Branched polythiophene as a new amorphous semiconducting polymer for an organic field-effect transistor

We have designed and synthesized new polymer semiconductors containing branched oligothiophene units. These polymers form amorphous films with high thermal stability owing to strong interactions between oligothiophene side chains. On thin-film devices fabricated by spin coating of these polymers as a semiconducting layer, the field-effect mobility increased from 10−6 to 10−4 cm2 V−1 s−1 with increasing side-chain length. The UV–vis absorption, photoluminescence and electrochemical properties of the polymers in solutions were also affected by the length of the side chains