OLED Pixel Protective Layer Layout for Light Extraction
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Solution Overview
Problem
Existing display devices face challenges in achieving high-quality image display with high light extraction efficiency, high aperture ratio, high resolution, low cost, and high reliability, while also requiring a simple manufacturing process.
Innovation Solution
The display device incorporates a structure with first and second light-emitting elements separated by a protective layer and a gap, where the protective layer has a higher refractive index than the gap, and includes a microlens array to enhance light extraction and isolation between elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If light-emitting elements are arranged closely to increase aperture ratio, then aperture ratio is improved, but light extraction efficiency deteriorates due to light interference and reduced extraction area
Solution Approach 1:
A protective layer with higher refractive index than the gap material is introduced as an intermediary between adjacent light-emitting elements. This protective layer serves multiple functions: it prevents short circuits between elements, provides mechanical protection, and most importantly, its higher refractive index creates a greater refractive index difference with the gap material, enhancing light extraction efficiency at the interfaces while allowing closer spacing of elements to maintain high aperture ratio
2Reliability
If protective layers are added to protect light-emitting elements, then reliability is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The protective layer is designed to perform multiple functions simultaneously: electrical insulation between adjacent light-emitting elements, mechanical protection of the EL layers, and optical function through its higher refractive index to enhance light extraction. By combining these functions into a single layer rather than adding separate layers for each function, the structure remains relatively simple while achieving high reliability and improved light extraction efficiency
3Loss of energy
If gap material with low refractive index is used to improve light extraction, then light extraction efficiency is improved, but manufacturing precision requirements increase due to gap control
Solution Approach 1:
The invention changes the refractive index parameter of the protective layer to be higher than that of the gap material. This parameter change creates a stronger refractive index contrast that enhances light extraction efficiency. The gap can be filled with low-cost materials like air, nitrogen, or other gases, and the protective layer's higher refractive index compensates for any variability in gap dimensions, reducing the stringency of manufacturing precision requirements for gap control
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 results in a display device with improved light extraction efficiency, high aperture ratio, high resolution, and reliability, while being cost-effective and manufacturable through a simpler process.
Implementation Method 1
the protective layer has a higher refractive index than the gap
Implementation Method 2
light-emitting elements (also referred to as EL elements or EL devices) utilizing an electroluminescence (hereinafter referred to as EL) phenomenon
Data Source
AI summary
A display device capable of displaying high-quality images can be provided. A display device includes a first light-emitting element, a second light-emitting element, a first protective layer, a second protective layer, and a gap. The first light-emitting element includes a first lower electrode, a first EL layer over the first lower electrode, a first upper electrode over the first EL layer, and the second light-emitting element includes a second lower electrode, a second EL layer over the second lower electrode, and a second upper electrode over the second EL layer. The first light-emitting element and the second light-emitting element are adjacent to each other. The first protective layer is provided over the first light-emitting element and the second light-emitting element and includes a region in contact with the side surface of the first EL layer and the side surface of the second EL layer. The second protective layer is provided over the first protective layer. The gap is provided between the first EL layer and the second EL layer and is provided between the first protective layer and the second protective layer.