Tuning the Mobility of Indacenodithiophene-Based Conjugated Polymers via Coplanar Backbone Engineering

Conjugated polymers based on indacenodithiophene-benzothiadiazole (IDT-BT) have attracted great interest due to their high charge carrier mobilities while being low crystallinity (i.e., near-amorphous). They represent a promising design strategy to achieve both excellent stretchability and electrical performance. Here, we describe an approach to structural modifications of IDT-BT, namely, by introducing noncovalent interactions and substituting building blocks to promote extended coplanar backbones. We systematically investigated the effects of structural modifications on backbone conformation, polymer aggregations, and charge carrier mobilities. Among the investigated polymers, the fluorinated derivative IDT-FBT demonstrated the highest charge carrier mobility of 5.19 cm²/(V·s), along with low activation energy and Urbach energy, indicating its low energy disorder level. The high mobility was attributed to the higher backbone planarity reinforced by S···F and H···F noncovalent interactions and improved interchain interactions through strong aggregation. Our findings indicate that increasing backbone coplanarity may further improve mobility in low-crystallinity conjugated polymers.