Impact of π-Conjugated Linkers on the Effective Exciton Binding Energy of Diketopyrrolopyrrole-Dithienopyrrole Copolymers.

The effect of the nature of the π-conjugated linker that is positioned between electron-deficient 2,5-dihydropyrrolo[3,4-]pyrrole-1,4-dione (DPP) and electron-rich dithieno[3,2-:2',3'-]pyrrole (DTP) units in alternating DPP-DTP copolymers on the optical and electrochemical band gaps and the effective exciton binding energy is investigated for six different aromatic linkers. The optical band gap is related to the electron-donating properties of DTP and the electron-withdrawing properties of DPP but likewise strongly affected by the nature of the linker and varies between 1.13 and 1.