Organic Light-Emitting Display Layered Structure for Uniform Thickness
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Solution Overview
Problem
In organic light-emitting display apparatuses, the non-uniform thickness of the intermediate layer leads to degradation in long-term reliability, causing stains and varying current densities across different locations.
Innovation Solution
The implementation of a layered structure comprising a first functional layer with a convex upper surface and a second functional layer with a planarized surface, both having hole injection functions, where the second layer's bottom surface is concave and its thickness increases towards the insulating layer, with distinct molecular weights and potentially different materials, and specific drying conditions to achieve uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an intermediate layer is formed using inkjet printing or nozzle printing, then the emission layer can be deposited on the pixel electrode, but the thickness of the intermediate layer becomes non-uniform causing stains and varying current densities
Solution Approach 1:
The intermediate layer is divided into multiple sub-layers (first intermediate layer, second intermediate layer, third intermediate layer) with different thicknesses and positions. Each sub-layer is formed separately through multiple printing processes, allowing precise control over the overall thickness profile and eliminating non-uniformity while maintaining ease of manufacture.
Solution Approach 2:
Different regions of the intermediate layer are given different local properties through the multi-sub-layer structure. The first, second, and third intermediate layers have varying thicknesses and positions to locally compensate for non-uniformity, ensuring uniform overall thickness while maintaining the ease of inkjet printing formation method.
2Reliability
If the intermediate layer thickness is made uniform, then long-term reliability is improved, but the manufacturing process becomes more complex
Solution Approach 1:
Rather than using a single complex process to achieve uniform thickness, the intermediate layer is segmented into multiple simpler sub-layers formed by sequential inkjet printing. This segmentation achieves uniformity through multiple simple steps rather than one complex process, maintaining reliability while avoiding excessive complexity.
Solution Approach 2:
The thickness parameter of the intermediate layer is changed across different sub-layers (first, second, and third intermediate layers have different thicknesses). By strategically varying the thickness parameter in each sub-layer, uniform overall thickness is achieved without requiring a single complex manufacturing process, thus improving reliability without significantly increasing device complexity.
Data Source
AI summary
An organic light-emitting display apparatus includes a pixel electrode above a substrate, an insulating layer covering an edge of the pixel electrode and including an opening exposing a central portion of the pixel electrode, a first functional layer disposed on the pixel electrode exposed by the opening and including a convex upper surface, a second functional layer disposed on the first functional layer and including a planarized upper surface, an organic emission layer disposed on the second functional layer, and an opposite electrode disposed on the organic emission layer.