Side Chain Engineering: Achieving Stretch-Induced Molecular Orientation and Enhanced Mobility in Polymer Semiconductors

Abstract

Polymer semiconductors have been widely studied as an important component of stretchable electronic devices. However, most stretchable polymer semiconductors suffer from different degrees of charge mobility degradation at high strain. Here, we report a novel side chain engineering strategy to realize stretch-induced enhancement of molecular orientation and charge transport in donor–acceptor conjugated polymers. Specifically, hybrid siloxane-based side chains wifth different silicon chain lengths were grafted onto a backbone of poly-diketo-pyrrolopyrrole-selenophene (PTDPPSe). The charge mobility can be enhanced with an appropriate increase of the silicon chain length. Most importantly, increasing the silicon chain length resulted in significant improvement of stretchability, including decreasing elastic modulus and increasing fracture strain. Interestingly, charge mobilities parallel to the stretching direction for PTDPPSe-4Si, PTDPPSe-5Si, and PTDPPSe-6Si are all above 1 cm2 V–1 s–1 at 100% strain, higher than those of their unstretched states. This enhanced charge mobility is attributed to the excellent ductility and high strain-induced alignment of polymer chains. The current study is expected to provide guidance for the design of intrinsically stretchable polymer semiconductors and advance the development of wearable electronics.