Reliable inkjet contact metallization on printed polymer semiconductors for fabricating staggered TFTs

Abstract

Even though the fundamental benefits of the staggered bottom-gate top-contact geometry in organic thin-film transistors (TFTs) have been fully demonstrated for enhancing the charge injection efficiency, most printed organic TFTs with inkjet-printed source/drain electrodes have only been fabricated in bottom-contact configurations, probably due to the difficulty of printing with metal-nanoparticle ink on soluble organic semiconductor (OSC) without film deformation/dissolution. Here, we present the printing process and the electrical characteristics of inkjet-printed top contact OSC in bottom-gate TFTs. We first fabricated polymer bottom-gate TFTs by printing in two different top- and bottom-contact configurations. The physical carrier mobility of the two TFTs was extracted from a gated-contact organic TFT model to exclude the effect of geometric contact resistance RC. When compared to assess the OSC film damage from the printing metallization, the two mobility values were almost identical. This result indicates that the metal nanoparticle ink used in this work formed a top metal contact on the OSC film without significant chemical damage. Furthermore, the printed top-contact TFT exhibited I–V characteristics almost identical to those of a thermally evaporated Ag top-contact TFT. This study suggests the possibility of inkjet-printed top metal contacts for organic thin-film devices such as transistors, solar cells, and diodes.

Spatiotemporal Measurement of Arterial Pulse Waves Enabled by Wearable Active-Matrix Pressure Sensor Arrays

“…Active-matrix sensor arrays based on printed TFT arrays are also rare (Table S3). In addition to our previously developed fundamental inkjet printing design rules, − the advanced design rule for large-area electronic devices and delicately optimized fabrication process in this work made it possible to develop ultrathin (2 μm) TFT arrays with a 100% yield and high uniformity (RSD < 10%).…”

“…The cartridge and platen temperatures were set at 40 and 50 °C, respectively. Layout-to-bitmap conversion and design rules are explained in our previous works, − and their extension into large-area arrays is described in Figure S1.…”

Layout-to-Bitmap Conversion and Design Rules for Inkjet-Printed Large-Scale Integrated Circuits

“…In 2020, the authors discussed a charge injection efficiency of AgNP contacts by comparing thermally evaporated Ag contacts. The results showed a comparable contact resistance in inkjet-printed staggered TFTs by the use of directly printed S/D electrodes on a conjugated polymer . The authors recently developed nonvolatile TFT-based memory devices fabricated by using the fab process discussed in this paper .…”

“…The results showed a comparable contact resistance in inkjet-printed staggered TFTs by the use of directly printed S/D electrodes on a conjugated polymer. 51 The authors recently developed nonvolatile TFT-based memory devices fabricated by using the fab process discussed in this paper. 13 The authors believe that their previous reported results demonstrate the reliability and the extendibility of the current study to the fabrication of flexible LSI system applications.…”

Unified electrical model for the contact regions of staggered Thin Film Transistors

“…Nevertheless, most OTFTs have been fabricated in BC configurations because of the process difficulty of making source/drain (S/D) metal electrodes on top of the organic semiconductor layer with precise patterning [30,31]. Recent advances on inkjet contact metallization on printed polymer semiconductors can reverse this trend in favor of staggered TFTs [32]. In order to be prepared for this scenario, a proper model to describe the staggered configuration is necessary, despite it being more complex model with more parameters.…”