Display Unit Charge Injection-Transport Layer Current Leakage
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Solution Overview
Problem
In organic electroluminescence (EL) displays, reducing current leakage between pixels is challenging, especially when a common light-emitting layer is used across all pixels, as finer pixel pitches make color coding of light-emitting layers more difficult, leading to increased current leakage and reduced light emission efficiency.
Innovation Solution
A display unit configuration that includes a plurality of first electrodes, an insulating layer with an opening and overhang facing each electrode, a charge injection-transport layer cut or with higher resistance at the overhang, and a common organic layer with a light-emitting layer shared across all pixels, where the layers are disposed in a specific order from the substrate side, effectively blocking current leakage between adjacent pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a common light-emitting layer is used across all pixels to simplify manufacturing, then manufacturing precision is improved, but current leakage between adjacent pixels increases
Solution Approach 1:
The charge injection-transport layer is segmented into discrete regions corresponding to each pixel by forming it to be cut or having higher resistance at the overhang portions of the insulating layer. This segmentation electrically isolates adjacent pixels while maintaining a common light-emitting layer structure across all pixels, thereby preventing current leakage between pixels without compromising manufacturing simplicity.
Solution Approach 2:
The charge injection-transport layer exhibits different electrical properties at different locations: it has charge injection and transport properties over the pixel areas, but is cut or has higher resistance at the overhang portions between pixels. This local variation in electrical properties allows the layer to simultaneously support common light emission across all pixels while blocking current leakage at pixel boundaries.
2Measurement precision
If the pixel pitch is reduced to enhance resolution, then measurement precision is improved, but the difficulty of forming color-coded light-emitting layers increases
Solution Approach 1:
The patent merges the light-emitting layer formation process for all pixels into a single common layer structure, eliminating the need for separate color-coded light-emitting layers in each pixel. This is combined with the use of color filters and the segmented charge injection-transport layer to achieve high resolution while simplifying the manufacturing process and avoiding the precision challenges of forming fine color-coded patterns.
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 current leakage, enhances charge injection efficiency, and improves light emission efficiency by electrically blocking the charge injection-transport layer at pixel boundaries, thereby minimizing color mixing and maintaining high luminance.
Implementation Method 1
a charge injection-transport layer being cut or having higher resistance at the overhang of the insulating layer to exhibit one or both of a charge injection property and a charge transport property
Implementation Method 2
an organic electroluminescence device provided with an insulating film as a device isolation film
Data Source
AI summary
A display unit includes a plurality of first electrodes provided to respective pixels; an insulating layer having an opening facing each of the first electrodes and having an overhang at an edge of the opening; a charge injection-transport layer being cut or having higher resistance at the overhang of the insulating layer to exhibit one or both of a charge injection property and a charge transport property; an organic layer including one light-emitting layer or a plurality of light-emitting layers common to all of the pixels; and a second electrode formed on an entire surface of the organic layer, the first electrodes, the insulating layer, the charge injection-transport layer, the organic layer, and the second electrode being disposed in this order from a substrate side.