Approaches to Stretchable Polymer Active Channels for Deformable Transistors

Abstract

The fabrication of deformable devices has been explored by interconnecting nonstretchable unit devices with stretchable conductors or by developing stretchable unit devices consisting of all stretchable device components such as electrodes, active channels, and dielectric layers. Most researches have followed the first approach so far, and the researches based on the second approach are at the very beginning stage. This paper discusses the perspectives of the second approach, specifically focusing on the polymer semiconductor channel layers, that is expected to facilitate high density device integration in addition to large area devices including polymer solar cells and light-emitting diodes. Three different routes are suggested as separate sections according to the principles imparting stretchability to polymer semiconductor layers: structural configurations of rigid semiconductors, two-dimensional network structure of semiconductors on elastomer substrates, and ductility enhancement of semiconductor films. Each section includes two subsections divided by the methodological difference. This Perspective ends with discussion on the future works for the routes and the challenges related to other device components.

Current Status and Opportunities of Organic Thin-Film Transistor Technologies

“…First, the stack of organic semiconductor (OSC) and polymer gate dielectric with low temperature and fast annealing processes is compatible with low-cost high-throughput printing-based manufacturing [9], and also provides excellent intrinsic mechanical flexibility [10], [11] or even stretchability [12], [13] for truly flexible and stretchable electronics. Second, OSCs have great potential for continuous performance improvement and functionalization through molecule structure tailoring [14], [15] and physical blending [16], which opens a model of boosting the product performance or creating product differentiation by changing the active materials instead of the manufacturing facilities.…”

Stretchable and ultraflexible organic electronics

“…13 Chortos et al have used intentionally cracked (but electrically contiguous) semiconductor fi lms 19 ( Figure 3b ), and Lee et al used another approach in which the semiconducting channel comprises a network of nanofi bers in a stretchable matrix. 8 We note the importance of encapsulation for improving the stability of fl exible and stretchable devices. In the case of fl exible applications, use of encapsulation allows the researcher to put the most sensitive components in the mechanically neutral plane; in the case of stretchable applications, encapsulation redistributes strain evenly across the active materials such that strain is not concentrated at thin areas and defects, which are ordinarily the sites where cracks initiate ( Figure 3c-d ).…”

“…7 Other approaches that are applicable only to organics, however, give them a distinct advantage, such as the formation of fi bers to form elastic mats and the synthesis of materials whose molecular structure or solid-state packing structure permits extreme deformation. 8 A suite of tools incorporating metrology, synthesis, and fabrication has recently emerged whose goal is to achieve the original dream of organic electronics-to combine state-of-the-art electronic performance with high deformability. This research is, at present, somewhat distinct from efforts in the fi eld to understand and to improve the electronic properties of organic semiconductors, though ultimately, the results of both spheres of inquiry must be merged.…”

Block copolymer structural color strain sensor

“…In our previous work, numerous screw dislocations a few micrometers in size developed in a BCP film 39 . When mechanical tensile stress is applied to a ductile film on an elastic substrate, the microcracks will deform slowly and withstand repeated loading and unloading cycles 40 . We speculate that the centers of individual dislocations, which serve as channels for the ionic liquid, are responsible for efficient release of the mechanical stress exerted on the PS domains.…”