Mingliang Sun

Efficient white-light-emitting diodes based on polyfluorene doped with fluorescent chromophores

Orange-red emitting small molecule chromorephores, 4,7-di-2-thienyl-2,1,3-benzothiadiazole, 4,7-(2′-diselenophenyl)-2,1,3-benzothiadiazole, and 4,7-bis(N-methylpyrrol-2-yl)-2,1,3-benzo-thiadiazole were synthesized and used for fabrication of fluorescent white-emitting device with polyfluorene (PFO) as host by solution processing. By careful controlling of dopant concentration, balanced narrow band-gap (NGB) electroluminescence (EL) emission can be obtained by solution processing due to the incomplete energy transfer from PFO to narrow band gap molecules. EL spectra of the obtained devices were very stable at a wide range of operating voltage. The best white-emitting device reached luminous efficiency of 7.54cd∕A with the CIE coordinates (0.33, 0.34) at luminance over 1000cd∕m2.