Diaza-substituted fluorenes having enhanced electron transporting ability as the efficient light emitter for highly efficient non-doped blue organic light-emitting diodes

Three fluorene compounds bearing donor (diphenylamino) and acceptor (diphenylvinyl) substituted were synthesized and characterized for highly efficient non-dopant organic light-emitting diodes. By incorporating diaza structural moiety into the fluorene derivative, such new fluorene materials enable highly efficient (up to 4.9% external quantum efficiency) and bright (over 60000 cd/m(2) electro-luminance) green-blue (CIE, x = 0.15, y = 0.36) organic light-emitting diodes (OLEDs). Through the comparison of hole-only and electron-only OLEDs, we have demonstrated that such high performance OLED is due to the diaza electron-deficient structural moiety that greatly improves the electron transportation and hence the efficiency of the devices.