Influences of the Non‐Covalent Interaction Strength on Reaching High Solid‐State Order and Device Performance of a Low Bandgap Polymer with Axisymmetrical Structural Units

A high organic field-effect transistor mobility (0.29 cm2V−1s−1) and bulk-heterojunction polymer solar cell performance (PCE of 6.82%) have been achieved in a low bandgap alternating copolymer consisting of axisymmetrical structural units, 5,6-difluorobenzo-2,1,3-thiadiazole. Introducing the fluorine substituents enhanced intermolecular interaction and improved the solid-state order, which consequently resulted in the highest device performances among the 2,1,3-thiadiazole-quarterthiophene based alternating copolymers.