Inkjet Printed, High Mobility Inorganic-Oxide Field Effect Transistors Processed at Room Temperature

Abstract

Printed electronics (PE) represents any electronic devices, components or circuits that can be processed using modern-day printing techniques. Field-effect transistors (FETs) and logics are being printed with intended applications requiring simple circuitry on large, flexible (e.g., polymer) substrates for low-cost and disposable electronics. Although organic materials have commonly been chosen for their easy printability and low temperature processability, high quality inorganic oxide-semiconductors are also being considered recently. The intrinsic mobility of the inorganic semiconductors are always by far superior than the organic ones; however, the commonly expressed reservations against the inorganic-based printed electronics are due to major issues, such as high processing temperatures and their incompatibility with solution-processing. Here we show a possibility to circumvent these difficulties and demonstrate a room-temperature processed and inkjet printed inorganic-oxide FET where the transistor channel is composed of an interconnected nanoparticle network and a solid polymer electrolyte serves as the dielectric. Even an extremely conservative estimation of the field-effect mobility of such a device yields a value of 0.8 cm(2)/(V s), which is still exceptionally large for a room temperature processed and printed transistor from inorganic materials.

Metal oxide semiconductor thin-film transistors for flexible electronics

“…If the semiconductor deposition is performed at lower temperatures ( 150 C), also PES foils (T G around 200 C) can be utilized. 226 In an attempt to reduce the substrate cost, especially when cost-effective high throughput fabrication processes are targeted, less expensive (but also less thermally resistance) polymer substrates like PEN 190,[195][196][197]227,228 and PET 76,194,229,230 have been employed. Additionally, the use of paper substrates for flexible solution-processed ZnO TFTs has been investigated.…”

“…II B, electrolyte dielectrics allow achieving high C ox values and therefore low operation voltage typically below 62 V. Examples of electrolyte gated n-type solution-processed metal oxide semiconductor TFTs have been successfully demonstrated on PEN, PI, and paper substrates. 190,193,231 Due to the good conformal coating, electrolyte gate dielectrics facilitate also the deposition of structured/rough metal oxide semiconductors, especially nanoparticles (NPs) and nanorods (NRs).…”

“…The contact materials used in n-type solution-processed metal oxide semiconductor TFTs are generally similar to those employed for their vacuum-processed counterparts. Source/drain and gate electrodes are mostly made of Al and Au, 145,193,231 but also of transparent conducting metal oxides, such as ITO, 76,83,190,196,197 IZO, 220,221 or zinc indium tin oxide (ZITO). 192 In addition to the above mentioned materials, gate contacts are also made of Cr 145 or dual layers of Cr/Au, 220,221 which yield a good adhesion.…”

“…29,115 Alternatives to Ga doping in IZO have also been developed, using tin (Sn), hafnium (Hf), and zirconium (Zr 76 including neat layers, nanoparticle (NP), or nanowire (NW) films, as well as blends of In 2 O 3 and polyvinylpyrrolidon (PVP). 76,145,[190][191][192] 83 either in the form of neat IGZO or in blends of IGZO and graphene nanosheets. 83,200,201 B.…”

“…In general, two approaches can be used to solution-deposit metal oxide semiconducting materials: 236 (A) The material is first synthesized and tailored into nanoparticles, nanorods, or nanowires. 76,190,226,227,230,231,238 These nano-scaled shapes are then dispersed in suitable solvents and subsequently deposited and dried. (B) Alternatively, the precursor solution is first deposited and then converted to the final metal oxide semiconducting material, most commonly via thermal annealing at temperatures in the range of 200 to 500 C, or alternatively via UV irradiation.…”