Electromagnetic Mode Management in Transparent DMD Electrodes for High Angular Color Stability in White OLEDs

The understanding and management of the optical behavior of dielectric/metal/dielectric (DMD)-based electrodes are crucial for the design of fully transparent OLEDs. Specifically, the chromatic stability with the viewing angle of white OLED emission remains an important issue due to the angle dependence of internal reflection at the organic/electrode interface as the wavelength varies. The purpose of the present work is to provide a complete analysis of the optical behavior of DMD structures by Variable Angle Spectroscopic Ellipsometry in order to optimize the transmittance of DMD-based transparent white OLEDs over a wide viewing angle. The analysis of the optical modes contributing to power dissipation reveals that the reduction of plasmonic and waveguided modes is related to the antireflection properties of the DMD electrode. This results in a simultaneous significant improvement in the absolute value of the transmittance across the full visible spectral range and in the color stability of white OLED emission over a wide viewing cone of 120°, thus paving the way for a new generation of transparent white lighting sources.