OLED Surface Modification Layer for Light Extraction
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Solution Overview
Problem
Conventional OLEDs suffer from significant light loss due to the optical waveguide effect, with about 80% of visible light being trapped within the device, and existing methods to enhance light extraction are complex, costly, and environmentally unfriendly.
Innovation Solution
A light-emitting device with a surface modification layer having a non-planar surface, formed by a multilayer structure with differing coefficients of expansion, which reduces the optical waveguide effect and increases light emission by forming a buckled or wrinkled surface for the subsequent layers, thereby decreasing light trapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional coating and patterning methods are used to increase surface roughness, then light extraction is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent changes the physical-chemical parameters of the encapsulation layer by selecting materials with specific thermal expansion coefficients. The encapsulation layer material is chosen to have a thermal expansion coefficient that differs from both the substrate and the emission layer, enabling spontaneous buckling and non-planar surface formation through thermal stress during curing or temperature changes, thereby improving light extraction without complex manufacturing steps
Solution Approach 2:
The system utilizes self-organizing spontaneous buckling of the encapsulation layer due to differential thermal expansion. This self-service mechanism automatically creates the desired non-planar surface morphology without requiring external intervention, complex patterning processes, or additional manufacturing steps, thus reducing manufacturing complexity while achieving improved light extraction
2Loss of energy
If chemical etching or physical etching is used to increase surface roughness, then light extraction is improved, but environmental harm and manufacturing cost increase
Solution Approach 1:
The patent converts the potentially harmful thermal expansion mismatch into a beneficial self-organizing buckling mechanism. Instead of using harmful chemical etchants or mechanical abrasion, the differential thermal expansion between layers is harnessed to spontaneously create the desired surface roughness, eliminating environmental harm while achieving improved light extraction
Solution Approach 2:
The patent replaces mechanical and chemical etching systems with a thermal-mechanical self-organizing system. The mechanical buckling is driven by thermal stress during curing or temperature changes, substituting harmful chemical and mechanical processes with a cleaner thermal field approach that achieves the same light extraction improvement without environmental harm
3Loss of energy
If surface roughness is increased through conventional methods, then light extraction is improved, but production time increases
Solution Approach 1:
The patent merges the encapsulation layer formation process with the light extraction enhancement function. The encapsulation layer, which is necessary for device protection and sealing, is simultaneously designed to have differential thermal expansion properties that cause spontaneous buckling. This merging of functions eliminates separate etching or patterning steps, reducing production time while achieving improved light extraction
Solution Approach 2:
The patent incorporates the light extraction enhancement feature into the encapsulation layer deposition and curing process itself. By selecting materials with appropriate thermal expansion coefficients, the buckling and non-planar surface formation occur automatically during the encapsulation layer curing or subsequent temperature changes, before final device assembly. This preliminary action eliminates the need for subsequent separate processing steps, thereby increasing manufacturing throughput
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 light extraction from OLEDs by reducing the optical waveguide effect, simplifying the manufacturing process, and lowering production costs while minimizing environmental impact.
Implementation Method 1
a significant amount of light generated by the active stack is lost due to the optical waveguide effect created by the refractive index differences between the various layers of the OLED
Implementation Method 2
formed by a multilayer structure with differing coefficients of expansion, which reduces the optical waveguide effect and increases light emission by forming a buckled or wrinkled surface
Data Source
Figure 1~2
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AI summary
An organic light emitting diode (10) includes a substrate (12) having a first surface (14) and a second surface (16), a first electrode (32), and a second electrode (38). An emissive layer (36) is located between the first electrode (32) and the second electrode (38). The organic light emitting diode (10) further includes a surface modification layer (18). The surface modification layer (18) includes a non-planar surface (30, 52).