OLED Capping Layer High Refractive Index Light Extraction
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Solution Overview
Problem
Current organic light emitting diode (OLED) displays face challenges in light efficiency due to the need for additional backlights in passive display devices like LCDs and limitations such as slow response time and narrow viewing angles, necessitating improved light extraction methods.
Innovation Solution
The implementation of an OLED display with a capping layer made of inorganic materials having a high refractive index, combined with a thin film encapsulation layer and a low refractive layer, which are alternately stacked to enhance light extraction and efficiency, along with a resonant auxiliary layer to adjust light characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional OLED structure is used, then the device is simple and easy to manufacture, but light efficiency is insufficient
Solution Approach 1:
The capping layer is divided into multiple sub-layers with different refractive indices (first capping layer with refractive index 1.7-2.5, second capping layer with refractive index 2.5-6.0). This segmentation allows each layer to perform specific light extraction functions, improving overall light efficiency while maintaining manageable structural complexity
Solution Approach 2:
The patent uses composite material structure combining organic light emitting layer with inorganic capping layers of different refractive indices. This composite approach enables effective light extraction by utilizing the optical properties of different materials, resolving the contradiction between simplicity and light efficiency
2Use of energy by moving object
If LCD is used as display device, then backlight can be added to improve light efficiency, but response time becomes slow and viewing angle becomes narrow
Solution Approach 1:
The OLED display is designed as a self-emissive device that generates its own light through electroluminescence in the organic light emitting layer. The capping layers enhance this self-generated light extraction efficiency, eliminating the need for external backlights while maintaining fast response characteristics inherent to OLED technology
Solution Approach 2:
The patent changes the optical parameters (refractive indices) of the capping layers to optimize light extraction from the self-emissive OLED. By adjusting refractive index parameters of the capping layers, light efficiency is improved without compromising the fast response time and wide viewing angle advantages of self-emissive OLEDs
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 significantly improves light efficiency by amplifying light through resonance effects, enhancing viewing angles and response times, thereby overcoming the limitations of traditional OLED displays.
Implementation Method 1
a capping layer on the organic light emitting diode and including a high refractive layer including an inorganic material having a refractive index that is equal to or greater than about 1.7 and equal to or less than about 6.0
Implementation Method 2
This configuration significantly improves light efficiency by amplifying light through resonance effects
Data Source
AI summary
An organic light emitting diode display including: a substrate; an organic light emitting diode on the substrate; a capping layer on the organic light emitting diode and including a high refractive layer including an inorganic material having a refractive index that is equal to or greater than about 1.7 and equal to or less than about 6.0; and a thin film encapsulation layer covering the capping layer and the organic light emitting diode, the inorganic material including at least one selected from the group consisting of CuI, thallium iodide (TlI), BaS, Cu2O, CuO, BiI, WO3, TiO2, AgI, CdI2, HgI2, SnI2, PbI2, BiI3, ZnI2, MoO3, Ag2O, CdO, CoO, Pr2O3, SnS, PbS, CdS, CaS, ZnS, ZnTe, PbTe, CdTe, SnSe, PbSe, CdSe, AlAs, GaAs, InAs, GaP, InP, AlP, AlSb, GaSb, and InSb.