Abstract: In order to investigate the effect of substituents on the two-photon absorption properties(TPA), the one- and two-photon absorption properties were theoretically studied by using ZINDO/SOS method. The results indicate that the compounds based on DTT exhibit strong TPA. Comparing to the unsubstituent molecule, it was found that bis-acceptor substituted molecules possess of drastic enhancement of the TPA cross section at the shorter wavelength absorption peaks and bis-donor substituent can increase the TPA cross section at the longer wavelength absorption peaks.

Key words: Two-photon absorption cross section, Chromophores based on dithienothiophene, Sum-Over-States(SOS)