Blend engineering with graft copolymer elastomers for simultaneous realization of extraordinary stretchability and n-type charge transport

As a key component for stretchable electronics, polymer semiconductors become increasingly important due to the large-area printing, high-density device manufacturing as well as versatile chemical functionalization. However, stretchable n-type polymers lag far behind p-type counterparts, suffering poor stability, low performance and limited candidates. Herein, we demonstrate for the first time a graft copolymer blending strategy to achieve a highly stretchable n-type semiconducting film with a crack-onset strain exceeding 300% and stable electrical characteristics under deformation. Blending with the graft copolymer results in effective suppression of hole carrier transport in the bipolar semiconductor while maintaining electron mobility comparable to that of the neat film. The polymer semiconductor and graft copolymer elastomer form a two-phase horizontal separation microstructure, wherein the well-interconnected semiconductor-rich microdomains are encompassed in the elastomer phase, ensuring excellent mechanical stretchability without sacrificing carrier mobility. Remarkably, the blend films with the graft copolymer form two-dimensional chain alignment under strains from 0% to 150%, demonstrating stable charge transport in both stretching directions. In addition, there is no degradation in the electrical characteristics during 1000 stretching-releasing cycles for the blend films with the graft copolymer. This work provides an effective approach for blend engineering toward the development of n-type highly stretchable semiconductors.