We report on the detailed electrical investigation of all-inkjet-printed thin-film transistor (TFT) arrays focusing on TFT failures and their origins. The TFT arrays were manufactured on flexible polymer substrates in ambient condition without the need for cleanroom environment or inert atmosphere and at a maximum temperature of 150 °C. Alternative manufacturing processes for electronic devices such as inkjet printing suffer from lower accuracy compared to traditional microelectronic manufacturing methods. Furthermore, usually printing methods do not allow the manufacturing of electronic devices with high yield (high number of functional devices). In general, the manufacturing yield is much lower compared to the established conventional manufacturing methods based on lithography. Thus, the focus of this contribution is set on a comprehensive analysis of defective TFTs printed by inkjet technology. Based on root cause analysis, we present the defects by developing failure categories and discuss the reasons for the defects. This procedure identifies failure origins and allows the optimization of the manufacturing resulting finally to a yield improvement.

1wileyonlinelibrary.com and easy-handling devices; however, numerous inherent problems still remain, especially concerning the long-term stability and lack of reliability, that require further studies and standardization before devices can be fully applied in fi eld applications. OTFTs are amenable to the use of multiple substrates and can operate at room temperature. They are especially interesting in biological applications, as they enable the use of a wide range of biocompatible and biodegradable materials detecting a wide range of analytes, including gases (such as NH 3 and NO 2 ), proteins, DNA, bacteria, etc. [ 5 ] However, the performance of these devices is limited by low sensitivity (around several micrograms per milliliter). Large surface-to-volume ratio nanostructures, high-k dielectrics, [ 6 ] or 1D materials such as silicon nanowires, carbon nanotubes, [ 7,8 ] and graphene have been used to enhance the sensitivity. Despite this fact, their fabrication has limitations, requiring sophisticated fabrication techniques to precisely deposit them. Solution-processed inorganic thin-fi lm devices may be promising; nevertheless, organic semiconductors benefi t from relatively low temperature, solution processing capability, and the fl exibility to work on any kind of substrate, with a high mobility. [ 9 ] Regardless of the organic high-performance materials, the limit of detection can be improved by means of: i) different geometries of the OTFT, and, ii) performing detection under the sub-threshold region. [ 10 ] Advances in organic electronics have yielded diverse, lowcost electronic components that have enabled the development of thin, fl exible, and environmental friendly devices. [ 11 ] Unlike traditional inorganic TFTs, which are made by a complicated photolithography processes that requires expensive masks and cleanroom facilities, OTFTs can be easily fabricated by inkjet printing and do not require cleanroom settings. Nevertheless, contemporary OTFTs suffer from certain drawbacks that researchers are currently endeavoring to overcome: high operating voltages, low material stability, and relatively short operating lifetimes.Among the OTFT-based devices, organic fi eld-effect transistors (OFETs) have been selected over organic electrochemical transistors (OECTs) for sensing purposes. The main factors motivating this choice are: i) dielectric functionalization without losing electrical properties of the organic semiconductors, and, ii) reusability device since the transduction mechanism is based on electrostatic gating consisting on a capacitive coupling between the organic semiconductor and the gate in contrast of the electrochemical doping/de-doping mechanism An Inkjet-Printed Field-Effect Transistor for Label-Free BiosensingMariana Medina-Sánchez , Carme Martínez-Domingo , Eloi Ramon , and

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Over the past decade, inkjet technology has been well recognized for the manufacturing of products that include “printing beyond colors.” This micrometer‐scale precise technology provides a straightforward approach toward judicious deposition of electronically functional material inks on various substrates over relatively large areas, for printed/flexible electronics. The technology promotes upscalability and has become a renowned process tool for fabricating electronic devices in the field of printed/flexible electronics. Here, the fabrication of printed thin‐film transistors (TFT) on cheap coated paper substrate using inkjet technology is reported. For developing the TFT layer stack conductive nanoparticle inks, a polymeric dielectric ink and a p‐type organic semiconductor ink are employed. The coating on the paper provides several advantages for fabrication process of TFTs; for example, control over ink spreading. This control of ink spreading can directly influence the fabrication of interdigitated source/drain (S/D) electrodes for TFTs, when a top gate bottom contact architecture is considered. This results in better manufacturing yields and promising electrical performance, which are also the focus of this research. The all inkjet‐printed TFTs on paper exhibit electrical performance with maximum S/D current ranging to 170 nA, charge carrier mobility of 0.087 cm2 V−1 s−1, and current on/off ratio of 330.

The implementation of organic semiconductor (OSC) materials in X‐ray detectors provides exciting new opportunities for developing a new generation of biocompatible devices with high potential for the fabrication of sensitive and low‐cost X‐ray imaging systems. Here, the fabrication of high performance organic field‐effect transistors (OFETs) based on blends of 1,4,8,11‐tetramethyl‐6,13‐triethylsilylethynyl pentacene (TMTES) with polystyrene is reported. The films are printed employing a low cost and high‐throughput deposition technique. The devices exhibit excellent electrical characteristics with a high mobility and low density of hole traps, which is ascribed to the favorable herringbone packing (different from most pentacene derivatives) and the vertical phase separation in the blend films. As a consequence, an exceptional high sensitivity of (4.10 ± 0.05) × 1010 µC Gy–1cm–3 for X‐ray detection is achieved, which is the highest reported so far for a direct X‐ray detector based on a tissue equivalent full organic active layer, and is higher than most perovskite film‐based X‐ray detectors. As a proof of concept to demonstrate the high potential of these devices, an X‐ray image with sub‐millimeter pixel size is recorded employing a 4‐pixel array. This work highlights the potential exploitation of high performance OFETs for future innovative large‐area and highly sensitive X‐ray detectors for medical dosimetry and diagnostic applications.

All inkjet printed rectifying diodes based on a metal-insulator-semiconductor (MIS) layer stack are presented. The rectifying properties were optimized by careful selection of the insulator interlayer thickness and the layout structure. The different diode architectures based on the following materials are investigated: (1) silver/poly (methylmethacrylate-methacrylic acid)/polytriarylamine/silver, (2) silver/polytriarylamine/poly (methylmethacrylate-methacrylic acid)/silver, and (3) silver/poly (methylmethacrylate-methacrylic acid)/poly-triarylamine/poly(3,4-ethylenedioxythiophene) poly (styrenesulfonate). The MIS diodes show an averaged rectification ratio of 200 and reasonable forward current density reaching 40 mA cm −2 . They are suitable for a number of applications in flexible printed organic electronics.

We report on the development of inkjet-printed thin-film resistors using both organic and inorganic ink formulations. The passive devices were manufactured on flexible polymer substrates in ambient condition without the need for a cleanroom environment or inert atmosphere and at a maximum temperature of 150 °C. By using the same manufacturing process, the rapid electrical sintering (RES) method is demonstrated as effective for the fabrication of inkjet-printed, programmable Write-Once-Read-Many (WORM) memories. Several hundred fully inkjet-printed resistors with different parameters were fabricated and subsequently morphologically and electrically characterized with the aim of obtaining statistically significant data. From a manufacturing process viewpoint, the procedures based on inkjet printing herein described are highly attractive: they do not require high temperatures, low pressures, special atmospheric conditions, and any masks, therefore providing a versatile low-cost approach to fabricate passive electrical components and simple circuits useful for the electronic industry. Printing can be carried out at a sufficiently low temperature to avoid damage to the fabric substrate and these devices can be used in a range of applications requiring flexible and conformal devices from embedded passive filters in PCBs to wearable electronics.

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