We report on hybrid light-emitting devices (HLEDs) based on CdSe/ZnS quantum dots in polymer matrices. Color purity of the HLED with a mixed matrix consisting of polyvinylcarbazole (PVK) and 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) improves with the increasing concentration of PBD. We attribute this improvement to the increased electron mobility of the matrix. By using an n-type cyano-containing polymer derived from 6-(3,6-dibromo-9H-carbazol-9-yl)hexanenitrile and tetraphenylsilane to replace PVK: PBD as the matrix, further pure red emission with Commission Internationale De L'Eclairage coordinates of (0.67, 0.33) and maximum external quantum efficiency of 2.51% has been achieved. (C) 2012 Elsevier B.V. All rights reserved.