Theoretical studies on the ground state and excited state of poly (3,9-carbazole)

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 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.