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. 2021 Dec 15;13(49):59012-59022.
doi: 10.1021/acsami.1c15208. Epub 2021 Dec 4.

Self-Aligned Bilayers for Flexible Free-Standing Organic Field-Effect Transistors

Hanna Zajaczkowska  1 , Lothar Veith  2 , Witold Waliszewski  1 , Malgorzata A Bartkiewicz  2   3 , Michal Borkowski  1 , Piotr Sleczkowski  1 , Jacek Ulanski  1 , Bartlomiej Graczykowski  2   3 , Paul W M Blom  2 , Wojciech Pisula  1   2 , Tomasz Marszalek  1   2
Affiliations

Self-Aligned Bilayers for Flexible Free-Standing Organic Field-Effect Transistors

Hanna Zajaczkowska et al. ACS Appl Mater Interfaces. .

Abstract

Free-standing and flexible field-effect transistors based on 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene)/polystyrene bilayers are obtained by well-controlled phase separation of both components. The phase separation is induced by solvent vapor annealing of initially amorphous blend films, leading to crystallization of TIPS-pentacene as the top layer. The crystallinity and blend morphology strongly depend on the molecular weight of polystyrene, and under optimized conditions, distinct phase separation with a well-defined and trap-free interface between both fractions is achieved. Due to the distinct bilayer morphology, the resulting flexible field-effect transistors reveal similar charge carrier mobilities as rigid devices and additionally pronounced environmental and bias stress stabilities. The performance of the flexible transistors remains stable up to a strain of 1.8%, while above this deformation, a close relation between current and strain is observed that is required for applications in strain sensors.

Keywords: field-effect transistors; flexible free-standing transistor; organic semiconductor; self-aligned bilayer; semiconductor/dielectric blend; trap-free interface.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
(a) Chemical structures of PS and TIPS-pentacene; (b) polarized optical microscopy images of SVA TIPS-pentacene/PS blend films with different Mw of PS; and (c) UV–vis spectra of as-cast (dashed lines) and SVA TIPS-pentacene/PS blend films (solid lines) with different Mw of PS.
Figure 2
Figure 2
(a) TOF-SIMS depth profiles of as-cast and SVA TIPS-pentacene/PS blend films with schematic illustrations of the phase separation and TIPS-pentacene ordering and (b) lateral distribution of characteristic secondary ion signals at the top film surface of SVA TIPS-pentacene/PS blends obtained by TOF-SIMS imaging analysis (dark areas are OFET electrodes as indicated).
Figure 3
Figure 3
(a) Transfer characteristics at VDS = −60 V of OFETs based on SVA TIPS-pentacene/PS blend films with different Mw of PS; (b) transfer characteristics at VDS = −60 V of OFETs based on SVA blends of TIPS-pentacene/366 kDa PS fresh (green) and after 18 months storage in air (blue); (c) transfer characteristics after different stressing times of OFETs based on SVA blends of TIPS-pentacene/366 kDa PS; and (d) cross-sectional scanning electron microscopy (SEM) image of the SVA TIPS-pentacene/366 kDa PS blend and the schematic illustration of the OFET architecture.
Figure 4
Figure 4
(a) Young’s modulus for PS (square), as-cast (circle), and SVA (triangle) TIPS-pentacene/PS blend films with 190 kDa (red), 366 kDa (green), and 492 kDa (blue) PS, (b) IDS as a function of the strain of an OFET based on the SVA TIPS-pentacene/PS blend. The inset shows the bending of the SVA TIPS-pentacene/PS OFET by applying convex buckling through compression (R, radius and ε, strain).
See this image and copyright information in PMC

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