The control of the position of the energy levels in conducting polymers through fluorine substitution is demonstrated. The synthesis of four different monomers and polymers of the poly(terphenylenevinylene) type is presented. The synthetic procedure started with 4-bromo-2,5-dioctylphenylboronic acid (1) coupled by the Suzuki method with 4-bromobenzaldehyde to give 4'-bromo-2',5'-dioctyl-4-formylbiphenyl (2) that was again coupled by the Suzuki method with 4-diethylphosphonylmethylphenylboronic acid and 4-cyanomethylphenylboronic acid to give the monomers 4"-diethylphosphonylmethyl-2',5'-dioetyl-4-formylterphenyl (3) and 4"-cyanomethyl-2',5'-dioctyl-4-formylterphenyl (4). The partially fluorinated analogous monomers were prepared similarly employing 2,5-difluoro-3,6-diperfluorooctyl-1,4-dibromobenzene. This gave 4-bromo-2,5-difluoro-3,6-diperfluorooetyl-4'-diethylphosphonylmethylbiphenyl (5) and 4-bromo-2,5-difluoro-3,6-diperfluorooctyl-4'-cyanomethylbiphenyl (6). Compounds 5 and 6 were both subjected to Suzuki couplings with 4-formylphenylboronic acid to give respectively 4-formyl-2',5'-difluoro-3',6'-diperfluorooctyl-4"-diethylphosphonylmethylterphenyl (7) and 4-formyl-2',5'-difluoro-3',6'-diperfluorooetyl-4"-cyanomethylterphenyl (8). The monomers 3, 4, 7, and 8 were polymerized to give the polymers poly(2',5'-dioetyl-4,4"-terphenylenevinylene) (9), poly(2',5'-dioctyl-4,4"-terphenylenecyanovinylene) (10), poly(2',5'-difluoro-3',6'-diperfluorooctyl-4,4"-terphenylenevinylene) (11), and poly(2',5'-difluoro-3',6'-diperfluorooctyl-4,4"-terphenylenecyanovinylene) (12). Thin films of the polymers on polycrystalline gold substrates were subjected to ultraviolet photoelectron spectroscopy, and the ionization potentials were determined to be 4.85, 4.60, 4.75, and 5.95 eV for 9, 10, 11, and 12 respectively. The positions of the highest occupied energy levels were determined to be 1.45, 2.65, 2.25, and 3.05 eV lower than that of gold for 9, 10, 11, and 12, respectively. Fluorine and cyano substitution thus allows for an energy level tuning by as much as 1.6 eV.