Textured Glass Substrate for OLED Light Extraction
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Solution Overview
Problem
Current methods for enhancing light extraction in organic light-emitting diodes (OLEDs) face challenges such as high costs, complexity, and difficulty in scaling up due to issues like total internal reflection at the glass-air interface, which limits the external quantum efficiency to around 20%.
Innovation Solution
A textured glass substrate is created using an etching cream process that differentiates the surface roughness, reducing total internal reflection and enhancing light scattering, allowing for improved light extraction by tuning the microstructure of the glass surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional methods (sandblasting, scattering films, patterned electrodes, nano-structured layers, metal gratings, micro-lens arrays) are used to enhance light extraction, then light out-coupling efficiency is improved, but device complexity, manufacturing cost, and process difficulty increase
Solution Approach 1:
The invention changes the surface morphology parameter of the glass substrate by controlling the etching cream composition (fluorine content, pH value, temperature) and etching time to create specific micro-structures (roughness Ra=200-600 nm, feature size 2-20 μm) that enhance light extraction without adding complex components or multi-step processes
Solution Approach 2:
The invention extracts and removes the planar surface layer of the glass substrate through chemical etching to create a textured surface, eliminating the need for additional scattering films, micro-lens arrays, or patterned structures while achieving improved light out-coupling efficiency
2Loss of energy
If conventional methods are used to enhance light extraction, then light out-coupling efficiency is improved, but manufacturing cost and scalability are worsened
Solution Approach 1:
The glass substrate itself serves as the light extraction enhancement structure through self-etching, where the substrate's own surface is modified by the etching cream to create the desired micro-structure, eliminating the need for external scattering films, micro-lens arrays, or complex patterning equipment
Solution Approach 2:
The invention replaces mechanical/physical methods (sandblasting, micro-lens arrays, metal gratings) with a chemical etching process that is simpler to implement, more scalable, and can be performed on existing glass substrates without adding mechanical complexity or cost
3Loss of energy
If the glass substrate surface is roughened to reduce total internal reflection, then light extraction is improved, but substrate strength may be reduced
Solution Approach 1:
The invention optimizes the etching parameters (cream composition, temperature, time) to control the depth and extent of surface modification, creating sufficient roughness for light extraction while preserving the bulk mechanical strength of the glass substrate
Solution Approach 2:
The invention applies partial surface modification rather than complete removal or deep etching, modifying only the surface layer to the extent necessary for light extraction while maintaining the structural integrity and strength of the overall substrate
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 textured glass substrates increase external quantum efficiency by up to 1.8 times, achieving greater than 60% external quantum efficiency compared to planar substrates, while maintaining a low-cost and scalable process.
Implementation Method 1
The EC process has been applied for roughening the surface of glass based on the principle of differentiated etching
Implementation Method 2
which results in improved light scattering from the OLED by eliminating the total internal reflection (TIR) between the interface of ITO/glass and/or glass/air
Implementation Method 3
eliminating the total internal reflection (TIR) between the interface of ITO/glass and/or glass/air
Data Source
AI summary
A textured glass substrate along with articles comprising a textured glass substrate and methods of making are provided. The substrates retain the mechanical and optical properties of the untextured glass, while the process provides a reliable and low cost, easy scale up method. The resulting glass substrates are of particular use for light extraction in organic light emitting diode structures.