Efficient Large-Area Transparent OLEDs Based on a Laminated Top Electrode with an Embedded Auxiliary Mesh

Abstract

To realize transparent organic light-emitting diodes (OLEDs), a top electrode should have excellent optical, electrical, and mechanical properties. Conventionally, transparent conductive oxides and semitransparent metal have been widely used for transparent top electrodes, but they have several fundamental We herein drawbacks. report efficient large-area inverted transparent OLEDs using a vacuum laminated top electrode with an embedded metal mesh. The laminated device with 1 mm pitch exhibits superior optical properties including a high transmittance of 75.9% at 550 nm, a low reflectance of 12.0% at 550 nm, and spectrally flat characteristics over the entire visible region and shows nearly ideal Lambertian angular emission characteristics with little angular color shift in both directions. Moreover, the lowered sheet resistance of 4 Omega/sq originating from the embedded metal mesh (1 mm pitch) led to efficient and uniform emission characteristics. As a result, the device shows a relatively high maximum current efficiency of 50.3 cd/A (bottom: 24.5 cd/A; top: 25.8 cd/A) and a maximum external quantum efficiency of 15.3% (bottom: 7.9%; top: 7.4%), which surpasses all previously reported values based on a laminated top electrode. In addition, we successfully demonstrate its potential as a large-area transparent top electrode in various optoelectronic devices through a large-area transparent OLED segment panel (45 X 90 mm(2), diagonal length of 70.2 mm in the active area) with a laminated top electrode.