Question

Determining optimal crystallinity of diketopyrrolopyrrole-basedterpolymers for highly efficient polymer solar cells and transistors

Answer 1

A new series of conjugated random terpolymers (PDPP2T-Se-Th) was synthesized from an electron-deficient diketopyrrolopyrrole (DPP)-based unit in conjugation with two electron-rich selenophene (Se) and thiophene (Th) species, with a view to inducing different crystalline behaviors of the polymers. The crystallinity of the polymers can be systematically controlled by tuning the ratio between Se and Th; an increase in Se content induced a remarkable increase in the melting and crystallization temperatures as well as the crystallinity of the PDPP2T-Se-Th terpolymers. These changes in the crystalline properties of polymers had a dramatic effect on the performances of organic field-effect transistors (OFETs) and polymer solar cells (PSCs). However, their effect on each type of devices was very different. The charge carrier mobilities of the PDPP2T-Se-Th terpolymers in OFET devices increased remarkably as the Se content increased in the polymers, showing that PDPP2T-Se100 with Se/Th ratio = 100/0 had very high hole and electron mobilities (4.72 and 5.54 cm2 V–1 s–1, respectively) with well-balanced ambipolar property.