Flexible TFTs based on solution-processed ZnO nanoparticles

Abstract

Flexible electronic devices which are lightweight, thin and bendable have attracted increasing attention in recent years. In particular, solution processes have been spotlighted in the field of flexible electronics, since they provide the opportunity to fabricate flexible electronics using low-temperature processes at low-cost with high throughput. However, there are few reports which describe the characteristics of electronic devices on flexible substrates. In this study, we fabricated flexible thin-film transistors (TFTs) on plastic substrates with channel layers formed by the spin-coating of ZnO nanoparticles and investigated their electrical properties in the flat and bent states. To the best of our knowledge, this study is the first attempt to fabricate fully functional ZnO TFTs on flexible substrates through the solution process. The ZnO TFTs showed n-channel device characteristics and operated in enhancement mode. In the flat state, a representative ZnO TFT presented a very low field-effect mobility of 1.2 x 10(-5) cm(2) V(-1) s(-1), while its on/off ratio was as high as 1.5 x 10(3). When the TFT was in the bent state, some of the device parameters changed. The changes of the device parameters and the possible reasons for these changes will be described. The recovery characteristics of the TFTs after being subjected to cyclic bending will be discussed as well.

Improving electrical performance and bias stability of HfInZnO-TFT with optimizing the channel thickness

“…The threshold voltages are 7.4, 4.2, 3.7 and −4.7 V for TFTs with 20, 30, 40, and 60 nm HfInZnO channels, respectively. The threshold voltage can be expressed as: 15,16 …”

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.…”

“…The use of barrier layers for flexible ntype solution-processed metal oxide semiconductor devices is not very common. A few examples include c-PVP layers applied to planarize and smoothen the surface of PES or PI, 191,226 as well as PVP films utilized to reduce the surface roughness of PI foils from 3.6 nm down to 0.3 nm (root mean square). 232 145,197 Nevertheless, for solution-deposited metal oxide semiconductors, it is preferable to solution process also the gate dielectric, in order to further benefit from the lowcost large-area approach offered by solution-deposition processes.…”

Flexible Electronics: Integration Processes for Organic and Inorganic Semiconductor-Based Thin-Film Transistors

“…The deformation is instead released through the nanoparticle network. Therefore, the TFT threshold voltage is constant during the bending test; however, the deformation of the ZnO film causes a variation of the physical distance between nanoparticles, which influences the transistor current level, as reported by Jun et al [35].…”

“…It maintains an attractive cost base and has almost no influence on the transistor integration process. After the nanoparticle deposition, an annealing process removes the solvent [34][35][36].…”