Highly Efficient Color Stable Inverted White Top‐Emitting OLEDs with Ultra‐Thin Wetting Layer Top Electrodes

In addition, these approaches attempt to compensate drawbacks introduced by a non-optimized semitransparent top contact without enhancing the optical properties of the contact itself. Here, we focus on improving the characteristics of the top electrode by employing a multi-layer thin fi lm metal electrode comprising an ultra-thin MoO 3 ‐Au wetting layer system below the actual Ag electrode. Compared to conventional, thicker metal top contacts, these electrodes feature considerably increased transmittance, while providing a comparable sheet resistance thus achieving a performance similar to ITO bottom contacts. In the past, multi-layer electrodes based on thick metal layers have already shown potential for electrode optimizations in non-inverted OLEDs. [ 10,15 ] To demonstrate the full potential of our wetting layer metal electrode system in terms of optical and electrical properties, it has been integrated into an inverted tandem white top-emitting OLED stack that provides high external quantum effi ciency (EQE). Especially for display applications, the use of such inverted stacks is often favorable due to the preferred use of n-doped silicon in the backplane electronics. The bottom-emitting reference OLEDs are based on the same stack but in noninverted geometry. This structure represents a highly effi cient, state-of-the-art OLED layout. [ 16,17 ]