Ultra-high-resolution printing of flexible organic thin-film transistors

Xuying Liu,Masayuki Kanehara,Chuan Liu,Takeo Minari

doi:10.1080/15980316.2017.1298538

Abstract

ABSTRACTFully printed electronics on plastic have attracted considerable interest owing to their high compatibility and ease of integration. Here, an ultra-high-resolution printing technique based on parallel vacuum ultraviolet patterning that can produce high-contrast wettability regions on flexible substrates was developed. This technique was used to selectively deposit a functional ink with a 1 µm feature size, thereby allowing the large-scale fabrication of organic thin-film transistors with channels as short as 1 µm under an ambient atmosphere. Moreover, in short-channel devices, hole injection barriers can be tuned by printing the optimum gate overlaps associated with selectively doping semiconductor/electrode interfaces, resulting in a marked reduction in contact resistance from 20 to 1.5 kΩ cm, and an elevation of the charge carrier mobility to a record high of 0.3 cm2 V−1 s−1 in a 1-µm-channel device. The results indicate that the developed technique is promising for the fabrication of large-area, high-resolution, low-cost electronics.

Highlights

Shrinking device dimensions to the few-micron scale is the primary step in manufacturing high-resolution electronics
5-μm-channel polymer OTFTs prepared via inkjet printing exhibited a field effect mobility of 0.02 cm2 V−1 s−1 [5], whereas when the channels were further downscaled to hundreds of nanometers, much lower μFET values ranging from 0.001 to 0.005 cm2 V−1 s−1 were observed [8]
A dramatic increase in mobility accompanied by a decrease in threshold voltage (Vth) can be clearly seen from 1 to 50 μm in Figure 3(b), which reveals that the charge carrier transport was strongly limited by contact injection [16], especially in the shortchannel devices

Summary

Introduction

Shrinking device dimensions to the few-micron scale is the primary step in manufacturing high-resolution electronics. For devices with channel lengths less than 10 μm, the short-channel effect highly dominates the device performance; parameters such as series parasitic resistance, channel length, apparent threshold voltage, and apparent field effect mobility (μFET) are taken into account in constructing the model. 5-μm-channel polymer OTFTs prepared via inkjet printing exhibited a field effect mobility of 0.02 cm V−1 s−1 [5], whereas when the channels were further downscaled to hundreds of nanometers, much lower μFET values ranging from 0.001 to 0.005 cm V−1 s−1 were observed [8]. To obtain high performance in short-channel devices, the optimum gate overlap length was printed with high precision, in combination with the controllable modification of the metal/organic semiconductor interface via fully solution-based processes to reduce the contact resistance to 1.5 k cm, which is an order of magnitude lower than that in unoptimized devices. The μFET was enhanced to as high as 0.3 cm V−1 s−1 in the 1-μm-channel OTFTs, which, to the best of the authors’ knowledge, is a recordhigh value

Experiment

Results and discussion

Conclusion

Notes on contributors