The effects of side-chain length and shape at C-9 position of polyfluorenes on the photoluminescence spectra and the fluorescence lifetimes are investigated for blue light-emitting poly(n-vinylcarbazole)/polyfluorene blends. As the side-chain length of alkylsubstituted polyfluorenes and of bulky cyclohexyl-substituted polyfluorenes increases, the fluorescence lifetime of the blends increase from 1 to 10 ns and the portion of PVK component contributing to the fluorescence lifetime of the blends increases. However, PL intensity of the blend decreases. This provides the side-chain length and shape of polyfluorene could affect the efficiency of energy transfer. (C) 2004 Elsevier B.V. All rights reserved.