A randomly nano-structured scattering layer for transparent organic light emitting diodes

Area of Science:

• Optoelectronics
• Materials Science

Background:

• Transparent organic light-emitting diodes (TOLEDs) face challenges with light confinement within the device structure.
• Efficiently extracting light is crucial for improving the performance of TOLEDs.

Purpose of the Study:

• To introduce and demonstrate a random scattering layer (RSL) as an effective internal light-extracting layer for TOLEDs.
• To enhance the external quantum efficiency (EQE) and luminous efficacy (LE) of TOLEDs.

Main Methods:

• Fabrication of a random scattering layer (RSL) comprising a random nano-structure (RNS) and a high refractive index planarization layer (HRI PL).
• Integration of the RSL into transparent organic light-emitting diodes (TOLEDs).
• Characterization of optical and electrical properties, including EQE, LE, transmittance, and viewing angle dependency.

Main Results:

• A significant enhancement of 40% in EQE and 46% in LE was achieved with the RSL.
• No deterioration in transmittance was observed.
• Reduced viewing angle dependency of electroluminescence (EL) spectra.

Conclusions:

• The RSL effectively extracts confined waveguide modes from the indium tin oxide (ITO)/OLED stack.
• The scattering effect of the RSL plays a dominant role in light extraction.
• The RSL is a promising technology for widespread application in TOLEDs, improving performance without spectral changes.