical and hydroecological dynamics. Therein lies the hope for new hydrological insights and possible solutions to the hydrological maze.

The controlled fabrication of organic single-crystalline nanowires (OSCNWs) with a uniform diameter in the nanoscale via the bottom-up approach, which is just based on weak intermolecular interaction, is a great challenge. Herein, we utilize the synergy approach of the bottom-up and the top-down processes to fabricate OSCNWs with diameters of 120 ± 10 nm through stepwise evolution processes. Specifically, the evolution processes vary from the self-assembled organic micro-rods with a quadrangular pyramid-like end-structure bounded with {111}s and {11−1}s crystal planes to the “top-down” synthesized organic micro-rods with the flat cross-sectional {002}s plane, to the organic micro-tubes with a wall thickness of ∼115 nm, and finally to the organic nanowires. Notably, the anisotropic etching process caused by the protic solvent molecules (such as ethanol) is crucial for the evolution of the morphology throughout the whole top-down process. Therefore, our demonstration opens a new avenue for the controlled-fabrication of organic nanowires, and also contributes to the development of nanowire-based organic optoelectronics such as organic nanowire lasers.

Organic semiconductor nanowires have inherent advantages, such as amenability to low-cost, low-temperature processing, and inherent four-level energy systems, which will significantly contribute to the organic solid-state lasers (OSSLs) and miniaturized laser devices. However, the realization of near-infrared (NIR) organic nanowire lasers is always a big challenge due to the difficultly in fabrication of organic nanowires with diameters of ≈100 nm and material issues such as low photoluminescence quantum efficiency in the red-NIR region. What is more, the achievement of wavelength-tunable OSSLs has also encountered enormous challenge. This study first demonstrates the 720 nm NIR lasing with a low lasing threshold of ≈1.4 µJ cm−2 from the organic single-crystalline nanowires, which are self-assembled from small organic molecules of (E)-3-(4-(dimethylamino)-2-methoxyphenyl)-1-(1-hydroxynaphthalen-2-yl)prop-2-en-1-one through a facile solution-phase growth method. Notably, these individual nanowires' Fabry–Perot cavity can alternatively provide the red-NIR lasing action at 660 or 720 nm from the 0–1 or 0–2 radiative transition channels, and the single (660 or 720 nm)/dual-wavelength (660 and 720 nm) laser action can be achieved by modulating the length of these organic nanowires due to the intrinsic self-absorption. These easily-fabricated organic nanowires are natural laser sources, which offer considerable promise for coherent light devices integrated on the optics microchip.