Asymmetric thiophene/pyridine flanked diketopyrrolopyrrole polymers for high performance polymer ambipolar field-effect transistors and solar cells. Issue 3 (23rd December 2016) - Qiu, Gege
Abstract : Two new asymmetric DPP polymers were designed and synthesized, which gave excellent ambipolar transporting properties for OFETs and PSCs. Abstract : Two novel asymmetric thiophene/pyridine flanked diketopyrrolopyrrole (DPP) based polymers, namedPPyTDPP-TT andPPyTDPP-BT were designed, synthesized and applied in organic field-effect transistors (OFETs) and polymer solar cells (PSCs). In contrast to the reported bipyridine flanked DPP, the asymmetric DPP polymers incorporating thiophene/pyridine flankers exhibited narrower bandgaps of ∼1.5 eV and deeper HOMO energy levels, thus leading to a broadened absorption from 500 to 850 nm and were potentially beneficial for low-energy photon harvesting. Both polymers displayed promising ambipolar semiconducting properties. The hole and electron mobilities ofPPyTDPP-TT reach 0.48 cm 2 V −1 s −1 and 0.18 cm 2 V −1 s −1 ; andPPyTDPP-BT reach 0.55 cm 2 V −1 s −1 and 0.08 cm 2 V −1 s −1, respectively. Intriguingly, due to their ambipolar properties, two polymers can play an ambipolar role, both as electron donors and acceptors with PC71 BM and P3HT in PSCs. Photovoltaic devices based onPPyTDPP-BT as the donor material reach PCEs of 7.56% and achieve 0.59% as the acceptor material, while those based onPPyTDPP-TT reach 5.48% with PC71 BM and 0.82% with P3HT, respectively. These results suggest that the adoption of asymmetric flanker DPP polymers can effectively tune the absorption properties of polymers as excellent ambipolar transporting polymers towards high performance in both OFETs and PSCs.