Non-fullerene fused-ring electron acceptors boost the power conversion efficiency of organic solar cells, but they suffer from high synthetic cost and low yield. Here, we show a series of low-cost ...noncovalently fused-ring electron acceptors, which consist of a ladder-like core locked by noncovalent sulfur-oxygen interactions and flanked by two dicyanoindanone electron-withdrawing groups. Compared with that of similar but unfused acceptor, the presence of ladder-like structure markedly broadens the absorption to the near-infrared region. In addition, the use of intramolecular noncovalent interactions avoids the tedious synthesis of covalently fused-ring structures and markedly lowers the synthetic cost. The optimized solar cells displayed an outstanding efficiency of 13.24%. More importantly, solar cells based on these acceptors demonstrate very low non-radiative energy losses. This research demonstrates that low-cost noncovalently fused-ring electron acceptors are promising to achieve high-efficiency organic solar cells.
Single pure organic molecular white light emitters (SPOMWLEs) are of significance as a new class of material for white lighting applications; however, few of them are able to emit white ...electroluminescence from organic light-emitting diodes. Herein, donor−π–acceptor conjugated emitters, 2PQ–PTZ and 4PQ–PTZ, were designed and synthesized as SPOMWLEs for white light emission considering the distinct advantages of their conformation isomers. The coexistence of conformational isomers in 2PQ–PTZ, which is the first experimental evidence of the coexisting quasi-axial and quasi-equatorial conformers, provides ideal flexibility to obtain white light emission from their simultaneous and well-separated fluorescence and thermally activated delayed fluorescence. With these remarkable properties, a 2PQ–PTZ-based white light-emitting diode (LED) with a CIE of (0.32, 0.34) and color rendering index (CRI) of 89 is demonstrated. Further, the white organic light-emitting diode (OLED) of 2PQ–PTZ exhibits a high external quantum efficiency (EQE) of 10.1%, which is the reported highest performance among SPOMWLE-based OLEDs.
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IJS, KILJ, NUK, PNG, UL, UM
We designed and synthesized three PDI derivatives ( PDI-II , PDI-III and PDI-IV ). All these acceptor molecules have a central benzene core and the PDI units are linked to the central benzene core by ...an acetylene spacer. PDI-II is a linear molecule, which bears two flanked PDI units, PDI-III is a c 3 -symmetrical star-shaped molecule with three peripheral PDI units, and PDI-IV is a star-shaped molecule with four PDI units linked to the 1,2,4,5-positions of the central benzene core. These absorption features indicated that the PDI units in PDI-II and PDI-III are planar, whereas the PDI units in PDI-IV are twisted due to the steric crowding. Compared with the linear PDI-II , the star-shape could effectively prevent PDI-III and PDI-IV from forming large aggregates when blended with the donor polymer PBDB-T. PBDB-T: PDI-II , PBDB-T: PDI-III and PBDB-T: PDI-IV based OSCs gave power conversion efficiencies (PCEs) of 3.05%, 6.00% and 1.04%, respectively. The big differences in electron mobility and PCE for PDI-III and PDI-IV are probably due to the fact that the PDI units in PDI-III are planar and those in PDI-IV are twisted.
With cyclooctatetrathiophene (COTh) as building block, two α,α,α,α-tetraaryl COThs, COThP and COThTh have been efficiently synthesized. Phenyl and thienyl were employed as end-capping groups to ...introduce to COTh and increase its conjugation. For enlarging the special ‘saddle’ shaped structure, a pentamer of COTh was synthesized via Negishi reaction and CuCl2-promoted oxidative coupling reaction. The pentamer (COThF) is a new type of dendrimer with COTh as dendron, which presents an artistic configuration possessing a large saddle shape. All compounds were fully characterized by 1H NMR, 13C NMR, HRMS and IR. The crystal structures of COThP and COThTh were confirmed by X-ray analysis. The molecular configuration of COThF was optimized by theoretical calculations. Their UV–vis properties, electrochemical behaviours and thermo-gravimetric analysis of COThP, COThTh and COThF were also described.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Fault diagnosis and classification (FDC) is an important part of prognostics and health management for ensuring safety and performance in the flight. However, it is challenging to achieve accurate ...FDC only based on single senor readings. In this paper, a fused FDC model among multiple different sensors is stabled by a hybrid deep learning architecture combining a sparse autoencoder (SAE) and a convolutional neural network (CNN). The hybrid model uses the SAE to enhance the hidden fault signal features in the multiple sensor signals, and then classifies the obtained feature map using the CNN. This method, which combines the advantages of the SAE in feature extraction and of the CNN in local feature recognition, fully utilizes the spatiotemporal coupling characteristics of multi-sensor signals. The FDC accuracy obtained by the proposed method when applied to a flight test data set is 93.78%, compared with 66.67% obtained using the combined SAE and feedforward neural network method and 83.11% obtained using the CNN only.
Two novel helicene-like molecules based on naphthotetrathiophene are successfully synthesized. All target molecules and intermediates are characterized by 1H NMR, 13C NMR, IR, and HRMS. Their ...electrochemical and photophysical properties are studied. The configurations of the molecules are optimized by DFT quantum calculations and UV–vis behaviors are also predicted to further understand the origin of different absorption bands. We believe the current work illustrated an efficient way for the design and synthesis of sophisticated structures with naphthotetrathiophene as building blocks.
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IJS, KILJ, NUK, PNG, UL, UM
Nonfullerene acceptors (NFAs), which usually possess symmetric skeletons, have drawn great attention in recent years due to their pronounced advantages over the fullerene counterparts. Moreover, ...breaking the symmetry of NFAs could fine tune the molecular dipole, solubility, energy level, intermolecular interaction, molecular packing, crystallinity, etc., and give rise to improved photovoltaic performance. Currently, there are three main strategies for the design of asymmetric NFAs. This review highlights the recent advances of high-performance asymmetric NFAs and briefly outlooks the materials exploration for the future.
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Asymmetric NFAs could fine tune the molecular characteristics such as dipole moments, solubility, molecular packing, crystallinity etc., and give rise to further enhancements of the photovoltaic performances. This review briefly highlights the recent advances of high-performance asymmetric A-D-A and A-DA'D-A acceptors and outlooks the future direction for material exploration.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Ligand free copper-catalyzed hydroacylation reaction of aldehydes with azodicarboxylates was carried out in good to excellent yields under mild conditions. Especially, aromatic aldehydes were good ...substrates for this reaction. The method is simple, economical, and has practical advantages for the construction of carbon–nitrogen bonds.
The hydroacylation reaction of aldehydes with azodicarboxylates catalyzed by copper(II) acetate monohydrate has been reported. The reaction of various aldehydes gave the corresponding hydroacylation products in 60–98% yields under mild conditions. The method is simple, economical, and has practical advantages for the construction of the carbon–nitrogen bonds.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Four cross-conjugated butterfly-shaped molecules were designed and synthesized with the branched tetrakis(thiophene-2-yl)ethene or the planar naphthotetrathiophene as the donors and dicyanovinylene ...as the acceptor. Owing to the donor–acceptor conjugated structures, these molecules exhibited broad and strong absorbance in the UV–vis region. Their electrochemical and photophysical properties were studied; in addition, the UV–vis behaviors were also described by virtue of DFT calculations to further understand the origins of different absorption bands and efficient charge transfer was observed for given optical transitions from the ground states to the excited states in natural transition orbitals. Finally, these butterfly-shaped molecules were applied to fabricate organic photovoltaic devices and we believe the current work illustrated an efficient way for the design and synthesis of sophisticated structures with the tetrathiophene building blocks.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Heat and mass transfer between porous media and fluid is a complex coupling process, which is widely used in various fields of engineering applications, especially for natural and artificial ...fractures in oil and gas extraction. In this study, a new method is proposed to deal with the flow and heat transfer problem of steady flow in a frac- ture. The fluid flow in a fracture was described using the same method as Mohais, who considered a fracture as a channel with porous wall, and the perturbation method was used to solve the mathematical model. Unlike pre- vious studies, the shear jump boundary condition proposed by Ochoa-Tapia and Whitaker was used at the inter- face between the fluid and porous media. The main methods were perturbation analysis and the application of shear jump boundary conditions. The influence of permeability, channel width, shear jump degree and effective dynamic viscosity on the flow and heat transfer in the channel was studied by analysing the analytical solution. The distribution of axial velocity in the channel with the change of the typical parameters and the sensitivity of the heat transfer was obtained.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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