Conjugation-break spacers in semiconducting polymers: Impact on polymer processability and charge transport properties

Conjugation-break spacers (CBSs) are intentionally introduced into the diketopyrrolopyrrole (DPP)-based polymer backbones. We reveal that the solution processability progressively increases with the percentage of CBSs, while charge mobility inversely varies to the CBS ratio. For instance, the polymer DPP-30 with solubility of ∼10 mg/mL in dichlorobenzene provides an average mobility over 1.4 cm² V^-1 s^-1, while DPP-0 exhibits an average mobility of 4.3 cm² V^-1 s^-1 with solubility of ∼3 mg/mL. This correlation provides a general guidance to design polymers with desired electronic performance and solution processability for large-scale roll-to-roll processing. Most encouraging, DPP-70 can be melt processed in air and provide hole mobilities up to 0.30 cm² V^-1s^-1, substantially higher value than their solution-processed counterparts about 0.1 cm² V^-1 s^-1. The mobility boost in melt-processed devices, together with completely eliminating the need to use toxic solvent in the processing, encourages to design melt-processable polymers for electronic devices.