Enhanced device efficiency in organic light-emitting diodes by dual oxide buffer layer

We have demonstrated an improvement in device performance of fluorescent organic light-emitting diodes (OLEDs) by inserting a dual anode buffer layer composed of tungsten oxide (WO3) and molybdenum oxide (MoO3). The advantage of adding dual anode buffer layers with different deposition sequences over individual and composite oxide buffer layers has been systematically analyzed based on their electronic and optical properties. The incorporation of single and composite buffer layers has been revealed to induce a very low injection barrier for holes in tri-layer fluorescent OLEDs which results in a charge imbalance in the emission layer. In contrast, a proper sequence of buffer layers (WO3/MoO3) exhibiting higher contact angle (lower surface energy) and higher surface roughness, together with a step-wise increment of potential barrier leads to a better overall charge balance in the active emission layer. Therefore, an enhanced current efficiency and power efficiency of similar to 5.8 cd/A and similar to 5.2 lm/W respectively were recorded for the WO3/MoO3 buffer unit, which was better than the insertion of individual and composite layers.