Effects of a 2 nm thick Al_2O_3 buffer layer in metal auxiliary electrode on lifetime and stable operation of large-area organic light emitting diodes

摘要

We have investigated the buffer layer effect in the auxiliary electrode on the lifetime and stable operation of large-area organic light-emitting diodes (OLEDs). A 2-nm-thick Al_2O_3 layer was introduced between the Mo and Al in a conventional Mo-Al-Mo metal auxiliary electrode structure. The structure of the buffer layer inserted auxiliary electrode is MO-Al-Al_2O_3-Al-Al_2O_3-Al-MO. By introducing the 2-nm-thick Al_2O_3 buffer layers, the etch rate of the Al layer was effectively controlled, which can prevent the formation of undercut structures in the metal auxiliary electrode caused by the different etch rates of Mo and Al. A trapezoidal etch profile was obtained from the Al_2O_3 buffer layer inserted metal auxiliary electrode structure; the profile did not contain undercuts or voids. The buffer layer inserted auxiliary electrode was used when fabricating a 30 × 120 mm~2 green emission OLED lighting panel. The lifetime of the OLEDs devices with buffer layer introduced metal auxiliary electrode reached 40,000 h for the LT 70 condition, which is around four times longer than that obtained from OLEDs without the buffer layers.