FORMATION AND GROWTH OF BLACK SPOTS IN ORGANIC LIGHT-EMITTING-DIODES

We report electroluminescence (EL) degradation studies of thin-film or ganic light-emitting diodes under ambient conditions. Bilayer organic ITO/TPD/Alq(3)/Mg/Ag devices were studied via EL and photoluminescence (PL) microscopy. In situ imaging of device luminescing areas and meas urement of sample luminance were performed, allowing for a detailed st udy of black spot formation and luminance reduction under constant vol tage stress conditions. Post-stress devices were further characterized using PL microscopy, and it was found that black spots result from de lamination of the metal at the Alq(3)/Mg interface initiated by pinhol es on the cathode, caused by substrate defects. (C) 1996 American Inst itute of Physics.