The method of making a pyrrolo bisthiazole homopolymer starts with dissolving a dibrominated pyrrolo[3,2-d:4,5-d′]bisthiazole monomer having the formula:
where R is an alkyl group, in anhydrous tetrahydrofuran (THF). Then, the solvated monomer is treated with 1 equivalent of a Turbo-Grignard reagent complex having the formula iPrMgCl.LiCl at 0° C. to form a reaction mixture. The reaction mixture is stirred for 1 hour at room temperature, and after stirring, the reaction mixture is refluxed for 24 hours. A conjugated homopolymer product having the formula:
where n is the number of repeating units of pyrrolo[3,2-d:4,5-d′]bisthiazole, is recovered from the reaction mixture. The PBTz-based homopolymers showed broad absorption from 450 to 850 nm in thin film and excellent photochemical and thermal stability, making the polymers suitable for lightweight, low cost plastic electronic devices.