# Exploring Wide‐Range Alkyl Bridge Length Variations in Polymer Semiconductors: From Pristine to Blend Films for High‐Mobility Stretchable TFTs

## TL;DR

This paper introduces a new method to design stretchable polymer transistors with high performance by adjusting alkyl bridge lengths, enabling durable and flexible electronics.

## Contribution

A systematic study of alkyl bridge length variations in polymer semiconductors to enhance stretchability and charge transport in transistors.

## Key findings

- Optimized polymer achieved 6.4 cm² V⁻¹ s⁻¹ mobility at 0% strain.
- Maintained 0.6 cm² V⁻¹ s⁻¹ mobility at 100% strain.
- Fabricated a 38-device stretchable TFT array with 5.5 cm² V⁻¹ s⁻¹ average mobility.

## Abstract

The development of intrinsically stretchable thin‐film transistors (TFTs) with high mobility is essential for next‐generation deformable electronics, including wearable displays and bio‐integrated systems. However, most approaches to improve stretchability in polymer semiconductors compromise charge transport due to disrupted molecular ordering. Here, we report a systematic exploration of wide‐range of alkyl bridge length variations of donor–acceptor‐type conjugated polymers to control crystallinity and morphology without altering the polymer backbone. We also propose a method to quantify the relative degree of crystallinity, enabling comparison across different polymer systems. When blended with an elastomer and aligned via solution shearing, the optimized polymer exhibited a maximum mobility of 6.4 cm2 V−1 s−1 at 0% strain (V
DS = −40 V). The polymer stretchable device maintained measurable mobility (0.6 cm2 V−1 s−1) at 100% strain under the perpendicular to the channel direction under a low V
DS of −10 V. Furthermore, wafer‐scale photopatterning enabled fabrication of a 38‐device intrinsically stretchable TFT array with high uniformity and an average mobility of 5.5 cm2 V−1 s−1 at 0% strain. This work establishes a molecular design framework that elucidates the link between structure, mechanical resilience, and electrical performance, offering generalizable principles and a scalable platform for high‐performance deformable electronics.

A side‐chain engineering strategy enables polymer semiconductors to achieve record‐high mobility and mechanical resilience in intrinsically stretchable transistors. By correlating crystallinity with charge transport and stretchability, this work establishes a predictive design rule. The resulting polymer/elastomer composites support wafer‐scale device fabrication, offering a scalable platform for next‐generation deformable electronics.