Diketo‐Pyrrolo Pyrrole‐Based Acceptor‐Acceptor Copolymers with Deep HOMO and LUMO Levels Absorbing in the Near Infrared

Abstract

A series of acceptor‐acceptor (A‐A’) alternated copolymers based on dithienodiketo-pyrrolo pyrrole were synthesized by copolymerizing it with itself and other different electron‐poor monomers. The experimental and computed optoelectronic properties of four DPP‐based copoly-mers, P(DPP‐DPP) (with linear and branched chains), copolymer with diazapentalene P(DPP‐DAP) and also with dioxothienopyrrolebenzodifurandione P(DPP‐BTPBF), as well as thermal characteri-zations were described. UV‐visible spectrophotometry and cyclic voltammetry were used to esti-mate the optical and electrochemical bandgaps, and were found as very small: 1.3, 1.0, and 0.9 eV for P(DPP‐DPP), P(DPP‐DAP), and P(DPP‐BTPBF), respectively. The BTPBF unit allowed a strong reduction of the bandgap, leading to a broad absorption in the visible and near infra‐red regions from 650 to 1450 nm. These results were compared to analogous donor‐acceptor (D‐A) copolymers previously reported, in which DPP is replaced by DTS, P(DTS‐DPP), P(DTS‐DAP), and P(DTS‐ BTPBF). The same trend was observed. By comparing A‐A’ to D‐A’ copolymers analogues, it was shown that the bandgap remained the same while both HOMO and LUMO levels were lowered by roughly 0.2 eV.