Imparting Stretchable Semiconducting Polymers with Ambipolar Charge-Transport Capability by Using a Lewis Base of Triazabicyclodecene

Stretchable devices have attracted attention in recent years owing to the rapid development of wearable electronics. However, extensive procedures and structural optimization are often required to synthesize strain-insensitive polymers with a satisfactory charge transport performance. In addition, the ambipolar transport of transistors enables more fascinating and compact electronics. We hereby mix diketopyrrolopyrrole-alt-bithiophene (DPP2T) and isoindigo-alt-bithiophene (IID2T) units in the forms of block copolymer (BCP), random copolymer (RP), and polymer blend (PB), and adopt a Lewis base of triazabicyclodecene (TBD) as an additive to impart ambipolar charge transport and intrinsic stretchability. Accordingly, BCP shows the best morphological and energy level compatibility with TBD, indicating the most effective dopant accommodability. In addition, the physically order-disrupting nature of additives enables BCP and RP to strengthen the local aggregation and facilitate charge transport. Under the stretched state, the incorporated TBD proves its ability to delay the crack-onset strain and increase the dichroic ratio and crystallinity of the polymer films. Under 100% strain, the TBD-doped BCP retains 30% mobility, outperforming that of <10% retention in RP and PB. Moreover, under the cyclic stretch-release test, the TBD-doped BCP preserved 65% mobility after 800 cycles, which surpassed that of the pristine BCP, which has only 14% retention. Our work presents a methodology for optimizing the dopant accommodability of conjugated polymers to improve their stretchability and charge transport performance simultaneously. Moreover, such simple utilization for device optimization is surely impactful for developing soft electronics.