Composite Substrate Refractive Index Matching for OLED Light Extraction
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Solution Overview
Problem
Conventional OLED devices face inefficiencies in light extraction due to refractive index differences between substrates and ITO films, leading to high reflectance and poor light extraction efficiency.
Innovation Solution
A composite substrate is created by bonding a glass sheet with a refractive index of 1.55 to 2.3 and a resin sheet with a refractive index of 1.55 to 2.3, optimizing their refractive indices to reduce reflectance at interfaces and enhance light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional substrate with refractive index of about 1.5 is used, then the structure is simple and easy to manufacture, but the reflectance at the interface between substrate and ITO film is high, leading to poor light extraction efficiency
Solution Approach 1:
The patent uses a composite substrate consisting of a glass sheet and a resin sheet bonded together. The glass sheet has a refractive index of 1.8 to 2.2 and the resin sheet has a refractive index of 1.4 to 1.6, creating a gradient refractive index structure that reduces reflection at interfaces while maintaining manufacturability through lamination of two separate materials.
Solution Approach 2:
The patent applies different refractive index properties to different parts of the substrate structure. The glass sheet portion has high refractive index (1.8-2.2) to match ITO and reduce reflection at that interface, while the resin sheet portion has low refractive index (1.4-1.6) to reduce reflection at the air interface, optimizing light extraction at each boundary locally.
2Loss of energy
If a high-refractive-index glass substrate is used to extract light, then the reflectance at the interface between substrate and ITO film is reduced, but the reflectance at the interface between substrate and air increases, resulting in poor light extraction
Solution Approach 1:
The patent employs a composite structure where a high-refractive-index glass sheet (1.8-2.2) is bonded to a low-refractive-index resin sheet (1.4-1.6). This composite design allows the glass side to minimize reflection with ITO while the resin side minimizes reflection with air, solving the contradictory reflection issues at the two different interfaces simultaneously.
Solution Approach 2:
The patent changes the refractive index parameter across the substrate structure by combining materials with different refractive indices. The glass sheet provides high refractive index (1.8-2.2) for ITO interface optimization, while the resin sheet provides low refractive index (1.4-1.6) for air interface optimization, creating a parameter gradient that reduces reflection at both boundaries.
3Loss of energy
If the refractive index of the glass sheet is increased to reduce reflectance, then light extraction efficiency improves, but the scattering of glass shards increases when the glass breaks
Solution Approach 1:
The patent combines a high-refractive-index glass sheet with a low-refractive-index resin sheet. The resin sheet acts as a protective layer that contains and suppresses the scattering of glass shards when the glass breaks, while the high refractive index of the glass maintains good light extraction efficiency.
Solution Approach 2:
The resin sheet serves as an intermediary protective layer between the glass sheet and the external environment. When the glass breaks, the resin contains the glass shards and prevents their scattering, while still allowing the optical function of the high-refractive-index glass to operate effectively for 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
The composite substrate effectively suppresses light reflection, improving light extraction efficiency and preventing scattering of glass shards, thereby enhancing the performance of OLED devices.
Implementation Method 1
the glass sheet has a refractive index nd of 1.55 or more and 2.3 or less and the resin sheet has a refractive index nd of 1.55 or more and 2.3 or less
Data Source
AI summary
Provided is a composite substrate, including a glass sheet and a resin sheet bonded to each other, in which the glass sheet has a refractive index nd of 1.55 or more and 2.3 or less and the resin sheet has a refractive index nd of 1.55 or more and 2.3 or less.