Extremely Efficient Transparent Flexible Organic Light‐Emitting Diodes with Nanostructured Composite Electrodes

Abstract Transparent flexible organic light‐emitting diodes (TF‐OLEDs) are emerging as a leading technique in bendable display and curved lighting applications due to their merits including superior mechanical flexibility, low power consumption, and broad color gamut. However, it is challenging to turn TF‐OLEDs into a power‐efficient large‐area light source. Here, an improved TF‐OLED structure on a plastic substrate that achieves a device transparency over 70% and extremely efficient warm‐white emission from both sides is reported. The key feature of this device structure is the combination of transparent metal–dielectric composite electrodes, which are patterned with moth‐eye nanostructures for broadband and angle‐independent light outcoupling. By collectively reducing ohmic losses and releasing the trapped photons, the TF‐OLEDs achieve a record external quantum efficiency of 72.4% and power efficiency of 168.5 lm W⁻¹ with a color‐rendering index over 84. These results present the great potential of TF‐OLEDs for use in a wide variety of flexible applications.