Abstract
A white organic light-emitting diode (WOLED) is produced upon systematic introduction of deep-blue fluorescence from 4,4(')-bis(9-ethyl-3-carbazovinylene)-1,1(')-biphenyl to broad-band yellow phosphorescence from bis[3,5-bis(2-pyridyl)-1,2,4-triazolato]platinum(II) in the common host 4,4(')-bis(carbazol-9-yl)biphenyl. The carrier recombination zone is first identified upon investigating alternative device structures, then optimized by varying the thickness of the electron-transport layer. The WOLED exhibits striking stability of color and efficiency, as manifest by parameters at high brightness of 1000 cd/m(2) sustaining 94%-122% their values at 50 cd/m(2).