Kalyan Yoti Mitra

All-inkjet printed organic transistors: Dielectric surface passivation techniques for improved operational stability and lifetime

Abstract We report about the use of a printed pentafluorothiophenol layer on top of the dielectric surface as a passivation coating to improve the operational stability of all-ink-jet printed transistors. Transistors with bottom-gate structure were fabricated using cross-linked poly-4-vinylphenol (c-PVP) as dielectric layer and an ink formulation of an amorphous triarylamine polymer as semiconductor. The resulting TFTs had low turn-on voltage (Vth

Upscaling of the Inkjet Printing Process for the Manufacturing of Passive Electronic Devices

This paper demonstrates the manufacturing of inductor coils, capacitors, and rectifying diodes solely using the inkjet printing technology. Industrially relevant printheads from Fujifilm Dimatix were employed to prove the process scalability of the inkjet printing technology by manufacturing hundreds of devices. Organic and inorganic conductors and different organic dielectrics were applied for the manufacturing of electrical devices as well as a p-type organic semiconductor. The manufacturing yield effects of varying printing parameters, such as print resolution (drop spacing) and the size of the printed area on the layer morphology and electrical characteristics, were investigated.

Inkjet printed metal insulator semiconductor (MIS) diodes for organic and flexible electronic application

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.

Time-Efficient Curing of Printed Dielectrics via Infra-Red Suitable to S2S and R2R Manufacturing Platforms for Electronic Devices

Inkjet technology is commonly used as a nonimpact, versatile, and additive digital manufacturing/printing technology. The flexibility offered by this technology toward deposition accuracy, usage, industrial upscaling relevance, and even testing of various solution processable functional materials, e.g., conductors and insulators, makes it very attractive for printed electronic applications. The focus of this paper is improving the curing time durations for inkjet-printed polymeric dielectric layers. In this paper, enhancement with regard to curing time durations is performed and they were found to be reduced dramatically down to less than 1 min using Infrared (IR) emitters, whereas the state-of-the-art curing demands a minimum of 60 min. Here in the experiments, inkjet printing was done using conductive and dielectric inks for developing fundamental devices like a capacitor. The sintering of silver electrodes was done using a conventional oven, and curing of the polymeric dielectric was done using a conventional oven as well as IR radiation. Observations are made on the basis of the dielectric insulation between the top and bottom electrodes for the capacitors containing dielectrics cured in conventional oven and those which are cured using IR radiation under two different manufacturing platforms, i.e., sheet to sheet and roll to roll.

Fabrication of Organic Photo Detectors Using Inkjet Technology and Its Comparison to Conventional Deposition Processes

The current upscaling of large area electronics is pushing the technological and cost limits of conventional processing and materials. Introduction of new materials, sophisticated device architectures and advanced deposition techniques has made organic photo detector (OPD) attractive for many applications. Spin coated Titanium Oxide (TiOx) has been successfully established as an electron transport layer (ETL) in many optoelectronic devices, including OPDs. In this paper, on one hand OPDs are fabricated with TiOx as ETL deposited by sputtering and electron beam techniques, where the dark current density is reduced by two orders of magnitude up to 10−7 A/cm2 while retaining high photo responsivity. On the other hand, inkjet printing is demonstrated as an alternative additive and digital manufacturing route for the vacuum-free deposition of TiOx and active layer composition of poly(3-hexylthiophene) and [6,6]-phenyl-C60-butyric acid methyl ester (P3HT:PC60BM). OPDs fabricated with inkjet printed TiOx layers showed comparable performance as the state of the art devices fabricated by spin coated TiOx. In addition, OPDs were manufactured using inkjet technology for both the active and ETL layers. Our research proves that there is a significant influence of the deposition technique to the corresponding device performance. The results obtained in terms of figure of merit for OPDs (dark current density of

Controlling the crack formation in inkjet-printed silver nanoparticle thin-films for high resolution patterning using intense pulsed light treatment

2.7\times 10^{-5}

Investigation on Electrical Stress over Metal-Insulator-Metal (MIM) Structures Based on Compound Dielectrics for the Inkjet-Printed OTFT Stability

A/cm2, signal to noise ratio of 320, external quantum efficiency of 45% and fabrication yield of 30%–60%) from the developed inkjet printing process shows that further investigation on the ink formulation and optimizations can result into better performing OPDs.

Up-scaling of the manufacturing of all-inkjet-printed organic thin-film transistors: Device performance and manufacturing yield of transistor arrays

During the last years, intense pulsed light (IPL) processing has been employed and studied intensively for the drying and sintering of metal nanoparticle layers deposited by means of printing methods on flexible polymer substrates. IPL was found to be a very fast and substrate-gentle approach qualified for the field of flexible and large-area printed electronics, i.e. manufactured via roll-to-roll processing. In this contribution, IPL is used for the fine-patterning of printed silver nanoparticle layers. The patterning is obtained by induced and controlled crack formation in the thin silver layer due to the intense exposure of IPL. The crack formation is controlled by selection of the substrate material, the fine-tuning of the morphology of the silver layer and an application of a dielectric layer on top of the silver layer that acts as a stress concentrator. Careful optimization of the IPL parameters allowed to adjust the lateral width of the crack. This novel approach turned out to be a fast and reproducible high-resolution patterning process for multiple applications, e.g. to pattern the source-drain electrodes for all-inkjet-printed thin-film transistors.

All-inkjet-printed low-pass filters with adjustable cutoff frequency consisting of resistors, inductors and transistors for sensor applications

One of the greatest challenges in the field of printed electronics is the performance stability of the devices fabricated by the different printing technologies e.g. inkjet or gravure printing technology. The performance instability can be defined in terms of the device breakdown or by other effects like the emergence of leakage current under the constant high voltage inputs (especially the dielectric within the transistor architecture). The reasons behind this phenomenon can be various, but the most prominent indication can be detected from the materials used and the deposition methodology. For this purpose the herein work is presented, targeting on the all inkjet-printed organic thin film transistor (OTFT), but keeping the focus on the basic building block for fabricating inkjet-printed OTFTs. In this case it is the metal-insulator-metal (MIM) layer structure. Herein, the MIM structures are inkjet-printed, and then characterized optically and electrically. The dielectric layers for the MIM structures are printed using three different dielectric ink materials either individually 1) Single component system; or in combination with each other as in form of bi-layer stack 2) Multiple component system. The thickness of the printed dielectric layers is varied for these MIM structures. The electrical characterization is performed with respect to current vs. applied voltage and is done for a large number of iterations. The leakage current is of interest and shows a negative and positive trend towards the single component system and multiple component system for the dielectric layers in the MIM characterization structures respectively.