Organic dyes have been studied for applications in large-area, flexible, cheap, and efficient organic electronic devices. Among them, diketopyrrolopyrrole (DPP) has gained attention thanks to its planar structure, photochemical and thermal stability, and easy processability. Also, the electron-withdrawing nature of DPP makes its application attractive in the synthesis of donor-acceptor (D-A) copolymers, with appealing features such as the tunable energy levels and photophysical and electrochemical properties. Inspired by these exciting characteristics, a copolymer was developed based on DPP, thiophene, and fluorene (PFDPP2T). Photophysical and electrochemical studies using both experimental and theoretical approaches were performed aiming to understand the properties of this material, such as, for instance, the D-A characteristic and the outstanding electrochemical stability upon oxidation that enables more than 400 cycles of p-doping. The outcomes unveil fundamental aspects of this class of copolymers, reinforcing their suitability for photo-electrochemical and optoelectronic applications.