Enhancing the Light Extraction Efficiency in Micro‐Organic Light‐Emitting Diodes with Metalens

Due to the total internal reflection caused by the mismatch of the refractive indices between organic layers and oxide layers within an organic light‐emitting diode (OLED), most of the light energy is trapped inside the device; if the size of an OLED is further limited to a few micrometers, most of the light will be lost on the side wall, which will further reduce the light outcoupling efficiency. Herein, the mechanism of the light extraction efficiency of micro‐OLEDs with metalens is studied. The results show that the metalens has a better optical extraction efficiency for single‐reflection light rather than requiring light to be multireflected by the conventional photonic structures. As a result, it effectively improves the light‐emitting coupling efficiency and even the OLED size shrinks to 1 μm. This technique is expected to boost the efficiency in ultrahigh‐pixel‐density microdisplays required in emerging augmented reality (AR)/virtual reality (VR) and is extrapolated to other light‐emitting devices such as quantum‐dot light‐emitting diodes (QLEDs), micro‐light‐emitting diodes (μLEDs), and perovskite light‐emitting diodes (PeLEDs).