Investigation of Structure???Property Relationships in Diketopyrrolopyrrole-Based Polymer Semiconductors via Side-Chain Engineering

Systematic side-chain engineering has been performed for diketopyrrolopyrrole-selenophene vinylene selenophene (DPP-SVS) polymers to determine the optimal side-chain geometries for the most efficient charge transport, and the structure–property relationship has been thoroughly investigated using a range of analyses. A series of DPP-SVS polymers, ranging from 25-DPP-SVS to 32-DPP-SVS, with branched alkyl groups containing linear spacer groups from C2 to C9 has been synthesized, and the electrical performance of these polymers is significantly dependent on both the length of the spacer group and its odd–even characteristics. Spacer groups with even numbers of carbon atoms exhibit charge-carrier mobilities that are 1 order of magnitude higher than those with odd numbers of carbon atoms. The optimized charge transport has been obtained from 29-DPP-SVS with a C6 spacer, showing the maximum mobility of 13.9 cm2 V–1 s–1 (VGS, VDS = −100 V) and 17.8 cm2 V–1 s–1 (VGS, VDS = −150 V). Longer spacer groups deviate fr...