Organic EL Element Conductive Layer Luminance Uniformity
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Solution Overview
Problem
Existing organic electroluminescence elements face issues with luminance unevenness due to higher sheet resistance of anodes compared to cathodes, leading to in-plane unevenness and reduced external quantum efficiency, particularly when using ITO films as anodes.
Innovation Solution
The organic electroluminescence element incorporates a second electrode with opening parts to allow light transmission and an electrically conductive layer that is electrically connected to the light-emitting layer, reducing resistivity and improving carrier injection properties, while optionally including a conductive polymer layer or electron blocking layer to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If an ITO film is used as the anode to enable light transmission, then light transmissivity is improved, but sheet resistance increases leading to luminance unevenness
Solution Approach 1:
The anode is segmented into a transparent electrode layer (ITO) and a separate conductive layer patterned in a grid or mesh structure. This segmentation allows the transparent electrode to provide light transmission while the conductive layer provides low-resistance electrical connection, resolving the contradiction between light transmissivity and luminance uniformity.
Solution Approach 2:
The anode is constructed as a composite structure combining ITO (for transparency) with a conductive material layer (for low resistance). This composite approach allows both light transmission and low sheet resistance to be achieved simultaneously, eliminating luminance unevenness while maintaining high light transmissivity.
2Reliability
If the anode sheet resistance is reduced to improve luminance uniformity, then luminance unevenness is reduced, but carrier injection efficiency deteriorates
Solution Approach 1:
The conductive layer is strategically positioned and patterned to provide localized low-resistance pathways at the interface with the light-emitting layer, where carrier injection occurs. This local optimization of electrical conductivity improves carrier injection efficiency without requiring the entire anode to have low sheet resistance, thus maintaining luminance uniformity.
3Productivity
If a grid electrode structure with openings is used to improve carrier injection, then carrier injection is improved, but light transmission area is reduced
Solution Approach 1:
The conductive layer is arranged in a three-dimensional configuration with multiple layers and vertical connections, rather than a simple planar grid. This dimensional approach allows sufficient carrier injection pathways while minimizing the projected area blocking light transmission, resolving the contradiction between carrier injection efficiency and light transmission area.
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 reduces luminance unevenness and enhances carrier injection efficiency, improving external quantum efficiency and extending the element's lifespan by minimizing current crowding and reflection losses.
Implementation Method 1
a light-emitting layer configured to emit light when a predetermined voltage is applied between the first electrode layer and the second electrode layer
Implementation Method 2
The electrically conductive layer is configured to allow the light to pass therethrough
Data Source
AI summary
The organic electroluminescence element in accordance with the present invention includes: a light-emitting layer; a first electrode layer disposed on a first surface in a thickness direction of the light-emitting layer; a second electrode layer disposed on a second surface in the thickness direction of the light-emitting layer; and an electrically conductive layer. The light-emitting layer is configured to emit light when a predetermined voltage is applied between the first electrode layer and the second electrode layer. The second electrode layer includes an electrode part covering the second surface and an opening part formed in the electrode part to expose the second surface. The electrically conductive layer is configured to allow the light to pass therethrough, and is formed on an exposed region of the second surface exposed through the opening part in such a way as to be electrically connected to the electrode part and the light-emitting layer.