Theoretical insights on the high and differential charge transfer performance of dithienyl-diketopyrrolopyrrole-based polymers as ambipolar semiconductors

Abstract

Diketopyrrolopyrrole (DPP)-containing polymers are among the highest mobility semiconductors for field-effect transistor applications. The molecular geometries, electronic structures and charge transport properties as ambipolar organic semiconductors of two series of total 24 donor–acceptor dithienyl-diketopyrrolopyrrole-based oligomers mDTDPPAr and nBDTDPPAr (m = 1–4, n = 1–2, Ar = TT, BT, BDT, TVT) are investigated theoretically through density functional theory and classical Marcus charge transfer theory. The effects of oligomer length form = 1–4, different Ar groups, and different Ar position on the structures and charge transfer properties are systematically studied. It was found that expanding π-conjugate backbone is a viable method to improve their semiconductor performance. Oligomers 4DTDPPTT, 4DTDPPBT, 4DTDPPTVT possess prominent ambipolar semiconductors properties with charge transfer mobilities of 9.62, 10.73, 12.60 cm2 V−1 s−1 for hole and of 7.54, 8.06, 15.56 cm2 V−1 s−1 for electron, respectively. 4DTDPPBDT exhibits large but unbalanced ambipolar performance with hole/electron transfer mobilities of 10.86/20.17 cm2 V−1 s−1 due to the special conjugation of BDT. Changing the order and position of donor and acceptor units has less significant influence on charge transfer mobility. Anisotropic mobilities are also studied to clarify the different charge transfer directions.