On the Effects of Strain in Intrinsically Stretchable OECTs

Organic electrochemical transistors (OECTs) are mixed conductor devices that rely on the interaction between electronic and ionic transport and are widely used due to their ability to interface with a biological environment as well as their low operating voltages^[1,2]. Only recently, efforts have been attributed to develop (intrinsically) stretchable OECTs, realizing conformable devices such as soft implants^[3] and health monitoring devices^[4]. To advance next-generation stretchable OECTs, it is essential to investigate the fundamental relationships between strain-induced morphological changes and the OECT performance. From this, reliable design principles can be derived.

The intrinsically stretchable OECTs presented herein were fabricated using our previously reported transfer-printing and patterning method^[5] and thus are based on poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) on stretchable poly(alcoholvinyl) (PVA)-substrates infused with a plasticizer. We compared two configurations of the fully stretchable OECTs: a parallel arrangement, where the strain was aligned with the direction of the drain current, and a perpendicular arrangement, where the strain was applied orthogonally. Notably, the devices were tested without applying any pre-strain, enabling a fundamental analysis of the effects of strain on the morphology and the electrical performance (e.g. transfer characteristics). Our findings revealed opposite trends for each configuration, with the parallel arrangement showing a 26 % increase in transconductance at maximum strain (80 %). Additionally, we explored the impact of strain-induced morphological changes of PEDOT:PSS. Our results e.g. revealed anisotropic behavior of the hole mobility with an increase in the parallel arrangement and a decrease in the perpendicular arrangement. Our work contributes to the fundamental understanding of stretchable OECTs and thus to advance next-generation applications.

[1] J. Rivnay et al.: Adv. Mater. 2013, 10.1002/adma.201303080
[2] P. Lin et al.: Adv. Mater. 2012, 10.1002/adma.201103334
[3] W. Lee etal.: Sci. Adv. 2018, 10.1126/sciadv.aau2426
[4] Y. Dai et al.: Adv. Mater 2022, 10.1002/adma.202201178
[5] C. Volkert et al.: J. Mater. Chem. 2024, 10.1039/d3tc04485h