The electronic structures of polyindenoindenes (PInIn) and their derivatives have been studied by self-consistent-field crystal orbital method. The substituent effect is also discussed. The calculated results show that these polymers are semiconductors with low band gaps. In addition, although the band gap decreases for most of the substituted derivatives of polyindenoindenes, the polymers cannot be conductors in the intrinsic state by the substitution. Electron affinity of the substituted PInIns chain is raised due to the substitution of electron-withdrawing substituentes, while ionization potential is decrased for the electron- donating substituentes. Therefore, the substitution of electron-donating group is favorable for p-type doping, while the substitution of electron- withdrawing group for n-type doping.

Key words: INDENE P, MOLECULAR ORBITAL METHOD, SELF-CONSISTENT FIELD, ELECTRONIC STRUCTURE, SUBSTITUENT EFFECT