Ring Fusion Elevates the Electronic Mobility of Azabenzannulated Perylene Diimide.

The backwardness of n-type organic semiconductors still exists compared with the p-type counterparts. Thus, the development of high-performance n-type organic semiconductors is of great importance for organic electronic devices and their integrated circuits. In recent years, azabenzannulated perylene diimide (PDI), as one of immense bay-region-annulated PDI derivatives, has drawn considerable attentions. However, the electronic mobilities of azabenzannulated PDI derivatives are barely satisfactory. In this contribution, the peripheral benzene ring in azabenzannulated PDI 2 was fused to the ortho position by intermolecular C-H arylation cyclization. This endows the resultant azabenzannulated PDI 4 a planar configuration as well as electron deficient pentagonal ring. As a result, the electronic mobility of 4 is almost two orders of magnitude higher than that of the nonfused azabenzannulated PDI 2. This work shall pave a new avenue in elevating the performance of azabenzannulated PDI in organic electronics.

Precise synthesis of BN embedded perylene diimide oligomers for fast-charging and long-life potassium-organic batteries.

Replacing the C[double bond, length as m-dash]C bond with an isoelectronic BN unit is an effective strategy to tune the optoelectronic properties of polycyclic aromatic hydrocarbons (PAHs). However, precise control of the BN orientations in large PAH systems is still a synthetic challenge. Herein, we demonstrate a facile approach for the synthesis of BN embedded perylene diimide (PDI) nanoribbons, and the polarization orientations of the BN unit were precisely regulated in the two PDI trimers. These BN doped PDI oligomers show great potential as organic cathodes for potassium-ion batteries (PIBs). In particular, trans-PTCDI3BN exhibits great improvement in voltage potential, reversible capacities (ca. 130 mA h g-1), superior rate performance (19 s to 69% of the maximum capacity) and ultralong cyclic stability (nearly no capacity decay over 30 000 cycles), which are among those of state-of-the-art organic-based cathodes. Our synthetic approach stands as an effective way to access large PAHs with precisely controlled BN orientations, and the BN doping strategy provides useful insight into the development of organic electrode materials for secondary batteries.

Green One-Step Strategy of Conductive Ink for Active Health Monitoring in Rehabilitation and Early Care.

Conductive ink deposited on flexible substrates through simple methods such as dyeing or printing is one of the most promising approaches for scalable fabrication of wearable electronics. However, excessive chemical additives or a complex preparation process has limited the practical applications of conductive inks. Herein, a highly stable and antibacterial AgNPs/CNT/rGO (SACR) conductive ink with the only assistance of sustainable silk sericin (SS) is developed through a green one-step strategy. SS functions as not only the reductant of silver ions and GO by donating electrons but also the dispersant and stabilizer of CNTs through strong noncovalent interactions. The universality of SACR ink is demonstrated by depositing on various flexible substrates through handwriting, screen-printing, and dyeing techniques; meanwhile, the mechanical reliability between SACR ink and substrates is validated by peeling, bending, and twisting measurements. In addition, the synergistic effects of the multilevel hierarchical 0D/1D/2D structure and abundant interfacial interactions in SACR ink are advantageous to enhancing sensing performance. An SACR ink-based strain sensor and hydrogen peroxide (H2O2) sensor are fabricated to detect physical and biochemical indicators, demonstrating the enormous potential of SACR ink in intelligent wearables for active health monitoring in early care.

Efficient Energy Transfer in a Rylene Imide-Based Heterodimer: The Role of Intramolecular Electronic Coupling.

The development of antenna molecules with simplified structures can effectively avoid the complex exciton dynamics resulting from conformational mobility. Two distinct heterodimers TP and TBP comprising a perylenediimide (PDI) donor and terrylenediimide (TDI) acting as an energy sink were investigated. Tuned by varying functionalization positions, the bay-to-bay-linked TP offers a strong chromophore coupling, while the bay-to-N-linked TBP exhibits a weak chromophore coupling. Using transient absorption spectroscopy, we found that TP underwent ultrafast vibrational relaxation (τVR < 400 fs) from upper vibrational energy levels of the singlet states after pumping at 490 nm, and followed by electron transfer (ET, τET = 2.5 ps) from TDI to PDI. TBP exhibited ultrafast excitation energy transfer (EET, τEET = 0.48 ± 0.1 ps) from the excited PDI donor to TDI acceptor, and the subsequent charge transfer (CT) process was almost quenched. This result provides insight into designing novel small molecules capable of efficient energy transfer.

Carboxylated Carbon Nanotube/Polyimide Films with Low Thermal Expansion Coefficient and Excellent Mechanical Properties.

Polyimide (PI) films with excellent heat resistance and outstanding mechanical properties have been widely researched in microelectronics and aerospace fields. However, most PI films can only be used under ordinary conditions due to their instability of dimension. The fabrication of multifunctional PI films for harsh conditions is still a challenge. Herein, flexible, low coefficient of thermal expansion (CTE) and improved mechanical properties films modified by carboxylated carbon nanotube (C-CNT) were fabricated. Acid treatment was adapted to adjust the surface characteristics by using a mixture of concentrated H2SO4/HNO3 solution to introduce carboxyl groups on the surface and improve the interfacial performance between the CNT and matrix. Moreover, different C-CNT concentrations of 0, 1, 3, 5, 7, and 9 wt.% were synthesized to use for the PI film fabrication. The results demonstrated that the 9 wt.% and 5 wt.% C-CNT/PI films possessed the lowest CTE value and the highest mechanical properties. In addition, the thermal stability of the C-CNT/PI films was improved, making them promising applications in precise and harsh environments.

Regiochemically Pure 1,6-Ditriflato-Perylene Diimide: Preparation and Transformation.

Preparation of regioisomerically pure 1,6-disubstituted perylene diimide (PDI) is not a trivial task owing to the lack of facile synthetic and separation methodologies for the precursors. Herein, we present a simple synthesis for 1,6-ditriflato-PDI (1,6-diOTf-PDI) using 1,6,9,10-tetrabromo-perylene monoimide 1 as the starting material. The selective methoxylation of 1 at the 1,6-position is the key step. Based on a four-step sequence of selective methoxylation, domino carbonylative amidation, demethylation, and triflation, 1,6-diOTf-PDI can be obtained in a satisfactory yield. Moreover, as a building block, 1,6-diOTf-PDIa can readily undergo Suzuki and Sonogashira cross-coupling reactions.

Achieving Symmetry-Breaking Charge Separation in Perylenediimide Trimers: The Effect of Bridge Resonance.

Symmetry-breaking charge separation (SB-CS) provides a very promising option to engineer a novel light conversion scheme, while it is still a challenge to realize SB-CS in a nonpolar environment. The strength of electronic coupling plays a crucial role in determining the exciton dynamics of organic semiconductors. Herein, we describe how to mediate interchromophore coupling to achieve SB-CS in a nonpolar solvent by the use of two perylenediimide (PDI)-based trimers, 1,7-tri-PDI and 1,6-tri-PDI. Although functionalization at the N-atom decreases electronic coupling between PDI units, our strategy takes advantage of "bridge resonance", in which the frontier orbital energies are nearly degenerate with those of the covalently linked PDI units, leading to enhanced interchromophore electronic coupling. Tunable electronic coupling was realized by the judicious combination of "bridge resonance" with N-functionalization. The enhanced mixing between the S1 state and CT/CS states results in direct observation of the CT band in the steady-state UV-vis absorption and negative free energy of charge separation (ΔGCS) in both chloroform and toluene for the two trimers. Using transient absorption spectroscopy, we demonstrated that photoinduced SB-CS in a nonpolar solvent is feasible. This work highlights that the use of "bridge resonance" is an effective way to control exciton dynamics of organic semiconductors.

Mechanical Behavior and Energy Dissipation of Woven and Warp-Knitted Pvc Membrane Materials under Multistage Cyclic Loading.

In order to study the mechanical behavior and energy dissipation of architectural membrane materials under multistage cyclic loading, the deformation behavior, energy dissipation, and damage characteristics of four kinds of warp-knitted and woven polyvinyl chloride (PVC) membrane materials were analyzed using multistage cyclic loading experiments. The results show that, compared with the uniaxial tensile strength, the peak values of the cyclic loading and unloading of the four material samples are lower in the warp direction but higher in the fill (weft) direction. Under multistage cyclic loading, the loading and unloading moduli of the warp knitting membrane increase with the increase in fabric density. At the same fabric density, the loading modulus and the unloading modulus are smaller than those of the warp knitting material. The total absorbed strain energy, elastic strain energy, and dissipation energy of the fill samples are higher than those of the warp samples at a low load level but lower than those at a high load level. PVC membrane materials' use strength should be controlled below a 15% stress level under long-term external force loading. In the cyclic loading process, the four PVC membrane materials are viscoelastic-plastic, so it is reasonable to define the damage variable based on the accumulation of plastic deformation.

Stretchable Supercapacitors: From Materials and Structures to Devices.

Stretchable supercapacitors have received widespread attention due to their potential applications in wearable electronics and health monitoring. Stretchable supercapacitors not only possess advantages such as high power density, long cycle life, safety, and low cost of conventional supercapacitors but also have excellent flexibility and stretchability, which make them well integrated with other wearable systems. In this review, various strategies to fabricate stretchable supercapacitors are focused. The preparation methods for stretchable electrodes/devices in the literature are carefully classified and analyzed. Three strategies for preparing stretchable electrodes/devices are summarized in detail-the design of elastic polymer substrates, stretchable electrode structures, and composite electrodes combined with elastic polymers and stretchable structures. Meanwhile, the interface problem of electrodes/devices in the stretching process is studied in depth. The research progress of multifunctional stretchable supercapacitors is also introduced. Finally, challenges and possible solutions that still need to be addressed in the future development of stretchable supercapacitors are highlighted and prospected. This review comprehensively discusses the latest research progress in the field of stretchable supercapacitors and systematically elucidates the electrochemical and mechanical properties of these devices, hoping to improve the roadmap for scientists and engineers to develop supercapacitors with high electrochemical performance and good stretchability.

New Silk Road: From Mesoscopic Reconstruction/Functionalization to Flexible Meso-Electronics/Photonics Based on Cocoon Silk Materials.

Two of the key questions to be addressed are whether and how one can turn cocoon silk into fascinating materials with different electronic and optical functions so as to fabricate the flexible devices. In this review, a comprehensive overview of the unique strategy of mesoscopic functionalization starting from silk fibroin (SF) materials to the fabrication of various meso flexible SF devices is presented. Notably, SF materials with novel and enhanced properties can be achieved by mesoscopically reconstructing the hierarchical structures of SF materials. This is based on rerouting the refolding process of SF molecules by meso-nucleation templating. As-acquired functionalized SF materials can be applied to fabricate bio-compatible/degradable flexible/implantable meso-optical/electronic devices of various types. Consequently, functionalized SF can be fabricated into optical elements, that is, nonlinear photonic and fluorescent components, and make it possible to construct silk meso-electronics with high-performance. These advances enable the applications of SF-material based devices in the areas of physical and biochemical sensing, meso-memristors, transistors, brain electrodes, and energy generation/storage, applicable to on-skin long-term monitoring of human physiological conditions, and in-body sensing, information processing, and storage.

Tuning Biradical Character to Enable High and Balanced Ambipolar Charge Transport in a Quinoidal π-System.

Herein, two bis(dicyanomethylene)-substituted quinoidal molecules QBDT and QTBDT-3H were designed and synthesized to explore the open-shell effect on tuning the charge transport behavior of organic π-functional materials. The biradical character of QTBDT-3H was confirmed by DFT calculation, variable-temperature NMR, electron spin resonance (ESR), and superconducting quantum-interfering device (SQUID). The open-shell character enables QTBDT-3H an ambipolar characteristic under ambient conditions with highly balanced electron and hole mobilities of 0.32 and 0.16 cm2 V-1 s-1, respectively.

Isomeric Effect on Optoelectronic Properties and Photovoltaic Performance of Anthraquinone-Core Perylene Diimide (PDI) and Helical PDI dimers.

Isomerism heavily influences the optoelectronic properties and self-assembly behavior of compounds and subsequently affects their device performance. Herein, two pairs of isomeric perylene diimide (PDI) dimers, PDI and PDI2, were designed and synthesized. The electron-deficient 9,10-anthraquinone group was employed as the bridge, and thus, the resultant dimers exhibited an acceptor-acceptor-acceptor (A-A-A) structure. To determine the isomeric effects on the optoelectronic properties and photovoltaic performance of these dimers, their absorptivity, luminescence, and redox behavior were studied. Bulk heterojunction organic solar cells based on these four dimers were fabricated and measured. The two PDI dimers exhibited clear differences in photovoltaic performance, whereas the two PDI2 analogues showed similar power conversion efficiencies (PCEs). The PCEs of the two PDI2 dimers are much higher than those of the PDI dimers. These results illustrate that the isomeric effect of PDI dimers is much larger than that of PDI2 dimers on the device performance, and proper expansion of conjugation could improve the device performance.

Experimental Study on Bi-Axial Mechanical Properties of Warp-knitted Meshes with and without Initial Notches.

Warp-knitted meshes have been widely used for structural reinforcement of rigid, semi-rigid, and flexible composite materials. In order to meet the performance requirements of different engineering applications, four typical warp-knitted meshes (rectangular, square, circular, and diamond) were designed and developed. The mechanical behaviors of these meshes under mono-axial and multi-axial tensile loads were compared. The influence of the initial notch length and orientation on the mechanical performance was also analyzed. The results showed that the biaxial tensile behavior of warp-knitted meshes tended to be more isotropic. The anisotropy level of the diamond warp-knitted mesh was the lowest (λ = 0.099), while the rectangular one was the highest (λ = 0.502). The notch on a significantly anisotropic mesh was propagated along the direction of larger modulus, while for a not remarkably anisotropic mesh, notch propagation was probably consistent with the initial notch orientation. The breaking strength of warp-knitted meshes with the same initial notch orientation decreased with the increase in notch length in both the wale and course directions. For warp-knitted meshes with the same initial notch length, the breaking strength in the wale direction was kept stable at different notch orientations, while that in the course direction decreased remarkably with notch orientation from 0° to 90°.

A helical perylene diimide-based acceptor for non-fullerene organic solar cells: synthesis, morphology and exciton dynamics.

Helical perylene diimide-based (hPDI) acceptors have been established as one of the most promising candidates for non-fullerene organic solar cells (OSCs). In this work, we report a novel hPDI-based molecule, hPDI2-CN2, as an electron acceptor for OSCs. Combining the hPDI2-CN2 with a low-bandgap polymeric donor (PTB7-Th), the blending film morphology exhibited high sensitivity to various treatments (such as thermal annealing and addition of solvent additives), as evidenced by atomic force microscope studies. The power conversion efficiency (PCE) was improved from 1.42% (as-cast device) to 2.76% after thermal annealing, and a PCE of 3.25% was achieved by further addition of 1,8-diiodooctane (DIO). Femtosecond transient absorption (TA) spectroscopy studies revealed that the improved thin-film morphology was highly beneficial for the charge carrier transport and collection. And a combination of fast exciton diffusion rate and the lowest recombination rate contributed to the best performance of the DIO-treated device. This result further suggests that the molecular conformation needs to be taken into account in the design of perylene diimide-based acceptors for OSCs.