Intrinsically Viscoelastic Supramolecular Conjugated Polymer toward Suppressing Coffee-Ring Effect

The rational molecular design of light-emitting conjugated polymers that inherently suppress the ubiquitous coffee-ring effect(CRE)is a great challenge and the critical bottleneck for printing displays.Herein,we describe a supramolecular route to construct an intrinsically viscoelastic rigid conjugated polymer(RCP)(PHDPF-Cz)toward avoiding the CRE without sacrificing optoelectronic properties.Theπ-πstacking interactions derived fromthe pendant carbazole(Cz)units enable PHDPF-Cz to self-assemble into criss-cross nanofibers and endow its solutionwith great viscosity.Consequently,a high-quality and continuous PHDPFCz film was obtained by impeding the transport of aggregates to the droplet edge due to outward capillary flow during evaporation,in sharp contrast to the random aggregate migration and rapid precipitation generated fromthe controlled poly[4-(6-(9H-diphenylaniline-9-yl)hexyloxy)-9,9-diphenylfluorene]-co-[5-(6-(9H-diphenylaniline-9-yl)hexyloxy)-9,9-diphenylfluorene]and poly(9,9-dioctylfluorene)solutions.Finally,an efficient random laser is also achieved based on these cross-linked films with ultrastable single-chain excitonic behavior,confirming the effectiveness of our design strategy.

通过具有高表面能和延长共轭链段的耐溶剂空穴传输材料实现高效喷墨打印QLED

量子点发光二极管(QLED)溶液法制备的特点和喷墨打印高度契合,在印刷显示器领域展现出巨大的应用潜力.制作QLED器件时,下层薄膜的表面能对上层薄膜的铺展起着至关重要的作用,高表面能可以促进不同功能膜层之间的紧密接触并减少漏电流.然而,已报道的交联空穴传输材料(HTM)低的表面能不利于喷墨打印.在此,我们通过分子设计开发了一种可交联HTM及其聚合物,新的聚合物命名为[9-(4-(乙氧基甲基)苯基)-3-(7-(9-(4-(己炔基)乙氧基甲基)苯基)-9H-咔唑-3-基)-9H-芴]-9H-咔唑(PDA-FLCZ),由3,3′-(9,9-二甲基-9H-芴-2,7-二基)双[9-(4-(丙-2-炔-1-氧基)甲基)苯基]-9H-咔唑(DA-FLCZ)聚合得到.这种新型HTM采用原位光热交联和预聚后热交联两种交联策略,都可以在较低的交联温度下形成稳定的网络结构,具有优异的耐溶剂性和较高的表面能.通过优化交联工艺,交联PDA-FLCZ薄膜实现了更高的空穴迁移率和更低的陷阱密度,其对应的旋涂QLED器件的最大外量子效率(EQE)达到17.59%,比基于DA-FLCZ的器件(14.25%)高出23%.此外,基于交联PDA-FLCZ的喷墨打印QLED显示出15.28%的最大EQE,接近其旋涂器件值的90%.

In-situ-selective-UV crosslinking fabrication of solid liquid host guest electrolyte: A facile one-step method realizing highly flexible electrochromic device

Flexible electrochromic devices (FECDs) are promising candidates for the next generation of wearable electronics due to their low operating voltage and energy consumption. For the flexible electrochromic devices, the electrolyte is an important component. Typically, the electrolyte needs to be formulated according to the device structure and usage scenario. A high-performance electrolyte involves consideration of many factors, including choosing the right polymer, solvent, curing agent, and ion type to satisfy particular device specifications. In this work, a ultraviolet-curable solid–liquid host–guest (UV-SLHG) electrolyte is developed. Several aspects of performance are improved by introducing the solid–liquid coexisting microstructure without changing the electrolyte formulation, including excellent adhesion, a 30% increase in tensile characteristics, and a seven-fold increase in ionic conductivity when compared to a fully cured solid-state electrolyte. More importantly, the unique advantage of SLHG electrolytes lies that the thickness will not change significantly during bending. The FECD made by using the UV-SLHG-based electrolyte sustained 10,000 bending cycles at the bending radius of 2.5 mm while maintaining outstanding optical modulation. A wearable ring-type ECD and a battery-free FECD wine label were made as demonstrators. The UV-SLHG strategy is not only suitable for the FECDs but also universally applicable to other electrolyte-based of flexible electronics such as flexible capacitors and batteries.

Highly ordered inkjet-printed quantum-dot thin films enable efficient and stable QLEDs with EQE exceeding 23%

Inkjet-printed quantum dot light-emitting diodes(QLEDs)are emerging as a promising technology for next-generation displays.However,the progress in fabricating QLEDs using inkjet printing technique has been slower compared to spin-coated devices,particularly in terms of efficiency and stability.The key to achieving high performance QLEDs lies in creating a highly ordered and uniform inkjet-printed quantum dot(QD)thin film.In this study,we present a highly effective strategy to significantly improve the quality of inkjet-printed CdZnSe/CdZnS/ZnS QD thin films through a pressure-assisted thermal annealing(PTA)approach.Benefiting from this PTA process,a high quality QD thin film with ordered packing,low surface roughness,high photoluminescence and excellent electrical property is obtained.The mechanism behind the PTA process and its profound impact on device performance have been thoroughly investigated and understood.Consequently,a record high external quantum efficiency(EQE)of 23.08%with an impressive operational lifetime(T50)of up to 343,342h@100cdm−2,and a record EQE of 22.43%with T50 exceeding to 1,500,463h@100cdm−2 are achieved in inkjet-printed red and green CdZnSe-based QLEDs,respectively.This work highlights the PTA process as an important approach to realize highly efficient and stable inkjet-printed QLEDs,thus advancing QLED technology to practical applications.

High performance inkjet-printed QLEDs with 18.3% EQE: improving interfacial contact by novel halogen-free binary solvent system

Poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt(4,4′-(N-(4-butylphenyl))](TFB),one of the most popular and widely used hole-transport layer(HTL)materials,has been successfully applied in high performance spin-coated quantum dots-based light-emitting diodes(QLEDs)due to its suitable energy level and high mobility.However,there are still many challenging issues in inkjet-printed QLED devices when using TFB as HTL.TFB normally suffers from the interlayer mixing and erosion,and low surface energy against the good film formation.Here,a novel environment-friendly binary solvent system was established for formulating quantum dot(QD)inks,which is based on mixing halogen-free alkane solvents of decalin and n-tridecane.The optimum volume ratio for the mixture of decalin and n-tridecane was found to be 7:3,at which a stable ink jetting flow and coffee-ring free QD films could be formed.To research the influence of substrate surface on the formation of inkjet-printed QD films,TFB was annealed at different temperatures,and the optimum annealing temperature was found to enable high quality inkjet-printed QD film.Inkjet-printed red QLED was ultimately manufactured.A maximum 18.3%of external quantum efficiency(EQE)was achieved,reaching 93%of the spin-coated QLED,which is the best reported high efficiency inkjet-printed red QLEDs to date.In addition,the inkjet-printed QLED achieved similar T75 operational lifetime(27 h)as compared to the spin-coated reference QLED(28 h)at 2,000 cd·m−2.This work demonstrated that the novel orthogonal halogen-free alkane co-solvents can improve the interfacial contact and facilitate high-performance inkjet printing QLEDs with high EQE and stability.

High-resolution and large-size stretchable electrodes based on patterned silver nanowires composites

Electrodes based on composites of silver nanowires(AgNWs)and elastic polymers have been widely studied and applied in various stretchable electronic devices.However,due to the high aspect ratio of nanowires,the patterning of AgNW-based composite electrodes remains a huge challenge,especially for high-resolution complex circuit wiring on large-size elastic substrates.In this paper,we propose a method for preparing large-size stretchable circuit boards with high-resolution electrodes by the combination of screen printing and vacuum filtration of AgNWs/polydimethylsiloxane(PDMS)composite.The as-prepared stretchable electrodes have smooth edges with patterning resolution up to-50 μm.The conductivity of the composite electrode can be precisely controlled by varying deposition densities of AgNWs and have reached to 1.07 x 10^(4) S/cm when the deposition density was 2.0 mg/cm^(2).In addition,the uniformity of conductivity and the resistance-strain characteristics of composite electrodes were systematically evaluated with different AgNWs deposition densities.The composite electrodes have been successfully employed to construct a large-size programmable display system and an 18-channel surface electromyography(EMG)recording,showing great potentials for some strain-insensitive stretchable circuits in wearable and health-related electronic applications.

Highly durable machine-learned waterproof electronic glove based on low-cost thermal transfer printing for amphibious wearable applications

Gesture recording,modeling,and understanding based on a robust electronic glove(E-glove)are of great significance for efficient human-machine cooperation in harsh environments.However,such robust edge-intelligence interfaces remain challenging as existing E-gloves are limited in terms of integration,waterproofness,scalability,and interface stability between different components.Here,we report on the design,manufacturing,and application scenarios for a waterproof E-glove,which is of low cost,lightweight,and scalable for mass production,as well as environmental robustness,waterproofness,and washability.An improved neural network architecture is proposed to implement environment-adaptive learning and inference for hand gestures,which achieves an amphibious recognition accuracy of 100%in 26 categories by analyzing 2,600 hand gesture patterns.We demonstrate that the E-glove can be used for amphibious remote vehicle navigation via hand gestures,potentially opening the way for efficient human-human and human-machine cooperation in harsh environments.

Ultra-fast and low-cost fabrication of transparent paper

Transparent paper is a kind of promising and environmentally friendly material.In this study,we show that transparent paper can be fabricated in an ultra-fast and low-cost way.This low-cost top-down method only takes three steps of cell separation,lignin removal,and cold pressing to obtain a high-quality transparent paper.The fabrication time is further reduced,and the resulted transparent paper shows high transparency up to 90.3%.The application as a substrate material for transparent and flexible electronic devices is demonstrated by emulating the printed circuit on the prepared transparent paper.This top-down method will greatly promote the market-oriented applications of transparent paper as an environment friendly material.

Synthesis and red electroluminescence of a dimesityl-functionalized bistetracene

A novel dimesityl-decorated bistetracene derivative 8,16-dimesityltetraceno[2,1,12,11-opqra]tetracene（DMTA） has been synthesized and characterized. Its single crystal analysis demonstrates that the parent bistetracene backbone is almost in a plane without any intermolecular 7 r-stacking interaction. DMTA exhibited the low-energy absorption at 560/607 nm and emission spectra at 617/663 nm, respectively.The fabricated device based on DMTA doping into 2,6-bis（3-（9 H-carbazol-9-yl）phenyl）pyridine（1 %） as an emitter present a maximum brightness of 632 cd/m^2 at 14.7 V with the CIE coordinate of（0.623,0.349）.

High-performance visible-infrared broadband transparent copper mesh conductor and applications for electromagnetic shielding and heating

Transparent conductors(TCs)have widespread applications in the fields of modern photodetectors and smart windows.While TCs for visible wavelengths have seen significant advancements,the development of visible-infrared(vis-IR)broadband TCs for infrared is still a daunting challenge due to the trade-off between infrared transparency and conductivity.Here,we present a vis-IR TC fabricated by using a damage-free indirect transfer method.This method involves polymer-mediated bonding of a high-resolution,standalone copper(Cu)mesh onto infrared or visible substrates via a transfer film.The obtained Cu mesh TC exhibits excellent conductivity with a sheet resistance as low as 0.06Ω/□,as well as 81%transmittance at a visible wavelength of 550 nm and 65%transmittance at an IR wavelength of 10μm.Furthermore,a specially developed bonding strategy ensures the longterm reliability of the Cu mesh TC in harsh environments.The Cu mesh TC can be applied in both heating and electromagnetic(EM)shielding.As a transparent heater,it reaches approximately 100℃ at an applied voltage of 1.2 V within 100 s.For EM shielding,a demonstration using a stainlesssteel box with a transparent observation window which is integrated with the Cu mesh shows that while the window allows both optical and IR observations,the 4G signals(8.2 GHz)of a smartphone inside the box are effectively blocked.