OLED Light Extraction Substructure with Discrete Waveguide Elements
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Solution Overview
Problem
A significant challenge in organic light emitting diodes (OLEDs) is the inefficiency in light extraction, with approximately 25% of generated light escaping, 45% trapped in the organic material, and 30% trapped in the glass layer, leading to suboptimal performance.
Innovation Solution
A light extraction substructure incorporating chemically strengthened glass with discrete waveguide elements and a light expulsion matrix is introduced, optimizing light coupling and expulsion by controlling refractive indices and geometries to enhance light extraction from the OLED device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional OLED structures are used, then the device is simple to manufacture, but light extraction efficiency is poor with only 25% of generated light escaping
Solution Approach 1:
The light extraction substructure is segmented into discrete waveguide elements (e.g., pillars, posts, or ridges) distributed across the glass substrate surface. Each waveguide element acts as an independent light extraction pathway, collectively improving overall light extraction efficiency while maintaining manufacturability through standard glass fabrication processes
Solution Approach 2:
The light extraction substructure with waveguide elements serves as an intermediary between the OLED stack and the external environment. It mediates light propagation by guiding trapped light modes toward extraction points, converting internally trapped light into extractable light paths without requiring changes to the OLED active layers
2Loss of energy
If light extraction substructure with waveguide elements is added, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The light extraction substructure creates a porous-like pattern of discrete waveguide elements on the glass substrate surface. This periodic structure provides multiple light extraction pathways while maintaining structural integrity and compatibility with standard glass manufacturing processes, balancing complexity with performance
Solution Approach 2:
The waveguide elements are designed with specific geometric parameters (height, width, spacing, and refractive index) that are optimized for light extraction. By controlling these parameters within certain ranges, the structure achieves high light extraction efficiency while remaining compatible with existing manufacturing capabilities
3Loss of energy
If discrete waveguide elements are distributed over waveguide surface, then light extraction is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The glass substrate with distributed waveguide elements can be manufactured using standard glass fabrication processes that self-organize the waveguide patterns. The manufacturing process inherently creates the required periodic structure through controlled glass forming techniques, reducing the need for post-processing and high-precision assembly steps
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 proposed solution significantly increases light extraction efficiency, improving the overall performance of OLEDs by reducing light entrapment within the glass layer and enhancing light expulsion, resulting in a substantial increase in emitted intensity.
Implementation Method 1
The index of refraction of the light expulsion matrix η(P) is at least 0.2 less than the effective index of refraction of the superstructure waveguide η eff (O) and the effective index of refraction of the discrete light extraction waveguide elements η eff (WG). In addition, the respective effective indices of refraction of the superstructure waveguide η eff (O) and the discrete light extraction waveguide elements η eff (WG) differ by 0.2 or less.
Implementation Method 2
The light expulsion matrix is distributed at varying thicknesses to enhance the planarity of a diode superstructure-engaging side of the light extraction substructure and to provide light expulsion sites at the waveguide element termination points of the discrete light extraction waveguide elements.
Data Source
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Figure 6A~6B
AI summary
An organic light emitting diode comprising a light extraction substructure and a diode superstructure is provided. The light extraction substructure comprises a light expulsion matrix distributed over discrete light extraction waveguide elements and a waveguide surface of the glass substrate. The light expulsion matrix is distributed at varying thicknesses to enhance the planarity of a diode superstructure-engaging side of the light extraction substructure and to provide light expulsion sites at the waveguide element termination points of the discrete light extraction waveguide elements. In operation, light originating in the organic light emitting semiconductor material of the diode superstructure is coupled to the discrete waveguide elements of the light extraction substructure as respective coupled modes characterized by an approximate coupling length defined as the propagation distance required for an optical mode to be coupled from the superstructure waveguide to one of the discrete waveguide elements of the light extraction substructure.