High light extraction performance using evanescent waves for top emission OLED applications with thin film...

Area of Science:

• Optoelectronics
• Materials Science

Background:

• Top-emission OLEDs (TEOLEDs) suffer from light trapping due to refractive index mismatches in encapsulation layers.
• Waveguide mode loss is a significant factor limiting light extraction efficiency in TEOLED devices.

Purpose of the Study:

• To improve light extraction efficiency in TEOLEDs by minimizing waveguide mode loss.
• To develop a novel thin-film encapsulation (TFE) structure for enhanced light extraction using evanescent waves.

Main Methods:

• Fabrication of a novel TFE structure incorporating a low refractive index (RI) layer between the capping layer (CPL) and aluminum oxide (Al2O3).
• Utilizing evanescent waves to redirect internally reflected light.
• Implementing atomic layer deposition for TFE processing.

Main Results:

• The novel TFE structure (CPL/ low RI layer/ Al2O3/ polymer/ Al2O3) significantly reduces waveguide mode loss.
• Light extraction is enhanced due to the redirection of light by evanescent waves and the electric field in the low RI layer.
• A 23% increase in current efficiency and a 26% enhancement in blue index were achieved for a blue TEOLED device.

Conclusions:

• The developed TFE structure effectively improves light extraction in TEOLEDs.
• The integration of evanescent waves in encapsulation offers a promising strategy for optoelectronic device enhancement.
• This approach is applicable to future encapsulation technologies for flexible optoelectronic devices.