OLED Lens Outcoupling Efficiency Refraction
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Solution Overview
Problem
The outcoupling efficiency of light in OLED displays is reduced due to total reflection of light inside the device caused by differences in refractive index between the cathode and the structure, leading to trapped light.
Innovation Solution
Incorporating a lens on the first passivation layer corresponding to the emission portion of the organic light emitting diode, with a cover layer and a second passivation layer to refract and extract light, improving the outcoupling efficiency by changing the light path and reducing light loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflective electrode and transmissive electrode are used in top emission OLED display, then light can be reflected and emitted, but light is totally reflected inside the device due to refractive index difference, reducing outcoupling efficiency
Solution Approach 1:
A lens structure is introduced as an intermediary element between the emission layer and the external environment. The lens has a refractive index that is higher than the surrounding medium, creating a refractive index gradient that gradually bends light rays and enables them to escape the device. This intermediary structure mediates the transition of light from the high refractive index region (emission layer) to the low refractive index region (external environment), resolving the total internal reflection problem.
Solution Approach 2:
The patent changes the refractive index parameter by introducing a lens structure with a specific refractive index profile. The lens creates a continuous or stepped variation in refractive index from the emission layer outward, transforming the light propagation conditions. This parameter change allows light to gradually change direction and escape the device rather than being totally reflected, thereby improving outcoupling efficiency while maintaining light emission.
2Productivity
If light is emitted from the emission layer, then the OLED display functions, but light is trapped inside the device due to total reflection, reducing efficiency
Solution Approach 1:
The lens structure employs curved surfaces with specific radii of curvature to refract light rays. The curved geometry of the lens creates a gradient in the light path, allowing rays emitted at various angles to be gradually bent toward the normal direction and escape the device. This curvature-based approach transforms the linear light propagation into a curved path that overcomes the total internal reflection barrier, improving light extraction efficiency.
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 solution effectively increases the outcoupling efficiency of light by refracting and extracting light emitted from the emission layer, as demonstrated by improved emission intensity compared to OLED displays without the lens configuration.
Implementation Method 1
at least one lens positioned on the first passivation layer, the at least one lens disposed in a position corresponding to the emission portion of the organic light emitting diode
Data Source
AI summary
A display device for improving an outcoupling efficiency of emitted light is disclosed. The display device includes a substrate, a subpixel arranged on the substrate, the subpixel including an organic light emitting diode having an emission portion that emits light, a first passivation layer disposed on the organic light emitting diode, at least one lens positioned on the first passivation layer, the at least one lens disposed in a position corresponding to the emission portion of the organic light emitting diode, a cover layer covering the at least one lens, and a second passivation layer disposed on the cover layer. A refractive index of the at least one lens is greater than a refractive index of the cover layer.