Printed electronics promises the realization of low-cost electronic systems on flexible substrates over large areas. In order to achieve this, high quality patterns need to be printed at high speeds. Gravure printing is a particularly promising technique that is both scalable and offers micron-scale resolution. Here, we review the tremendous progress that has recently been made to push gravure printing beyond its traditional limitations in the graphic arts. Rolls with far greater precision than traditional rolls and with sub-5 μm resolution can be fabricated utilizing techniques leveraging the precision of silicon microfabrication. Physical understanding of the sub-processes that constitute the gravure process is required to fully utilize the potential of gravure. We review the state-of-the-art of this understanding both for single cells and patterns of multiple cells to print high-resolution features as well as highlyuniform layers. Finally, we review recent progress on gravure printed transistors as an important technology driver. Fully high-speed printed transistors with sub-5 μm channel length and sub-5 V operation can be printed with gravure.
Extensive research on organic field-effect transistors (OFETs) performed to date investigated separately the electronic contact and the gate dielectric interfaces but rarely probed the relation between the two. In this report, the strong impact of the gate dielectric on the contact resistance (R c ) is revealed. With the same semiconductor dioctylbenzothienobenzothiophene (C8-BTBT) and the same device configuration, the R c value varies greatly from 10 to 66 kΩ•cm depending on the gate dielectric interfaces. Also, the gatevoltage dependency of R c exhibits an unexpectedly large discrepancy when different dielectrics are used. Intuitive comprehension points to the possibility that the gate dielectric interface affects the morphology of semiconductor and thus the charge injection. However, from microstructure study, albeit the semiconductor film exhibits structural defects on certain dielectrics, the impact on the injection is not crucial. Instead, bias-stress test correlates well with the contact resistance on different dielectric interfaces. At a quantitative level, gate-voltage-dependent R c can be described by taking into account the different charge trapping induced by the gate dielectrics. The origin of the varied R c is thus attributed to the trapped charges, which screen the gate field and reduce the carrier mobility simultaneously. A general method is proposed to examine whether the charge injection is significantly influenced by the charge trapping effect due to the gate dielectrics.
Additive patterning of transparent conducting metal oxides at low temperatures is a critical step in realizing low cost transparent electronics for display technology and photovoltaics. In this work, inkjet printed metal oxide transistors based on pure aqueous chemistries are presented. These inks readily convert to functional thin films at lower processing temperatures (T ≤ 250 °C) relative to organic solvent-based oxide inks, facilitating the fabrication of high-performance transistors with both inkjetprinted transparent electrodes of aluminum-doped cadmium oxide (ACO) and semiconductor (InO x ). The intrinsic fluid properties of these water-based solutions enable the printing of fine features with This article is protected by copyright. All rights reserved. 2 coffee-ring free line profiles and smoother line edges than those formed from organic solvent-based inks. The influence of low temperature annealing on the optical, electrical, and crystallographic properties of the ACO electrodes is investigated, as well as the role of aluminum doping in improving these properties. Finally, we characterize the all-aqueous printed TFTs with inkjet-patterned semiconductor (InO x ) and source/drain (ACO) layers, which show ideal low contact resistance (R c < 160 Ω-cm) and competitive transistor performance (µ lin up to 19 cm 2 V -1 s -1 , SS ≤ 150 mV dec -1 ) with only low temperature processing (T ≤ 250 °C).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.