White electroluminescence from polyfluorenes copolymerized with carbazole derivatives of Nile Red and 1,8-naphthalimide

Seven polyfluorenes containing new carbazole derivatives of Nile Red dye and 1,8-naphthalimide in the chain (obtained by the Suzuki and Yamamoto coupling) are characterized by the Nile Red emission band being less intense in their electroluminescence spectra than in photoluminescence spectra. In the optimal composition, 0.15 mol% fraction of Nile Red and 0.5 mol% fraction of N-[6-(2,7-dibromocarbazol-9-yl)hexyl]-4-diethylamino-1,8-naphthalimide provide a nearly white light electroluminescence (CIE coordinates x = 0.28; y = 0.36) with the brightness of 3278 cd m^–2 and the current efficiency of 1.86 cd A^–1.