Abstract: A library of π-conjugated systems have been developed through conventional tools of coupling (e.g. Suzuki coupling, Stille coupling) and have been used for the fabrication of organic optoelectronic devices. Herein, a facile, atom-efficient and environmentally benign pathway is outlined, with water as the only by-product, for the synthesis of conjugated Schiff-based copolymers based on sulfur-heterocycle fused naphthalene diimides (NDIs) and aromatic diamines. These copolymers showed broad absorption spectra in the ultraviolet-visible (UV-Vis) region and low-lying LUMO levels at about −4.07—−4.19 eV. The relationship between the chemical structure and the performance, including the optical properties, electrochemical properties, thermal stability, morphologies and the field-effect performance in transistors, is fully studied using these polymers as active layer. Compared with P1 and P2 , P3 exhibits an absorption peak at 754 nm, with red shifts of 76 nm and 75 nm, respectively. An electron mobility of up to 2.47×10⁻³ cm²/ (V·s) can be achieved for P3 -based transistors after performing a thermal annealing process at 300 ℃. The incorporation of rigid structure units into polymer conjugated skeleton can effectively tune its spectral absorption, energy level structure as well as the film morphology, thus improving the device performance.