Organic EL Light Extraction Structure Inclined Angles
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Solution Overview
Problem
Existing organic electroluminescent (EL) elements face reduced emission intensity due to trapped guided wave light from total internal reflection, and previous solutions either fail to improve front-direction emission intensity or increase the degradation rate by reducing the light-emitting region size.
Innovation Solution
An organic EL element with a light extraction structure having inclined portions on the reflective electrode, where the inclination angles are between 23° and 33°, and the structure is designed to surround the light-emitting region, allowing for efficient extraction of guided wave light in the front direction without reducing the light-emitting region size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If spherical lenses are formed on the substrate to extract guided wave light, then light extraction efficiency to the outside is improved, but emission intensity in the front direction does not improve significantly
Solution Approach 1:
The invention divides the light extraction function into two distinct components: spherical lenses on the substrate for general light extraction, and a separate light extraction structure with inclined portions on the reflective electrode for front-direction light extraction. This segmentation allows each component to optimize for its specific function, resolving the contradiction between overall light extraction efficiency and front-direction emission intensity.
Solution Approach 2:
The light extraction structure with inclined portions acts as an intermediary element between the reflective electrode and the organic EL layer. It mediates the extraction of guided wave light by changing the light propagation angle through its inclined surfaces (23°-33°), enabling front-direction extraction without compromising the light-emitting region size.
2Illumination intensity
If the light-emitting region size is reduced to increase front-direction emission intensity, then emission intensity is improved, but the degradation rate increases
Solution Approach 1:
Instead of increasing front-direction emission intensity by reducing the light-emitting region size (one-dimensional approach), the invention introduces a new dimensional element: the light extraction structure with inclined portions on the reflective electrode. This three-dimensional structure redirects guided wave light at specific angles (23°-33°), achieving front-direction intensity enhancement without compromising the light-emitting region area, thus maintaining reliability.
3Illumination intensity
If a light extraction structure with inclined portions is provided on the reflective electrode, then guided wave light is extracted in the front direction, but device complexity increases
Solution Approach 1:
The invention merges the light extraction structure with the reflective electrode into a single integrated component. The inclined portions are formed directly on the reflective electrode surface, combining the reflection function and the light extraction function into one element. This merging approach reduces device complexity compared to having separate components, while still achieving effective front-direction light extraction.
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
This configuration significantly increases the emission intensity in the front direction by effectively extracting guided wave light, enhancing light extraction efficiency while maintaining the size of the light-emitting region.
Implementation Method 1
A known method increases the emission intensity of an organic EL element by extracting guided wave light trapped in the organic EL element, due to total internal reflection, among light emitted from a light-emitting layer of the organic EL element.
Data Source
AI summary
Provided is an organic electroluminescent element that achieves increased emission intensity in the front direction of the organic electroluminescent element without reducing the size of the light-emitting region thereof. The organic electroluminescent element includes: a reflective electrode; an organic electroluminescent layer including a light-emitting layer; a transparent electrode; and a light extraction structure between the reflective electrode and the organic electroluminescent layer, the structure being of a protruding shape having inclined portions whose widths gradually narrow from the reflective electrode toward a light extraction side, in which: the light extraction structure is provided on the reflective electrode to surround a light-emitting region; in a cross section taken along a plane perpendicular to the reflective electrode where an angle of an inclination angle formed between the reflective electrode and each of the inclined portions is largest, the angle of the inclination angle is 23° or more to 33° or less.