Symmetrically functionalized diketopyrrolopyrrole with alkylated thiophene moiety: from synthesis to electronic devices applications

Abstract

A symmetrically conjugated molecular semiconductor derived from diketopyrrolopyrrole (DPP), i.e., 2,5-dihexadecyl-3,6-bis(5-(3-hexylthiophen-2-yl)thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione [DPP(3HT) (2) ], has been synthesized using the Stille coupling reaction. The optical band gap of DPP(3HT) (2) is found to be 1.65 eV with HOMO energy level of -5.13 eV. DPP(3HT) (2) is thermally stable up to 348 A degrees C exhibiting only 5 % weight loss. X-ray diffraction analysis revealed the DPP(3HT) (2) to be polycrystalline with a high degree of crystallinity. It showed highly narrow and strong diffraction peaks with a d-spacing of ca. 30.18 (at 2 theta = 2.09A degrees, full width at half maximum: 2 theta = 0.126A degrees) indicating an end-to-end packing distance with the long alkyl chains (along the a-axis) being slightly tilted and partially interdigitated for effective packing. Field-effect transistors and complementary inverters employing DPP(3HT) (2) as a p-channel semiconductor have been fabricated and characterized.