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This paper details how two new small molecules, based on phenanthrene, were developed, and tailored for light-emitting device applications. An account is provided of both the compound synthesis and the methodologies employed in device fabrication. The ink formulation was improved by the use of triflate counterions. Standard bottom emitting devices were constructed on ITO glass along with top emitting devices on a sputter coated silver on glass substrate. Both structures exhibit UV emissions from the synthesized molecules. Successful EL emission within the UV spectrum range has been achieved by spray coating these active molecules onto glass slides. The optimized solution-processed devices produce UV emission using a semi-transparent silver nanowire top electrode. This results in electroluminescence (EL) peaking at 398 nm, with a maximum EL emission intensity of 20.5 μW/cm2. [Display omitted] • Synthesized two novel UV light-emitting organic materials achieving high electroluminescent intensity of 20.5 μW/cm2. • Spray coating process suitable for top emitting OLECs with AgNW top electrodes demonstrated. • Hexyl imidazolium moiety enhances solubility and enables uniform spray-coated thin films without aggregation or pinholes. [ABSTRACT FROM AUTHOR]

The use of sustainable, multifunctional inks in printed electronics has great utility for various devices, particularly at soft biointerfaces. Here, we discuss the development of a multifunctional nanocomposite ink, termed PS-IO-N ink, designed for applications, principally in the field of flexible and bio-electronics. The ink combines electrically conductive properties with magnetic capabilities, offering a dual-functionality that facilitates both physical and electrical connections. The PSION ink is composed of two main components: poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), a conducting polymer with favorable biocompatibility, and iron oxide (Fe 3 O 4) nanoparticles known for their ferromagnetic properties. The ink is formulated as a stable water dispersion, making it eco-friendly and suitable for aqueous processing. Key findings include the optimization of components to balance electrical conductivity and magnetic behavior, allowing the ink to function as both a physical connector and a conductor. The addition of an adhesion promoter enhances the ink's water stability and surface adhesion. The ink's applicability is demonstrated in various scenarios, such as forming flexible circuits on substrates like paper and silk fibroin, creating temporary magnetic connections for electronic devices, and enabling stable connections to sensors for parameter monitoring. The PSION ink provides an innovative solution for flexible and bioelectronic applications, offering the potential for reversible, adaptable connections in both dry and wet environments. [Display omitted] • Discuss a multifunctional water based ink. • Stable dispersion with conductive and magnetic properties. • Can facilitate transient on/off connections. • Easily dispensed on variety of substrates as micropatterns. • Connections to sensors and other functional devices shown. [ABSTRACT FROM AUTHOR]

Solution-processable organic semiconducting materials have been utilized for low-cost disposable flexible electronics applications through additive printing techniques. Organic electrochemical transistors (OECTs) are powerful devices for biosensing due to their simplicity, stability in aqueous media and high transconductance. Here, we report fully 3D printed functional OECTs using fused deposition modelling (FDM) and direct writing 3D printing techniques using PEDOT:PSS as the channel material with silver as the source/drain material. These devices demonstrate high transconductance of 12.1 ± 0.4 mS, low operating voltage and high current ON/OFF ratio. They have a threshold voltage in the range of 0.66 ± 0.01 V. These printed OECTs demonstrate good stability and robust behavior after several measurement cycles. We demonstrate pH and K+ ion sensing using these printed OECTs with high sensitivity of −26.4 mV/pH and 240 mV/decade (higher than the Nernst limit of 59.2 mV/decade). These devices can be utilized for biosensing and logic circuitry for different wearable and standalone sensing applications. Image 1 [ABSTRACT FROM AUTHOR]

Flexible Organic Field-Effect Transistors (OFETs) constitute nowadays a highly promising field of the organic and printed electronics due to their multiple applications (flexible displays, sensors etc.). However, their cost-effective fabrication by large area Roll-to-Roll compatible printing methods still remains a challenge for their integration to commercial products. In this work, the moderate speed (1 m/min) process of the flexible cross-linked Poly(4-vinyl phenol) (PVP) polymer gate dielectric layer was carried out by integrating a slot-die method that mimics the Roll-to-Roll (R2R) coating conditions, in combination to an airbrush spray method for the solution-processing of the 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-PEN) organic semiconductor. Particularly, the PVP dielectric was slot-die-coated over a 90 × 15 cm2 substrate, while subsequently the TIPS-PEN semiconductor was sprayed onto the 15 × 20 mm2 cPVP-patterned plastic substrates. Α surface investigation study on the well-formed slot-die-coated cPVP strips was conducted, revealing desirable dielectric film topography as a result of the good control over the coating process. A detailed analysis of the cPVP thickness evolution along the 90 × 1.3 cm2 patterned stripe, was carried out. The morphological analysis of the sprayed TIPS-PEN layer over the cPVP film revealed well-organized large crystalline domains across the channel area, as a result of the sufficient crystallization time and the excellent cPVP surface morphology. The fabricated bottom gate/top contact flexible OFETs exhibited excellent I-V electrical characteristics with a maximum mobility of 0.21 cm2/V, negligible hysteresis, low threshold voltages (average value of −0.1 V) and on/off current ratios in the range of 103 to >104. These results demonstrate the potentiality of the proposed scalable methods for the large scale fabrication of high performance low-cost OFET devices. Image 1 • Slot-die coating of cPVP dielectric film onto 90 × 15 cm2 PET/IMI substrate. • Smooth slot-die-coated cPVP films with RMSR values in the range of 0.5–0.7 nm. • Spray-coating of TIPS-Pentacene semiconductor onto slot-die-coated cPVP dielectric. • Well-ordered large-sized crystalline domains across the device channel area. • Mobility values up to 0.21 cm2/Vs, negligible hysteresis, on/off current ratio 103 to >104. [ABSTRACT FROM AUTHOR]

Functional model inks were formulated and printed using flexography in order to assess the influence of ink extensional elasticity and print velocity on the morphological and electrical properties of printed layers. Increased extensional elasticity and higher print velocity resulted in the printing of more isotropic prints, both morphologically and electronically. Furthermore, a correlation between the prints' morphological and electrical anisotropy strongly suggests that print uniformity has a considerable influence on functionality and that ink rheology may be used to control such characteristics. Image 1 • Ink rheology was used to control flexographic print properties. • Extensional elasticity of PEDOT:PSS inks was manipulated with polyacrylamide. • Increasing ink extensional elasticity and print velocity enhanced print isotropy. • Strong correlation was found between morphological and electrical print anisotropy. [ABSTRACT FROM AUTHOR]

Aligned silver nanowire (AgNWs) conductive electrodes are printed through an electrohydrodynamic (EHD) jet printing via cone-jet mode. We investigate effects of poly(ethylene oxide) (PEO) addition to AgNW inks in terms of surface energy, ink viscosity, and electrical conductivity. The optimized PEO content in the ink is determined to be ∼10 wt%, at which well-defined AgNWs/PEO composite electrodes aligned along the printing direction can be prepared by cone-jet mode of EHD jet printing. We fabricate bottom contact organic thin film transistors (OTFTs) with TIPS-pentacene/PS blend as a semiconducting layer to take advantage of printed AgNWs/PEO electrodes. The resulting devices exhibit stable transfer characteristics for 12 h even in ambient air with average field-effect mobility (μ FET), threshold voltage (V th) and on/off current ratio (I on / I off) of 0.51 cm2/V, −2.0 V, and ∼106, respectively. To understand the characteristics of OTFTs based on AgNWs/PEO composite electrodes in detail, we examine crystalline morphology and molecular orientation of TIPS-pentacene/PS blend on various substrates through field emission scanning electron microscopy and two-dimensional grazing incidence X-ray diffraction, respectively. Image 1 • The optimization of EHD jet printing of AgNWs conductive S/D electrodes. • The cone-jet mode of EHD jet printing exhibits well-defined and aligned AgNWs networks. • OTFT employing printed AgNWs/PEO composite S/D electrode exhibited high performance. [ABSTRACT FROM AUTHOR]

Abstract Flexible and lightweight printed thermoelectric devices are becoming increasingly attractive with the advent of ubiquitous sensing and within the context of an increasing energy demand and the associated environmental issues. In this study, flexible thermoelectric devices based on efficient solution-processed organic/hybrid thermoelectric materials have been successfully patterned. The n-type component hexylammonium titanium disulfide (TiS 2 (HA) x) nanocomposite reaches a ZT of 0.08 ± 0.06 at room temperature and was successfully printed on a flexible substrate using inkjet technology which yielded a functional device. The device operates in a near-ambient temperature range and retains its performance under mechanical bending, demonstrating thus the flexible properties of the device. Graphical abstract Image 1 Highlights • TiS2(HA)x hybrid nanocomposite optimized for thermoelectric generation (ZT near 0.1). • Ink formulation of TiS2(HA)x for inkjet printing. • Patterning of a fully printed flexible OTEG device on paper substrate. • Characterization of the device operating at near ambient temperature. • Good accordance of experimental results with numerical values (power density up to 17.6 μWcm-2). [ABSTRACT FROM AUTHOR]

Abstract Thin film transistors (TFTs) constitute important components employed in several printed electronic applications. Many electronic devices comprise TFTs, and their performances are determined by transistor specifications. As such, the optimum performance of a TFT assumes paramount importance in electronic applications. This paper reports the enhanced performance of an organic TFT (OTFT) achieved through use of the structural scaling technique employed during the gravure printing process. Extremely thin 30 nm-thick gravure printed Ag was used as source-drain electrodes while dielectric and semiconductor layers were gravure printed using D series and SP series from Merck, respectively. By scaling thicknesses of the source–drain electrode and dielectric layer, the electrical performance of an OTFT was found to have improved, during the roll-to-roll gravure printing process, in terms of an enhanced mobility of 0.295 cm2 V-1 s-1 and an on–off current ratio of 106. Additionally, OTFTs fabricated using the proposed roll-to-roll gravure printing process exhibit a yield percentage of 95% with a maximum operating speed of 15 m min−1. Furthermore, the OTFT demonstrated uniform electrical characteristics owing to use of an amorphous polymer semiconductor, which reduces the variability of each transistor. Graphical abstract Image 1 Highlights • Sharp channel length and pattern edge were appropriately fulfilled by high printing speed of 15 m min−1. • The study fabricated OTFT devices by employing a 3-layer roll-to-roll and single-layer inkjet printing processes. • Highly thin about 30 nm-thick Ag source–drain electrode layer contributes to an enhanced yield percentage. • Roll-to-roll gravure and inkjet printed OTFT shows excellent performance compared with other previous study of solution processed polymer OTFT. [ABSTRACT FROM AUTHOR]

A new fabrication method to realize fully-printed organic photodiode (OPD) arrays capable of RGB light separation is presented. From the photocurrents generated by each pixel type under the light from RGB LEDs, we demonstrate that this “White”, “Yellow” and “Red” array can successfully detect and reconstruct colors in the RGB system, with an average accuracy of 98.5%. A flexible broadband OPD array is printed on PEN substrate by blade-coating PEDOT:PSS, a polyethylenimine cathode interlayer and the photo-active layer, and screen-printing on top a patterned PEDOT:PSS anode. The OPD array achieves an average EQE of ∼37% at −4 V bias over the whole visible spectrum, 5 orders of magnitude of linear dynamic range (LDR), a 0.5 nA/cm 2 dark current, and maintains these performances in ambient conditions for more than 30 h. Pixels detecting “White”, “Yellow” and “Red” are fabricated by spray-coating two color filters. The substrate is used as a separator between the filters and OPD array. This physical separation allows solution processing of the filters regardless of their electrical properties or of the compatibility of their solvents with the OPD, thus broadening the choice of filter materials while offering a simple fabrication process. The combination of broadband OPD and broadband filters used in this configuration can significantly simplify the fabrication of spectrally-selective photosensors and full-color imagers. [ABSTRACT FROM AUTHOR]

We report herein a fast optical inspection technique for the operation of large-area active-matrix (AM) backplanes by means of gate modulation (GM) imaging measurements. The technique is based on highly sensitive difference-image sensing between alternately biased gate-on and gate-off states for optical microscope images with many AM pixels. The use of a high-frame-rate complementary-metal-oxide-semiconductor image sensor and a high-speed image-subtraction module facilitates the bulk inspection of 30,000 pixels within 3 min, as is demonstrated using an all-printed and flexible AM backplane composed of one-transistor–one-capacitor cells arranged at a 150 pixel-per-inch resolution. We also demonstrate that the technique is very useful and effective not only in quickly identifying both defective transistors and capacitors by examining a zoomed-out image, but also in identifying the origin of defects within channel layers or capacitors by investigating an expanded image. [ABSTRACT FROM AUTHOR]

The surface roughness of a gate dielectric layer has a large effect on the electrical performance of a printed OTFT (Organic Thin Film Transistor). In this study, a treatment process called calendering is proposed to improve the electrical performance of a printed OTFT by reducing the surface roughness of the gate dielectric layer. Bottom-gate, bottom-contact structural p-type OTFT samples were fabricated by gravure printing (gate electrode and gate dielectric), inkjet printing (source/drain electrodes), and spin coating (p-type channel). Various calendering process conditions composed of temperature, speed, and nip pressure were applied in the fabrication process. Then the calendering process was optimized using the grey-based Taguchi method. For validation of the proposed method, surface roughness of the gate dielectric layer and electrical performance of the non-calendered and calendered OTFT samples were compared and analyzed. The experimental results show a significant improvement that is a 15.92% decrease in the surface roughness, a 15.46% increase in the on-off ratio, and a 30.50% increase in the field-effect mobility. [ABSTRACT FROM AUTHOR]

The mass production of organic photovoltaics requires high throughput processes capable of producing a functional active layer which is homogenous, pinhole free and of a specified thickness. Common methods to achieve this are slot-die coating and gravure printing. We have demonstrated the fabrication of poly( N -9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole (PCDTBT) based photovoltaic cells using the flexographic printing technique, which enables high throughput patterned active layers to be deposited on flexible substrates at lower cost. This was achieved by optimizing the flexographic plate pattern, print speed, the solvent and the drying process. By incorporating halftone patterning, a common process in the graphics printing industry, and optimizing the printing speed, the homogeneity of the active layer print was significantly improved. Further studies of suitable solvents and drying conditions led to reduced pinhole formation and improved uniformity. The functionality of the flexographically printed active layer was demonstrated by fabrication of 1 cm 2 photovoltaic cells which showed an efficiency of up to 3.5%, which is comparable to alternative deposition techniques. These results demonstrate the suitability of flexography as a fabrication technique for bulk heterojunction organic photovoltaics. [ABSTRACT FROM AUTHOR]

A direct-writing fabrication process for fully inkjet-printed short-channel organic thin-film transistors (OTFTs) has been developed. Channels as narrow as 800 nm between two printed Ag electrodes were achieved by printing a special Ag ink on an SU-8 interlayer, which can be partially dissolved by the solvents used in the Ag ink. The ridge formed along the printed Ag line edges due to redistribution of the interlayer material during the drying process limits the ink spread, and separates neighboring printed lines, and is the key to defining an ultra-narrow channel for transistor fabrication. The short-channel OTFTs fabricated using this technique have demonstrated well-defined linear and saturation regimes. An extracted mobility of 0.27 cm 2 /Vs with an on/off ratio of 10 5 was obtained at a driving voltage of −12 V. The excellent performance of these devices demonstrates the potential of this technique in fabrication of short-channel devices using standard printing technologies. [ABSTRACT FROM AUTHOR]

Neuromorphic circuits that mimic the operation of nerve cells are promising approaches to interface with or emulate the operation of biological neural networks. These types of electronic circuits have generally been realised by fabrication using well-established silicon technology but herein we report the fabrication of a simple neuromorphic circuit, specifically, an integrate-and-fire (I&F) circuit, using solution-processed OFETs. It consists of p-type organic field-effect transistors (OFETs) realised with parylene-dielectric, printed silver electrodes and a solution processed semiconductor on a flexible plastic substrate. As the behaviour of the fabricated I&F circuit is predictable by simulation, the reported process allows for customised circuit design and provides the basis to realise a variety of flexible neuromorphic circuit designs. [Display omitted] • Neuromorphic circuits can mimic the electrical spiking of nerve cells. • A simple neuromorphic circuit made using printed organic field-effect transistors. • Performance of a printed integrate and fire circuit can be modelled by simulation. [ABSTRACT FROM AUTHOR]

Productive manufacturing that uses a roll-to-roll process, called printed electronics, is highly demanded for low-cost, large-area, and high-speed fabrication of organic devices. However, although most studies on the printing process have been focused on the deposition of films, few studies are reported on solution methods for anisotropic etching that are compatible with the printing process. Studying anisotropic etching by using a wet process is a matter of great importance for the further development of printed electronics. Here, we conduct anisotropic etching by using an electrospray method, one of the wet processes, on an underlying active layer beneath source and drain electrodes and demonstrate a reduction in the parasitic resistance of organic field-effect transistors. The same equipment for the etching as the deposition of films was consistently used. Therefore, this study will pave the way for sophisticating printed electronics. [Display omitted] • TIPS pentacene/PMMA blend films and PMMA etch masks were prepared by ESD. • We conducted anisotropic etching by using an electrospray method (a wet process). • Underlying TIPS pentacene beneath source/drain electrodes was selectively etched. • We demonstrated a clear reduction in the parasitic resistance of top-contact OFETs. • The same ESD system for the etching as the deposition of films was consistently used. [ABSTRACT FROM AUTHOR]

In this work, all ink-jet printed (IJP) low-voltage organic field-effect transistors (OFETs) on flexible substrate are reported. The OFETs use IJP silver (Ag) for source/drain/gate electrodes, poly(4-vinylphenol) (PVP) for gate dielectric, 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene) blended with polystyrene (PS) as the semiconducting layer and CYTOP for encapsulation layer. All the printing processes were carried out in ambient air environment using a single laboratory ink-jet printer Dimatix DMP-2831. The all IJP device presents state-of-the-art performance with low operation voltage down to 3 V, small subthreshold swing ( SS ) of 0.155 V/decade, mobility of 0.26 cm 2 V −1 s −1 , threshold voltage ( V th ) of −0.17 V and on/off ratio of 3.1 × 10 5 , along with a yield of 62.5%. Through interface engineering and proper process optimization, this work demonstrates a promising low-voltage all IJP device platform for low-cost flexible printed electronics. [ABSTRACT FROM AUTHOR]

Low-cost and flexible first and second order low-pass filters with adjustable cutoff frequency were designed and printed by inkjet printing technology. The all-inkjet-printed low-pass filters were characterized and an adjustable cutoff frequency feature in form of an inkjet-printed organic thin-film transistors (OTFTs) was added to the filters for application-oriented fine-tuning. The applicability of these small circuits was evaluated by signal filtering for sensor applications. As a result, low-pass filters with an adjustable cutoff frequency ranging from 82 Hz to 740 Hz were obtained, demonstrating their suitability in signal filtering and their promising applicability for tactile sensing characterized by low frequency signals. [ABSTRACT FROM AUTHOR]

We present a morphological and electrical analysis of inkjet-printed two-dimensional films of silver nanoparticle inks arranged at different orientation to the raster-scan-based printing process. Different parameters causing morphological and functional irregularities in the inkjet-deposited films as a function of their orientation to the printing process are introduced in detail and the relevance for the field of printed electronics is discussed. Researchers have demonstrated the manufacturing of various microelectronic devices using inkjet printing. Nearly all of the devices are based on simple rectilinear geometries. Usually, these geometries have a preferential orientation that is exactly (i) along the deposition process or exactly (ii) perpendicular to the deposition process. So far, it was assumed that the geometrical and functional characteristics are identically for the both cases. However, we show empirically that this is not the case and help to understand the conditions that lead to the differences. [ABSTRACT FROM AUTHOR]

A novel acceptor building block, 3,7-bis(( E )-2-oxoindolin-3-ylidene)-3,7-dihydrobenzo[1,2- b :4,5- b′ ]dithiophene-2,6-dione (IBDT), is developed to construct a donor-acceptor polymer PIBDTBT-40 . This polymer has favorable highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels for balanced ambipolar charge transport. Organic thin film transistors (OTFTs) based on this polymer shows well-balanced ambipolar characteristics with electron mobility of 0.14 cm 2 V −1 s −1 and hole mobility of 0.10 cm 2 V −1 s −1 in bottom-gate bottom-contact devices. This polymer is a promising semiconductor for solution processable organic electronics such as CMOS-like logic circuits. [ABSTRACT FROM AUTHOR]

All-inkjet-printed thin-film transistors (TFTs) have been demonstrated in literature using mainly laboratory inkjet equipment, simple one-channel layout and only a low number of manufactured TFT devices. We report on the development and the up-scaling of the manufacturing of all-inkjet-printed TFT arrays using industrial inkjet equipment. The manufacturing of the TFTs was carried out in ambient condition without the need for cleanroom environments or inert atmospheres and at a maximum temperature of 150 °C enabling the use of flexible polymer films as substrate. Arrays of 924 TFTs were manufactured on an area of about DIN A4 (297 × 420 mm 2 ). This allows the consideration of statistics, e.g. to determine the process yield as a function of device design and layout. We present process yields for all-inkjet-printed TTFs up to 82% demonstrating the potential of the developed all-inkjet-printing process. [ABSTRACT FROM AUTHOR]

The deposition of a thin and uniform dielectric layer is required for high performance printed capacitors and thin film transistors (TFTs), however this is difficult to achieve with printing methods. We have demonstrated inkjet-printed dielectrics with a uniform thickness from 70 nm to 200 nm by taking advantage of the coffee ring effect. A high capacitance per unit area of 230 pF/mm 2 is achieved from capacitors with linear morphologies fully printed onto flexible substrates. We also demonstrate organic TFTs with an average mobility of 0.86 cm 2 /Vs and a source drain current of 57 μA obtained with a supply voltage of 15 V. This performance was shown to be consistent, with a standard deviation of 15% obtained from hundreds of printed organic TFTs on PET substrates. This consistency was further validated by the production of functional NAND, NOR, AND and OR logic gates. Our results demonstrate that the coffee ring effect, which is usually viewed as undesirable, can enable higher performance in printed electronic devices. [ABSTRACT FROM AUTHOR]

Single-walled carbon nanotubes (SWNTs) are a valuable material for use in not only nanoelectronics but also printed electronics because of their stability, tunable operation speed, and scalability. However, the device characteristics of fully printed, SWNT-based thin film transistors (SWNT-TFTs) often have large variations, and the fundamental cause of these inconsistencies are not yet well understood. Therefore, fully printed SWNT-TFT-based electronic devices have not been practically realized in the market. In this study, the significant variation in the electrical parameters of printed SWNT-TFTs that is caused by minor molecular variations in the formulation of silver nanoparticle-based ink is reported. Strikingly, a very small difference in the chemical structure between ethylene glycol and diethylene glycol in the silver nanoparticle-based ink, which is used to print drain-source electrodes in the SWNT-TFTs, with everything else identical, induced a difference of approximately 70 meV in the barrier height between the drain-source electrodes and the SWNT layer at 300 K. The modification of the absorbed polymer binder in the silver nanoparticle ink due to the additive is the major cause of the observed barrier height difference. These results allow for a better understanding of the relationship between the ink rheology at the molecular level and the printed device properties, and enable a more precise design and control of device properties which will have profound impacts on printed electronic devices. [ABSTRACT FROM AUTHOR]

Printed organic thin-film transistors (OTFTs) are promising for flexible, low-cost electronics; however, a major challenge is that successive processing steps of multiple solution-processed layers can interfere with each other. In particular, hydrophobic fluoropolymers are a promising group of materials to fabricate gate dielectrics with low charge trap density and properties such as good thermal stability, chemical inertness, low dielectric constant, and water repellency. However, the main difficulty in incorporating hydrophobic fluoropolymers in printed electronic devices is their low surface energy. Plasma treatment is a common method for surface modification that renders these hydrophobic layers wettable to print subsequent layers. This plasma processing can also affect the interface with the organic semiconductor (OSC) and transistor performance, which is studied here for the first time. The morphological and surface chemical properties of Teflon amorphous fluoropolymer (Teflon-AF) films change after plasma treatment and gradually reverse after post-annealing of subsequent layers as demonstrated here. Here, we fabricate solution-processed OTFTs with Teflon-AF as the gate dielectric. We report OTFTs with inkjet-printed source and drain electrodes with a minimum channel length of 20 μm on Teflon-AF for the first time. We show that the annealing of the inkjet-printed electrodes changes the morphology and the surface chemistry of the Teflon-AF gate dielectric underneath, thus reversing the effect of the plasma. We show that this electrode post-annealing step can improve the transistor performance by improving the interface between the Teflon-AF gate dielectric and the OSC in terms of smoothness and hydrophobicity. The transistor parameters such as mobility, on/off current ratio, and threshold voltage all follow a trend explained here by the properties of the Teflon-AF films. Increasing the post-annealing temperature to just below complete surface reversibility decreases surface roughness and trap-sites created after plasma treatment leading to optimized device performance. We characterize the Teflon-AF surface with contact angle measurement, roughness measurement, Fourier transform infrared spectroscopy (FTIR), and x-ray photoelectron spectroscopy (XPS). This understanding of the reversibility of the Teflon-AF surface helps achieve optimal performance of devices and systems incorporating fluoropolymers. [Display omitted] • The challenge of processing OTFT layers on hydrophobic dielectrics is addressed. • 20 μm channel OTFTs with inkjet-printed electrodes on hydrophobic dielectric are achieved. • Teflon-AF surface changes after plasma and reverses after post-annealing. • Electrode annealing changes the morphology and surface chemistry of the dielectric. • Electrode annealing can improve the gate dielectric/organic semiconductor interface. [ABSTRACT FROM AUTHOR]

Hybrid organic-inorganic composites offer solution processability and ease to construct opto-electronic devices with diverse functionalities, which are desirable for applications like flexible and printed electronics. Trigonal Selenium (t-Se) has been recently investigated for photodetector application, owing to its inherent superior optical properties such as high absorption coefficient and photoconductivity. However, most of the reported Selenium photodetectors use vapor transport based device fabrication techniques which require controlled environments and face scalability issues. In this work, high-performance photodetector based on Selenium-PEDOT:PSS hybrid junction is demonstrated using a facile sonication assisted mechanical mixing and drop-casting technique. XRD and Raman analysis reveals the existence of Selenium in trigonal crystal structure and FE-SEM images show clustered nanoparticles. Selenium is mixed with PEDOT:PSS to form bulk heterojunction, which enhances the electron-hole pair separation efficiency and results in improved device responsivity. Also, due to the favorable band offset between Selenium and PEDOT:PSS which results in built-in field, the photodetector operates in self-biased mode. The device exhibits broad spectral response in UV–Vis–NIR range with responsivities of 0.56 A/W, 66 mA/W and 1.363 A/W at 315 nm, 620 nm and 820 nm, respectively. Response times of 7.7 s, 9.4 s and 6.4 s and external quantum efficiencies (EQE) of 192.58%, 13.25% and 206.55% are obtained for UV, Vis and NIR spectra respectively. Further to validate the robustness, the device is subjected to multiple bending cycles (∼2500) and minimal degradation in performance is observed. Given the simple device architecture and facile device fabrication scheme, this work would enable promising approach for high performance flexible photodetectors. [Display omitted] • Selenium, possesses high absorption co-efficient and high photoconductivity with optical bandgap of 1.2–1.5 eV. • However, t-Se has been less explored for photodetector applications. • This work reports a solution-processed hybrid-heterojunction based on Se-PEDOT:PSS for photodetection. • The detector exhibits spectral response from UV–Vis to NIR and significant performance at zero bias condition. [ABSTRACT FROM AUTHOR]

Printed Electronics (PE) on flexible substrates (e.g. plastic-film) is an emerging technology that potentially complements silicon-based electronics. To facilitate the design and realization of PE analog and digital circuits for the augmentation of signal processing thereto, we present in this paper, a novel and comprehensive printed transistor model that is simple, accurate and compatible with industry-standard IC (integrated circuit) electronic design automation tools. Unlike reported models, the proposed comprehensive model accommodates and accurately models the effect of the channel length on carrier mobility, leakage current and parasitic capacitances, and is valid for all transistor operating regions, from cut-off to supra-threshold regions. The proposed comprehensive model further embodies process variations (statistical data) and matching based on various layout techniques. These comprehensive modelings are imperative for the practical design and simulation of PE circuits, including manufacturability and implications with respect to the challenges of PE circuits. On the basis of the proposed comprehensive model, several fundamental analog and digital PE circuits, based on conventional and novel methods, are designed and realized on plastic-films. Their measured parameters agree well with that obtained from simulations (using the model derived herein), depicting the efficacy of the comprehensive model. This model is particularly useful as it provides invaluable insights to PE circuit and system designers. [ABSTRACT FROM AUTHOR]

Printed electronics represent an alternative solution for the manufacturing of low-temperature and large area flexible electronics. The use of inkjet printing is showing major advantages when compared to other established printing technologies such as gravure, screen or offset printing, allowing the reduction of manufacturing costs due to its efficient material usage and the direct-writing approach without requirement of any masks. However, several technological restrictions for printed electronics can hinder its application potential, e.g. the device stability under atmospheric or even more stringent conditions. Here, we study the influence of specific mechanical, chemical, and temperature treatments usually appearing in manufacturing processes for textiles on the electrical performance of all-inkjet-printed organic thin-film transistors (OTFTs). Therefore, OTFTs where manufactured with silver electrodes, a UV curable dielectric, and 6,13-bis(triisopropylsilylethynyl) pentance (TIPS-pentacene) as the active semiconductor layer. All the layers were deposited using inkjet printing. After electrical characterization of the printed OTFTs, a simple encapsulation method was applied followed by the degradation study allowing a comparison of the electrical performance of treated and not treated OTFTs. Industrial calendering, dyeing, washing and stentering were selected as typical textile processes and treatment methods for the printed OTFTs. It is shown that the all-inkjet-printed OTFTs fabricated in this work are functional after their submission to the textiles processes but with degradation in the electrical performance, exhibiting higher degradation in the OTFTs with shorter channel lengths ( L = 10 μm). [ABSTRACT FROM AUTHOR]

Filamentary conduction and switching properties are studied in printed rectifying diodes with a poly(triaryl amine) (PTAA) semiconductor layer sandwiched between Cu and Ag electrodes. Formation of conductive filaments caused defective operation of the rectifier at low frequencies. In contrast, the normal operation was restored at high frequencies. Reversible switching was observed between the low and high frequency states. Therefore, it is clear that the operational frequency has a significant effect on the filament formation and switching characteristics. The filamentary conduction was confirmed by lock-in IR thermography and physical defect analysis. The results reveal the existence of filamentary operation in p-type rectifying diodes and clearly demonstrate the effect of the device operation frequency on the switching properties. This has far-reaching implications on the switching properties in similar devices in literature. [ABSTRACT FROM AUTHOR]

In this contribution we show a simple approach for the development of all-polymer based complementary logic circuits fabricated by printing on plastic, at low temperature and in ambient conditions. This is achieved by patterning, with a bottom-up approach, solely synthetic carbon-based materials, thus incorporating earth-abundant elements and enabling in perspective the recycling – a critical aspect for low-cost, disposable electronics. Though very simple, the approach leads to logic stages with a delay down to 30 μs, the shortest reported to date for all-polymer circuits, where each single component has been printed. Moreover, our circuits combine bendability and high transparency, favoring the adoption in several innovative applications for portable and wearable large-area electronics. [ABSTRACT FROM AUTHOR]

For the solution processing of organic photovoltaics on an industrial scale, the exclusion of halogenated solvents is a necessity. However, the limited solubility of most semiconducting polymer/fullerene blends in non-halogenated solvents results in ink formulations with low viscosities which poses limitations to the use of roll-to-roll compatible deposition processes, such as inkjet printing. We propose to add polystyrene as a rheological modifier to increase the viscosity of bulk heterojunction (BHJ) non-halogenated inks. The printing and performance of P3HT/PCBM photoactive layer inks are characterized as a function of polystyrene concentration and three different molecular weights. Addition of 1 wt% polystyrene provided a near two-fold gain in viscosity, with the largest viscosity gains coming from the polymer with the highest molecular weight. However, this coincided with greater viscoelastic behavior, which reduced the jetting performance of the inks. Differences in solvent compatibility of the polystyrene/P3HT/PCBM ternary blend resulted in phase separation upon layer drying, whereby polystyrene segregated to the layer-air interface to form an isolated domain or network like topology. Nevertheless, a 1.7-fold increase in dynamic viscosity was obtained for devices with printed BHJ layers containing polystyrene at the expense of a 20% reduction in OPV performance. The improved viscosity and good printing behavior achieved with small additions of polystyrene demonstrates its potential to overcome the limited viscosity resulting from typical non-halogenated ink formulations for semiconducting polymers. These results offer a step forward to the industrialization of inkjet printing as an effective deposition technique for functional layers of organic electronics. [ABSTRACT FROM AUTHOR]

TIPs-pentacene OFETs were fabricated on a plastic substrate using polymer nanocomposite dielectric. The blend polymer P(VDF-TrFE)/PMMA (30 wt%) was used as polymer matrix and BaTiO 3 nanoparticles modified by 3-glycidoxypropyltrimethoxysilane (GPTMS) were dispersed as ceramic fillers. The effects of different loadings of BaTiO 3 on the surface morphology and electrical properties of dielectric films were investigated. The formulation of screen-printable dielectric ink of P(VDF-TrFE)/PMMA/BaTiO 3 /Silica (SII) was achieved by adding fumed silica as the viscosity modifier. TIPs-pentacene OFETs using SII as the gate dielectric features a mobility of 0.01 cm 2 /V s, and having a threshold voltage of −6 V. This screen-printable dielectric ink is promising for low operating-voltage fully-printed OFETs. [ABSTRACT FROM AUTHOR]

A novel, solution processed high- k nanocomposite/low- k polymer bilayer gate dielectric that enables the fabrication of organic field-effect transistors (OFETs) that operate effectively at 1 V in high yields is reported. Barium strontium titanate (BST) and barium zirconate (BZ) nanoparticles are dispersed in a poly (vinylidene fluoride-co-hexafluoropropylene) P(VDF-HFP) polymer matrix to form a high- k nanocomposite layer. This is capped with a thin layer ( ca 30 nm) of cross-linked poly(vinyl phenol) (PVP) to improve the surface roughness and dielectric–semiconductor interface and reduces the leakage current by at least one order of magnitude. OFETs were fabricated using solution-processed semiconductors, poly(3,6-di(2-thien-5-yl)-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione)thieno[3,2-b]thiophene) and a blend of 6,13-bis (triisopropylsilylethynyl) pentacene and poly (α-methylstyrene), in high yield (>90%) with negligible hysteresis and low leakage current density (10 − 9 A cm − 2 at ±1). [ABSTRACT FROM AUTHOR]

This work presents a simple, low-cost and practical inkjet-printing technique for fabricating an innovative flexible gas sensor made of graphene–poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) composite film with high uniformity over a large area. An electronic ink prepared by graphene dispersion in PEDOT:PSS conducting polymer solution is inkjet-printed on a transparency substrate with prefabricated electrodes and investigated for ammonia (NH 3 ) detection at room temperature. Transmission electron microscopy, Fourier transform infrared spectroscopy, UV–visible spectrometer and Raman characterizations confirm the presence of few-layer graphene in PEDOT:PSS polymer matrix and the present of π–π interactions between graphene and PEDOT:PSS. The ink-jet printed graphene–PEDOT:PSS gas sensor exhibits high response and high selectivity to NH 3 in a low concentration range of 25–1000 ppm at room temperature. The attained gas-sensing performance may be attributed to the increased specific surface area by graphene and enhanced interactions between the sensing film and NH 3 molecules via π electrons network. The NH 3 -sensing mechanisms of the flexible printed gas sensor based on chemisorbed oxygen interactions, direct charge transfers and swelling process are highlighted. [ABSTRACT FROM AUTHOR]

Highly photosensitive organic phototransistors (OPTs) are successfully demonstrated on a flexible substrate using all-solution process as well as a combination of printing methods which consist of roll-to-plate reverse offset printing (ROP), inkjet printing and bar coating. Excellent electrical switching characteristics are obtained from heterogeneous interfacial properties of the reverse-offset-printed silver nanoparticle electrode and the inkjet-printed p -channel polymeric semiconductor. In particular, the OPTs exhibit remarkably photosensitivity with a photo-to-dark current ratio exceeding 5 orders. This optoelectronic properties of the combinational printed OPTs are theoretically and experimentally studied, and found the comparable tendency. In addition, excellent mechanical stability is observed with up to 0.5% of strain applied to the OPTs. Hence, by manufactured with a combination of various graphic art printing methods such as roll-to-plate ROP, inkjet printing, and bar coating, these devices are very promising candidates for large-area and low-cost printed and flexible optoelectronics applications. [ABSTRACT FROM AUTHOR]

All inkjet printed piezoelectric actuators based on poly(vinylidene fluoride- co -trifluoroethylene) (P(VDF–TrFE)) for applications as pump actuators in microfluidic lab-on-a-chip systems (LOC) are manufactured and investigated in terms of their morphology and actuator performance. Furthermore, a pump demonstrator with an all-printed P(VDF–TrFE) actuator is characterized here for the first time. The actuators are manufactured in a fully additive and flexible way by successive inkjet printing of a P(VDF–TrFE) film sandwiched between two silver electrodes on a polyethylene terephthalate (PET) substrate. Different from most current micropumps where actuator elements are fabricated separately, no additional joining step is required in the manufacturing approach employed here. Actuator performance is investigated by measurements of piezoelectric d 31 coefficients as well as remanent polarization P rem for different thermal treatments of the as-printed P(VDF–TrFE) films. A strong dependence of the device performance on the annealing temperature is found with maximum values for d 31 and P rem of approximately 10 pm V −1 and 5.8 μC cm − 2 , respectively. Morphology investigations of the printed films by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and Atomic Force Microscopy (AFM) indicate an increased degree of crystallinity of the piezoelectric β-phase for samples annealed at temperatures above 110 °C, which coincides with improved device performance. A basic pumping function with pump rates of up to 130 μL min − 1 is demonstrated, which is promising for future applications in LOC. Furthermore, the process chain and characterization presented here can be employed to design and manufacture also other P(VDF–TrFE)-based devices and allows the combination with additional printed on-chip functionalities in future LOC. [ABSTRACT FROM AUTHOR]

We have demonstrated fast operation of printed organic inverter circuits. We employ a soluble organic semiconducting material which has high field-effect mobility and ink-jet printed source/drain electrodes with short channel length. Appropriate concentration of the semiconducting solution and modification layer of source/drain electrodes improve both mobility and on/off ratio. The fabricated transistors with a short channel length (4 μm) exhibit excellent mobility (1.2 cm 2 /V s), high on/off ratio (>10 5 ) and operational stability. The diode-load inverter with a narrow channel and low parasitic capacitance operate at 8 kHz at 20 V. These results will lead to significant progress in applications of printed organic circuits. [ABSTRACT FROM AUTHOR]

Highlights: [•] We suggest a global classification for the manufacturing of organic electronics. [•] Viable alternatives to roll-to-roll (R2R) exist. We discuss four principles. [•] We comment on the chances and limitations of each substrate transport principle. [•] Selection of a substrate transport principle is based on various attributes. [•] We present a hierarchy of attributes and discuss their impact on OPV, OLED and OFET. [Copyright &y& Elsevier]

Highlights: [•] Developed Fully-Additive printing process shows high carrier mobility. [•] Demonstrate of Fully-Additive printed amplifier with gain comparable with the subtractive processes. [•] Demonstrate of fully-additive printed DAC with very good INL and DNL. [ABSTRACT FROM AUTHOR]

Highlights: [•] Low-voltage passive-matrix electrochromic displays manufactured by printing tools. [•] A threshold voltage is obtained in a simple three-layer pixel architecture. [•] The threshold voltage enables unique pixel addressability in the resulting display. [•] The electrolyte is deposited by using a novel surface energy patterning method. [•] The results promise for true low-cost manufacturing of flexible displays. [Copyright &y& Elsevier]

Highlights: [•] A method for improving the PCE of solution processed inverted solar cells. [•] The origin of the improvement is the enhanced hole selectivity of inverted OPVs. [•] Different boiling points wetting agents in PEDOT:PSS improve the device fill factor. [•] The proposed additive mixture in PEDOT:PSS improves reliability of the results. [•] The proposed PEDOT:PSS treatment improves 12% the PCE of the inverted OPVs. [ABSTRACT FROM AUTHOR]

Abstract: We report the development of high-performance inkjet-printed organic field-effect transistors (OFETs) and complementary circuits using high-k polymer dielectric blends comprising poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)) and poly(methyl methacrylate) (PMMA) for high-speed and low-voltage operation. Inkjet-printed p-type polymer semiconductors containing alkyl-substituted thienylenevinylene (TV) and dodecylthiophene (PC12TV12T) and n-type P(NDI2OD-T2) OFETs showed high field-effect mobilities of 0.1–0.4cm2 V−1 s−1 and low threshold voltages down to 5V. These OFET properties were modified by changing the blend ratio of P(VDF-TrFE) and PMMA. The optimum blend – a 7:3wt% mixture of P(VDF-TrFE) and PMMA – was successfully used to realize high-performance complementary inverters and ring oscillators (ROs). The complementary ROs operated at a supplied bias (V DD) of 5V and showed an oscillation frequency (f osc) as high as ∼80kHz at V DD =30V. Furthermore, the f osc of the complementary ROs was significantly affected by a variety of fundamental parameters such as the electron and hole mobilities, channel width and length, capacitance of the gate dielectrics, V DD, and the overlap capacitance in the circuit configuration. [Copyright &y& Elsevier]

Abstract: Symmetric and fast (∼5ms) on-to-off and off-to-on drain current switching characteristics have been obtained in screen printed organic electrochemical transistors (OECTs) including PEDOT:PSS (poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonic acid)) as the active transistor channel material. Improvement of the drain current switching characteristics is made possible by including a carbon conductor layer on top of PEDOT:PSS at the drain electrode that is in direct contact with both the channel and the electrolyte of the OECT. This carbon conductor layer suppresses the effects from a reduction front that is generated in these PEDOT:PSS-based OECTs. In the off-state of these devices this reduction front slowly migrate laterally into the PEDOT:PSS drain electrode, which make off-to-on switching slow. The OECT including carbon electrodes was manufactured using only standard printing process steps and may pave the way for fully integrated organic electronic systems that operate at low voltages for applications such as logic circuits, sensors and active matrix addressed displays. [Copyright &y& Elsevier]

Abstract: We report a method for inkjet-printing an organic semiconductor layer on top of the electrolyte insulator layer in polyelectrolyte-gated OFETs by using a surface modification treatment to overcome the underlying wettability problem at this interface. The method includes depositing an amphiphilic diblock copolymer (P3HT-b-PDMAEMA). This material is designed to have one set of blocks that mimics the hydrophobic properties of the semiconductor (poly(3-hexylthiophene) or P3HT), while the other set of blocks include polar components that improve adhesion to the polyelectrolyte insulator. Contact angle measurements, atomic force microscopy, and X-ray photoelectron spectroscopy confirm formation of the desired surface modification film. Successful inkjet printing of a smooth semiconductor layer allows us to manufacture complete transistor structures that exhibit low-voltage operation in the range of 1V. [Copyright &y& Elsevier]

Abstract: Organic integrated circuits based on organic thin-film transistor (TFT) devices are fabricated with solution-based electrodes by using dense inks of silver nanoparticles, which can be sintered at room-temperature. The TFT devices fabricated at a sintering temperature of 30°C exhibit good electrical characteristics. There is a strong relation between the sintering temperature of silver nanoparticle inks and transistor characteristics. A work function of silver electrodes can be controlled by changing the sintering temperature of silver nanoparticle inks, thereby threshold voltage of fabricated TFT devices are shifted accordingly. Fabricated pseudo-CMOS inverter circuits are successfully operated at low voltage with small hysteresis, and large gains are obtained. These results suggest that printed organic TFT devices fabricated with a low-temperature process enable large-area and low-cost integrated circuits by using these techniques in future applications. [Copyright &y& Elsevier]

Abstract: We report on the first fully mass printed large-area piezoelectric loudspeakers on paper. All functional layers were printed by means of flexography, alternatively screen and stencil printing, on conventional paper without any surface modification. We used polymers for the electrodes (poly(3,4-ethylendioxythiophene)/poly(4-styrenesulfonate, PEDOT:PSS)) as well as the piezoelectric layer (poly(vinylidene fluoride-trifluorethylene), P(VDF-TrFE)). It could be demonstrated that low-cost devices for mass markets can be realized successfully with the developed technology and process. Besides technical challenges, electrical and acoustic properties of printed speakers are investigated, taking the mechanical properties of the substrate and size of the active piezoelectric area into account. A sound pressure level up to 80dB could be achieved. [Copyright &y& Elsevier]

Abstract: Poly(3,4-ethylenedioxythiophene) chemically doped with poly(styrene sulfonic acid) (PEDOT:PSS) is a material system commonly used as a conductive and transparent coating in several important electronic applications. The material is also electrochemically active and exhibits electrochromic (EC) properties making it suitable as the active element in EC display applications. In this work uniformly coated PEDOT:PSS layers were used both as the pixel electrode and as the counter electrode in EC display components. The pixel and counter electrodes were separated by a whitish opaque and water-based polyelectrolyte and the thicknesses of the two EC layers were varied independently in order to optimize the color contrast of the display element. A color contrast (ΔE ∗, CIE L ∗ a ∗ b ∗ color space) exceeding 40 was obtained with maintained relatively short switching time at an operational voltage less than 2V. [Copyright &y& Elsevier]

Abstract: A fully printed ring oscillator circuit is reported, which has not only horizontally arranged parts, but inverter stages stacked vertically on top of each other in four through-connected substrate layers. For the preparation of the inverters exclusively gravure and flexographic printing were used. Characteristics of the stacked ring oscillator are similar to planar circuits. A very interesting path of development for printed electronics is opened with this approach, because three-dimensional circuits become possible. [Copyright &y& Elsevier]

Abstract: Organic thin film transistors with channel lengths below 20μm have been fabricated on plastic substrates using a combination of rotogravure and ink-jet printing exclusively. Gravure is utilized to deposit thin, smooth, and narrow metal lines ideal for gate electrodes; a poly(4-vinylphenol) dielectric; and a poly(2,5-bis(3-tetradecylthiophene-2-yl)thieno[3,2-b]thiophene) (pBTTT) semiconductor using a heated roll. A novel fluid guiding technique is used to maintain closely spaced ink-jet printed source and drain (S/D) contacts. Together these printing processes yield aggressively scaled yet easily manufacturable TFTs with operating frequencies of 18kHz. [ABSTRACT FROM AUTHOR]