A functional organic-inorganic composite containing carbazole moieties (electron donors) and TiO2 (electron acceptors) in different molar ratios, TiO2-modified poly(N-vinylcarbazole) (PVK-TiO2), was synthesized through a nucleophilic reaction. The molecular and electronic structure of the PVK-TiO2 composite was characterized with Fourier transform infrared, ultraviolet-visible absorption, cyclic voltammetry, and so forth. The highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels of the PVK-TiO2 composite were higher than those of pristine poly(N-vinylcarbazole). The PVK-TiO2 composite exhibited an enhanced glass-transition temperature and improved thermal stability. The photoinduced charge transfer observed in photofluorescence and photoconductivity measurements makes applications in the field of photodetectors possible. The PVK-TiO2 composite containing carbazole moieties and TiO2 in a molar ratio of about 58 : 1 was found to have the best photosensitivity. (C) 2008 Wiley Periodicals, Inc.