Donor–Acceptor Conjugated Polymers Based on Indacenodithiophene Derivative Bridged Diketopyrrolopyrroles: Synthesis and Semiconducting Properties

Abstract

Two indacenodithiophene derivative bridged diketopyrrolopyrroles (DPP), i.e., 2,7-bis(2,5-bis(2-decyltetradecyl)-3,6-dioxo-4-(thiophen-2-yl)-2,3,5,6-tetrahydropyrrolo[3,4-c]pyrrol-1-yl)-s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-dione (DDPP-PhCO) and 2,2′-(2,7-bis(2,5-bis(2-decyltetradecyl)-3,6-dioxo-4-(thiophen-2-yl)-2,3,5,6-tetrahydropyrrolo[3,4-c]pyrrol-1-yl)-s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-diylidene)dimalononitrile (DDPP-PhCN), were developed via intramolecular Friedel–Crafts acylation and Knoevenagel condensation. A series of donor–acceptor (D–A) conjugated polymers were synthesized by Stille or direct arylation polycondensation with these two novel units as acceptors and vinyl or thiophene derivatives as donors. The polymers with DDPP-PhCO as acceptor unit exhibited optical bandgaps (Egopt) of ca. 1.2 eV and the highest occupied molecular orbital (HOMO) energy levels of ∼−5.3 eV with the difference less than 0.1 eV, and their lowest unoccupied molecular orbital (LUMO) levels were in the range o...