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Host material with appropriate thermal stability and solubility is essential for inkjet printing (IJP) organic light-emitting diodes (OLEDs).Herein, three new host materials with different molecular symmetries have been designed for IJP OLEDs.

It is a great challenge for the rational molecular design of light-emitting conjugated polymers to inherently suppress the ubiquitous coffee-ring effect (CRE), which is the critical bottleneck for ...

Polymeric hole-transport materials (HTMs) have been widely used in quantum-dot light-emitting diodes (QLEDs). However, their solution processability normally causes interlayer erosion and unstable film state, leading to undesired device performance. Besides, the imbalance of hole and electron transport in QLEDs also damages the device interfaces. In this study, we designed a bis-diazo compound, X1, as carbene cross-linker for polymeric HTM. Irradiated by ultraviolet and heating, a poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt(4,4'-(

Textile-based electronics hold great promise because they can endow wearable devices with soft and comfortable characteristics. However, the inherent porosity and fluffiness of fabrics result in high surface roughness, which presents great challenges in the manufacture of high-performance fabric electrodes. In this work, we propose a thermal transfer printing method to address the above challenges, in which electrodes or circuits of silver flake/thermoplastic polyurethane (TPU) composites are prefabricated on a release film by coating and laser engraving and then laminated by hot-pressing to a variety of fabrics and textiles. This universal and scalable production technique enables fabric electrodes to be made without compromising the original wearability, washability, and stretchability of textiles. The prepared fabric electrodes exhibit high conductivity (5.48 × 10

Three AIEE-active V-shaped fused-biscoumarin derivatives were prepared and their potential for application in OLED was explored.

Two coumarin-triarylimidazole hybrid derivatives having a N,N-diethylamine at 7-position and triaryl-substituted imidazole at 3-position on the coumarin core, 3-(1-(4-(tert-butyl)phenyl)-4,5-diphenyl-1H-imidazol-2-yl)-7-(diethylamino)-2H-chromen-2-one (C-IM-Bu) and 3-(1-(4-cyanophenyl)-4,5-diphenyl-1H-imidazol-2-yl)-7-(diethylamino)-2H-chromen-2-one (C-IM-CN), were successfully synthesized for application in organic-light emitting. Their photophysical and electrochemical properties, thermal stability and electroluminescent properties were investigated. The results showed that these compounds have excellent thermal stability, and exhibit strong blue-green emission in dichloromethane solution and green emission in thin solid films. Further, the solution-processed doped devices based on the compounds were fabricated, in which the devices fabricated from C-IM-CN exhibited the best device performance with a turn-on voltage of 3.6 V, a maximum brightness of 6896 cd/m2, a maximum current efficiency of 6.39 cd/A and a maximum external quantum efficiency of 2.92%.

Manufacturing cost is a major concern for electrochromic device (ECD) applications in smart windows for energy saving and low-carbon economy. Fully printing instead of a vacuum-based chemical vapor deposition (CVD) process is favored for large-scale fabrication of ECDs. To adapt to the screen printing process, a UV curable solid-state electrolyte based on lithium bis(trifluoromethane-sulfonyl) imide (LiTFSI) was specially formulated. It contains poly(ethylene glycol) diacrylate (PEG-DA), LiTFSI, water, and ethyl acetate. The optimized ECDs have achieved a 0.6 s bleaching time at 0.6 V and a 1.4 s coloring time at -0.5 V. The ECDs also exhibited excellent stability, which could endure 100 000 cycles of color switching while still maintaining 35% of transmittance change at a 550 nm wavelength. A demo ECD has been fabricated with a screen printed electrolyte, exhibiting stable switching between the clear state and patterned color state.

Wearable display has attracted more and more attention from academia and industry due to its potential applications in entertainment and fashion, human–computer interaction, intelligent clothing, a...

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.

Three 2,7,12-trisubstituted triazatruxene derivatives containing different imidazole derived moieties, 5,10,15-tributyl-2,7,12-tris(4-(1-(4-(tert-butyl)phenyl)-1H-phenanthro[9,10-d] imidazol-2-yl)phenyl)-10,15-dihydro-5H-diindolo[3,2-a:3′,2′-c]carbazole (2,7,12-TPI-TAT), 5,10,15-tributyl-2,7,12-tris(4-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)-10,15-dihydro-5H-diindolo[3,2-a:3′,2′-c]carbazole (2,7,12-TBI-TAT) and 5,10,15-tributyl-2,7,12-tris(4-(1-(4-(tert-butyl)phenyl)-4,5-diphenyl-1H-imidazol-2-yl)phenyl)-10,15-dihydro-5H-diindolo[3,2-a:3′,2′-c]carbazole (2,7,12-TIM-TAT), were synthesized by grafting different imidazole derived moieties with different electron-withdrawing abilities onto the 2-, 7- and 12-positions of a triazatruxene (TAT) core. A combination of thermal, photophysical and electrochemical characterization studies of these compounds was conducted to investigate the influence of different imidazole derived moieties on the optoelectronic properties of the compounds. Furthermore, solution-processed doped and nondoped devices based on the compounds were fabricated, in which the doped device of 2,7,12-TPI-TAT exhibited the best device performances, while the nondoped device of 2,7,12-TBI-TAT showed the best device performances.

Two 2,7-disubstituted spiro[fluorene-9,9′-xanthene] derivatives, 2,7-bis(4-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)spiro[fluorene-9,9′-xanthene] (SFX-2BI) and 2,7-bis(4-(1-(4-(tert-butyl)phenyl)-4,5-diphenyl-1H-imidazol-2-yl)phenyl)spiro[fluorene-9,9′-xanthene] (SFX-2IM), were synthesized by grafting imidazole-derived moieties with different electron-withdrawing abilities onto the 2- and 7-positions of a spiro[fluorene-9,9′-xanthene] (SFX) core. Their photophysical and electrochemical properties, thermal stability and electroluminescent properties were investigated. The results showed that these compounds have excellent thermal stability and exhibit strong deep-blue emission in dichloromethane solution. In addition, the vacuum-processed doped and non-doped devices based on SFX-2BI and SFX-2IM were fabricated, in which the device prepared using SFX-2BI as the emitting material exhibited the best device performance with a turn-on voltage of 5.5 V, a maximum brightness of 3984 cd m−2, a maximum current efficiency of 3.65 cd A−1 and a maximum external quantum efficiency of 2.61%.

Two cross-linkable iridium(III) complexes, Ir(L)2(acac) and Ir(L)2(Stpip), where L = 1-phenyl-2-(4′-vinyl-[1,1′-biphenyl]-4-yl)-1H-benzo[d]imidazole, acac = acetylacetonate, and Stpip = bis(diphenylphorothioyl)amide, were synthesized and characterized by elemental analysis, NMR (1H and 13C) spectroscopy and HRMS. The iridium(III) complexes exhibited excellent thermal stability and green–yellow emission with a maximum main peak at 563 nm. The photoluminescence quantum yields of Ir(L)2(acac) and Ir(L)2(Stpip) were 2.77% and 1.80%, respectively, in CH2Cl2 solution. The vacuum-processed electroluminescence device fabricated from Ir(L)2(acac) at 4 wt% doping concentration exhibited a maximum current efficiency (CEmax) of 26.3 cd A−1, a maximum brightness of 9645 cd m−2 and a maximum external quantum efficiency (EQEmax) of 14.7%. The solution-processed electroluminescence device based on Ir(L)2(acac) exhibited a maximum current efficiency (CEmax) of 3.71 cd A−1, a maximum brightness of 2237 cd m−2 and a maximum external quantum efficiency (EQEmax) of 1.36%.

Efficient approach based on the photochemistry of benzophenone has been developed for the cross-linking of the polymer hole-transporting layer (HTL). The cross-linked poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(4,4'-(N-(4-butylphenyl) (TFB) thin films showed high solvent stability, smooth surface morphology, and improved charge-carrier mobility. The solution-processed red, green, and blue (RGB) quantum dot light-emitting diodes (QLEDs) based on the cross-linked HTLs showed much better performances than the corresponding devices based on the pristine TFB HTLs. The spin-coated red QLEDs based on the cross-linked HTLs showed the maximum current efficiency (CE), the maximum power efficiency (PE), and the peak external quantum efficiency (EQE) of 32.3 cd A-1, 42.3 lm W-1, and 21.4%, respectively. The inkjet-printed red QLEDs with the cross-linked HTLs exhibited the CE, PE, and EQE of 26.5 cd A-1, 37.8 lm W-1, and 18.1%, respectively. The high-performance HTLs were obtained by significantly reducing the amount of cross-linking agents.

The patterning of silver nanowires (AgNWs) is subject to critical challenges, which have seriously limited their practical applications. This work describes a simple and efficient method combining screen printing with vacuum filtration for patterning AgNW networks. The screen-printed poly(dimethylsiloxane) (PDMS) mask layer was shown to be strongly adhered to the filtration membrane, which resulted in well-defined sharp edges of the deposited AgNW patterns, and a 50 μm patterning resolution was achieved. The patterned films with low densities of AgNWs (≤15 μg/cm2) were transferred to the surface of PDMS to make patterned stretchable transparent conductive films (TCFs). The low sheet resistance of 7.3 Ω/sq was achieved at an optical transmittance of 79.6% (at 550 nm wavelength) with a AgNW deposition density of only 12.5 μg/cm2. As an application example, the patterned TCFs were used as the top electrodes to fabricate stretchable alternating current electroluminescent (ACEL) displays with stretchability up to 70% of their original dimension, which were applied to a smart system for simulating heart beats together with a digitally operated flexible circuit. The ACEL device exhibited a bright and uniform emission with a clear and smooth edge even with a pattern width as narrow as 100 μm, as well as exceptional elasticity and durability in spite of bending, stretching, and twisting. The present work provides a new way of patterning AgNWs and can be extended to a variety of applications.

Poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt(4,4′-(N-(4-butylphenyl)))] (TFB) has been widely used as a hole transport layer (HTL) material in cadmium-based quantum dot light-emitting diodes (QLEDs) be...

Three biscoumarin dyes bridged by polycyclic aromatic bridges (anthracen, pyrene and dibenzo[g,p]chrysene) were prepared as the emissive materials for the application of organic light-emitting devices. The relationship between their structures, photophysical properties, electrochemical properties and performances of organic light-emitting devices are described. The multilayered doped devices with a configuration of ITO/NPB (20 nm)/TBADN: biscoumarin compound (x wt%, 30 nm)/TPBi (30 nm)/Liq (2 nm)/Al (100 nm) have been successfully fabricated by vacuum-deposition method. All the devices showed green emission with high electroluminescent efficiencies. Especially, the device based on the compound containing pyrene as a bridge group at 7% doping concentration showed the best performance with a maximum brightness of 10552 cd/m2, maximum luminous efficiency of 5.39 cd/A and maximum external quantum efficiency (EQE) of 2.35%. Keywords: Biscoumarin derivative, Polycyclic aromatic bridge, Dibenzo[g,p]chrysene, Photoluminescence, Electroluminescence

Cross-linking strategies of hole transport materials (HTMs) have been widely investigated and used in various optoelectronic devices, mainly owing to their excellent solvent resistance and thermal stability. More importantly, the energy level and charge mobility of cross-linkable HTMs can be fine-tuned through precise molecular design, which offers great opportunities to explore and screen efficient HTMs. Currently, the investigations of cross-linkable HTMs are limited in the research of quantum dot light emitting diodes (QLEDs), which could not realize the full advantages of the superior emissive properties of QDs and benefits of solution-processing fabrication techniques. Thus, we synthesized two cross-linkable materials DV-SFCZ and DV-FLCZ with different center cores to explore the influence of the central steric hindrance on the properties. With a smaller central steric hindrance, the cross-linking temperature of DV-FLCZ is 75 °C lower than that of DV-SFCZ, and the cross-linking time is shortened by 2/3 times, which is of great significance in future practical application. DV-FLCZ shows a better hole transport property, which favors hole injection into the QD layer. Notably, red, green and blue QLEDs with DV-FLCZ as the HTM achieved a maximum EQE of 20.5%, 16.6% and 8.5%, respectively, which are much better than the devices based on DV-SFCZ as the HTM. To the best of our knowledge, the results represent the highest EQE values of QLED performance using cross-linkable materials alone as hole transport layers.

Stretchable electrodes have attracted great attention for developing next generation wearable and flexible electronics. However, the fabrication of stretchable electrodes with high electrical stability, especially high omnidirectional stretchability, remains challenging. Here, we proposed a scheme for making stretchable electrodes based on wrinkled silver nanowires (Ag NWs) through the shrinkage of electrospun polymer fibers. The Ag NWs were vacuum filtered on electrospun fluoroelastomer fiber mats, and then they formed isotropic wrinkles on the scale of several micrometers after the thermal induced shrinkage of the fibers. An ∼80% areal shrinkage was achieved in the composite fiber mat under the conditions of 7 kV applied voltage during electrospinning and 120 °C thermal treatment temperature. The co-shrunk Ag NW electrodes reached high stretchability of up to 500%. The resistance increased only by a factor of ∼0.65 under 100% strain and ∼0.1 under 50% strain. These random wrinkles endow the electrodes with high omnidirectional stretchability, no significant variation of resistance change was observed along the hexagonal stretched directions at ∼80% strain. In addition, the stretchable electrodes demonstrated good electrical stability, with only

Here we demonstrate a novel SERS-active substrate assembled by silver nanowire (Ag NW)-embedded porous polystyrene (PS) fibers. Ag NWs are synthesized through a glycerol-mediated solvothermal method firstly, then electrospun into PS porous fibers. The as-synthesized Ag NWs are embedded in PS fiber and aligned orderly along the axial direction. Porous structure appears in PS fiber due to the phase separation induced by rapid evaporation of solvents. Large amounts of holes not only greatly improve the sample collection efficiency of the SERS-active substrate, but also significantly facilitate the adsorption of target molecules on the surface of Ag NWs, thus increasing the probability of enhancement of target molecules. In addition, compared with polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP), PS has better solvent resistance. The detection limit of 4-aminothiophenol (4-ATP) on our fabricated electrospun fiber mats is 10−7 M, and the electrospun fiber mats showed good reproducibility of SERS signal detection. This study proposes a feasible strategy for the large-scale preparation of flexible SERS-active substrate assembled by Ag NW-embedded porous PS fibers. The produced flexible SERS substrates may have potential application in wearable sensors for the trace detection of chemical and biological molecules.

Printed metal nanogrid electrode exhibits superior characteristics for use in flexible organic solar cells (OSCs). However, the high surface roughness and inhomogeneity between grid and blank region is adverse for performance improvement. In this work, a thin amorphous indium tin oxide (ITO) film (α-ITO) is introduced to fill the blank and to improve the charge transporting. The introduction of α-ITO significantly improves the comprehensive properties of metal grid electrode, which exhibits excellent bending resistance and long-term stability under double 85 condition (under 85 °C and 85% relative humidity) for 200 h. Both experimental and simulation results reveal α-ITO with a sheet resistance of 20 000 Ω □

Toward next-generation electroluminescent quantum dot (QD) displays, inkjet printing technique has been convinced as one of the most promising low-cost and large-scale manufacturing of patterned quantum dot light-emitting diodes (QLEDs). The development of high-quality and stable QD inks is a key step to push this technology toward practical applications. Herein, a universal ternary-solvent-ink strategy is proposed for the cesium lead halides (CsPbX

This paper reports a multi-functional terahertz (THz) metamaterial based on a nano-imprinting method. The metamaterial is composed of four layers: 4 L resonant layer, dielectric layer, frequency selective layer, and dielectric layer. The 4 L resonant structure can achieve broadband absorption, while the frequency selective layer can achieve transmission of specific band. The nano-imprinting method combines electroplating of nickel mold and printing of silver nano-particle ink. Using this method, the multilayer metamaterial structures can be fabricated on ultrathin flexible substrates to achieve visible light transparency. For verification, a THz metamaterial with broadband absorption in low frequency and efficient transmission in high frequency is designed and printed. The sample’s thickness is about 200 µm and area is 65 × 65 mm2. Moreover, a fiber-based multi-mode terahertz time-domain spectroscopy system was built to test its transmission and reflection spectra. The results are consistent with the expectations.

Since the layer erosion often happens during the solution-processable optoelectronic devices, and thus the efficiency of inkjet-printed quantum dot light emitting diodes (QLEDs) lags behind those of spin-coated counterparts severely. Indeed, the pursuit of high-performance inkjet-printed QLEDs is fundamentally challenging. Herein, a binary QDs ink based on cyclohexylbenzene (CHB) and indane was developed with red CdZnSe/ZnS core/shell structure without using any other additives for inkjet printing. Three common hole transport materials (HTMs), poly (9-vinlycarbazole) (PVK), poly[(9,9'-dioctylfluorenyl-2,7- diyl)-co-(4,4'-(N-(4-sec-butyl))diphenylamine)] (TFB) and poly (N, N′-bis (4-butylphenyl-N, N′-bis (phenyl) benzidine) (Poly-TPD), were invoked as the underlying layer to print QDs emissive layer, and their surface wettability and solvent resistance were systematically investigated. Among them, PVK exhibited excellent surface wettability and solvent resistance, accordingly, the PVK-based printed red QLEDs exhibited the current efficiency of 28.8 cd A−1 and the maximum external quantum efficiency (EQE) over 17.0%, which was comparable to the spin-coated QLEDs (19.8%). These results demonstrate the fabrication of efficient inkjet-printed QLED devices, which will be meaningful for printed QLEDs displays.

Two new N,N-chelated difluoroboron complexes, PIBF2-Cz and PI-BODIPY, containing phenanthroimidazole moiety were synthesized and characterized by elemental analysis, NMR spectroscopy and MS. Their photophysical and electrochemical properties and thermal stabilities were investigated systematically. The results showed that these N,N-chelated difluoroboron complexes not only exhibit excellent thermal stabilities but also emit strong green emissions with photoluminescence quantum efficiency of 95.71% and 67.22% in chloroform solutions. Furthermore, based on these N,N-chelated difluoroboron complexes, the green organic light-emitting devices with a configuration of ITO/NPB (20 nm)/TBADN: difluoroboron complex (x wt%, 30 nm)/TPBi (30 nm)/Liq (2 nm)/Al (100 nm) have been successfully fabricated by vacuum-deposition method, in which the devices fabricated from PIBF2-Cz exhibited the best electroluminescence performance with a maximum brightness of 20290 cd/m2 and a maximum luminous efficiencies of 7.97 cd/A and a maximum external quantum efficiency (EQE) of 1.88%.

Silver nanowires (AgNWs) have been widely used in transparent conductive films (TCFs) for wearable optoelectronic devices due to their high transmittance, high conductivity. Mask-assisted vacuum filtration is a straightforward and effective patterning strategy for AgNWs with high aspect ratio. However, currently reported non-erasable masks result in the filter membrane being unable to be recycled, which greatly increase the manufacturing cost of patterned TCFs. Herein, we propose an improved method to construct an erasable mask on the filter membrane by screen printing polyvinyl alcohol (PVA) solution. The printed PVA mask is strongly attached to the filter membrane, which lead to the AgNWs pattern with smooth and distinct edges after vacuum filtration. The deposited AgNWs patterns can be transferred to the polydimethylsiloxane film by hot pressing to prepare the patterned TCFs. After the transfer, the printed PVA mask can be easily erased or cleaned from the filter membrane in hot water without damaging its pore structure, enabling the recycling of the filter membrane. As a proof, ten pieces of TCFs with square shape were prepared by recycling one filter membrane and all of them had excellent consistency in sheet resistance, optical transmittance and bending durability. Alternating current electroluminescence devices made from the TCFs were consistent in luminance, emission spectrum and Commission Internationale de l’eclairage coordinates. The erasable mask technique can be extended to patterning process of various nanomaterials other than AgNWs under vacuum filtration to enhance the utilization efficiency of filter membrane and to reduce the manufacturing cost.