Spectroscopic and photoconductive properties of polymers containing trans-1,2-bis(9-carbazolyl)cyclobutane units sensitized by 2,4,7-trinitrofluorenone

A number of polymers containing trans-1,2-bis(9-carbazolyl)cyclobutane (DCzB) were examined for their photoconductivity in the presence of 2,4,7-trinitrofluorenone (TNF) and the results were correlated with the photophysical properties (excimer formation, energy migration, fluorescence quantum yield and fluorescence lifetime). Excimer formation by DCzB groups is sterically hindered whereas energy migration occurs efficiently in the DCzB polymers. Also, charge-transfer interaction with TNF is stronger for the DCzB polymers than for poly(9-vinylcarbazole) (PVCz). Photoconductivity of the DCzB polymers was better than that of PVCz when the charge-transfer band of the TNF-carbazole pair was irradiated, which agreed well with the photophysical observation. Although carrier generation and carrier transport processes could not be separately discussed at the moment, DCzB was shown to be a promising chromophore for photoconductive polymers.