Abstract: The geometries of the oligomers of(3,9-carbazole)n(n=1,2,3,4,6,8) were fully optimized with the density functional theory/B3LYP . On the basis of the optimized geometries, we calculated the ionization potentials(IP), electron affinities(EA) and other related energies . And we also obtained the absorption spectra using time-dependent density functional theory(TD-DFT) and ZINDO. The properties of poly(3,9-carbazole) were extrapolated by the relationships between the properties of oligomers and the polymerizing chain length n. The results above are studied comparing to those of poly(2,7-carbazole) and similar polymers. The analysis results indicate that the conjugations of poly(3,9-carbazole) are destroyed partly and absorption spectra blue-shift. In addition, the IP value of poly(3,9-carbazole) was similar to that of polyfluorene and thus the poly(3,9-carbazole) can be used as hole transport materials in multilayer electroluminescent devices. Finally we calculated the excited geometries of carbazole and its dimmer by CIS/6-31G and the emission spectra by TD-DFT and ZINDO.

Key words: Carbazole, Density functional theory, Absorption spectrum, Fluorescence property