Hyperbranched organic-inorganic hybrid conjugated polymers P1 and P2 were prepared via FeCl3-oxiditive polymerization of 4,7-bis(3-ethylhexyl-2thienyl)-2,1,3-benzothiadiazole (A) and octa(3-ethylhexyl-2-thienyl-phenyl)polyhedral oligomeric silsesquioxane (POSS) (B) at different POSS concentrations. Compared to linear polymer PM derived from A, P1, and P2 exhibit much higher PL quantum efficiency (Phi(PL-f)) in condensed state with improved thermal stability. Phi(PL-f) of P1 and P2 increased by 80% and 400%, and the thermal degradation temperatures of P1 and P2 are increased by 35 degrees C and 46 degrees C, respectively. Light-emitting diodes were fabricated using P1, P2, and PM. While the electroluminescent spectra of both P1 and PM show lambda(max) at 660 nm, P1 exhibits a much narrower EL spectrum and higher electroluminescence (similar to 500%) compared with PM at a same voltage and film thickness. The maximum current efficiency of P1 is more than seven times of that of PM. The turn-on voltages of the LEDs are in the order of P2 > PM > P1. LED prepared by blending P1 with MEH-PPV shows a maximum luminescence of 2.6 x 10(3) cd/m(2) and a current efficiency of 1.40 cd/A, which are more than twice (1.1 x 10(3) cd/m(2)) and five times (0.27 cd/A) of LED of PM/MEH-PPV blend, respectively. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5661-5670, 2009