Photonic Crystal Substrate for OLED Light Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing OLED devices suffer from low external efficiency due to trapped light, with current methods like diffraction gratings and surface plasmon coupling being impractical for commercial manufacturing, especially for bottom-emitting OLEDs.
Innovation Solution
Incorporating a photonic crystal structure on the substrate using high and low refractive index materials, deposited via liquid phase processes, to enhance light outcoupling by reducing total internal reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If diffraction gratings or surface plasmon coupling structures are used to improve light outcoupling, then light extraction efficiency is improved, but manufacturing complexity and compatibility with commercial OLED processes deteriorates
Solution Approach 1:
The patent changes the structural parameters of the substrate by introducing photonic crystal patterns (periodic variations in refractive index) rather than using conventional diffraction gratings. This parameter change enables effective light outcoupling while maintaining compatibility with standard OLED manufacturing processes, as the photonic crystal structure can be integrated into the substrate fabrication stage.
Solution Approach 2:
The patent uses photonic crystal patterns that can be replicated through standard photolithography and patterning techniques already employed in OLED manufacturing. By copying existing manufacturing methods rather than introducing new complex processes like shadow masks or specialized grating fabrication, the solution maintains ease of manufacture while achieving improved light extraction.
2Loss of energy
If photoresist-based plasmon inducing gratings are created, then light output efficiency is improved, but electrical connectivity of ITO conductors deteriorates due to insulating photoresist isolation
Solution Approach 1:
The patent extracts the light outcoupling function from the photoresist layer and transfers it to the substrate structure itself. By removing the photoresist after patterning the substrate, the insulating material that would isolate conductors is eliminated, while the photonic crystal pattern remains in the substrate to provide continuous light extraction functionality without compromising electrical connectivity.
Solution Approach 2:
The substrate acts as an intermediary structure that provides both mechanical support and optical functionality. The photonic crystal pattern in the substrate mediates between the need for light outcoupling and electrical connectivity, allowing light extraction without requiring insulating photoresist layers that would isolate conductors.
3Loss of energy
If shadow masks are used to create gratings, then light outcoupling is improved, but manufacturing complexity increases due to small grating dimensions
Solution Approach 1:
The patent performs the grating pattern creation during the substrate fabrication stage, before OLED assembly. By preliminarily patterning the substrate with photonic crystal structures using standard photolithography, the complex small-dimension grating fabrication is simplified into a preliminary substrate preparation step that uses existing manufacturing capabilities rather than requiring specialized shadow mask techniques.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The photonic crystal structure effectively extracts trapped light, improving the external efficiency of OLED devices and aligning with commercial manufacturing requirements.
Implementation Method 1
enhance light outcoupling by reducing total internal reflection
Implementation Method 2
Incorporating a photonic crystal structure on the substrate using high and low refractive index materials
Data Source
AI summary
The invention is based on the idea of providing a light emitting diode (OLED) device which contains a substrate with a photonic crystal, whereby the formed film structure induces enhancement of the liberation of photons trapped inside the light emitting device structure. The photonic crystal structure is a film structure on a substrate produced using a combination of high and low refractive index materials, at least one of the materials being based on a liquid phase deposited metal-oxide or metalloid oxide material. By means of the invention light trapped due to total internal reflection in a waveguide acting light emitting structure can be extracted efficiently from the device by introducing the photonic crystal device structure between the substrate and conductive anode layer.