Two kinds of blue light-emitting hyperbranched crosslinkable polyfluorene PI and P2 with different contents of branch unit were synthesized via the palladium-catalyzed Suzuki coupling reaction, and the linear crosslinkable polyfluorene P0 was also prepared for comparison. The molecular weight and thermal behavior of the polymers were measured by GPC, DSC and TGA. Compared with uncrosslinked PO, P1 and P2, the photoluminescence spectra of crosslinked P0, P1 and P2 were little influenced. After annealing for 3 h at 200 degrees C in air, the photoluminescence spectrum of P2 with higher contents of branch unit showed more excellent stability compared with that of P1 and P0. The spectrum-stable hyperbranched polyfluorene can be used in multilayer and multicolor PLED. (c) 2007 Published by Elsevier Ltd.