An organic electroluminescent dot-matrix display using carbon underlayer

A carbon layer has been inserted between ITO and a hole-transport layer in an organic electroluminescent (EL) device with the aim of improving its stability and efficiency. The structure of the proposed device is ITO/carbon/hole-transporting material/Alq3 + dopant/cathode (Al-Li). The carbon layer is quite effective for improving the threshold voltage and the contrast. These advantages are explained in terms of ionization potentials, effectiveness in adhesion and its light absorption. By using the carbon layer, an EL display panel with 16 × 96 dots has been fabricated. The display exhibits excellent performance: a half decay period of 4000 h at an initial luminance of 500 cd cm−2 and strong and pure green emission. In addition, no dark spots are detectable during the operation.