OLED Capping Layer Optical Thickness Control
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Solution Overview
Problem
Existing OLED displays face challenges in achieving high luminous efficiency and minimizing color shift when viewed from different angles due to the capping layer's optical thickness and composition, which affects the emission layer's performance.
Innovation Solution
The OLED display's capping layer optical thickness is controlled, and the emission layer is structured with a combination of host and dopant in one portion and only host in another, optimizing the luminous efficiency and viewing angle by adjusting the thickness and refractive index of the capping layer within specific ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the optical thickness of the capping layer is increased to improve luminous efficiency, then luminous efficiency is improved, but color shift associated with viewing angle increases
Solution Approach 1:
The patent optimizes the optical thickness of the capping layer within a specific range (about 110 nm to about 140 nm) to balance luminous efficiency and viewing angle performance. By precisely controlling this parameter, the invention achieves high luminous efficiency while minimizing color shift when viewed from different angles.
Solution Approach 2:
The emission layer is structured with different compositions in different portions: a first portion contains both host and dopant materials, while a second portion contains only host material. This local differentiation allows the device to achieve high luminous efficiency in the doped region while maintaining good viewing angle characteristics in the undoped region.
2Loss of energy
If the optical thickness of the capping layer is optimized for luminous efficiency, then luminous efficiency is improved, but strong resonance occurs generating color shift
Solution Approach 1:
The patent identifies and implements an optimal optical thickness range for the capping layer (about 110 nm to about 140 nm) that avoids strong resonance conditions. This parameter optimization ensures high luminous efficiency is achieved without triggering the harmful resonance effects that cause color shift.
Solution Approach 2:
By creating regions with different dopant concentrations in the emission layer, the invention locally manages resonance effects. The undoped or lightly-doped regions help suppress strong resonance that would otherwise cause color shift, while still allowing the doped regions to provide high luminous 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
This approach enhances luminous efficiency and reduces color shift, improving the display's performance by optimizing the capping layer's thickness and emission layer structure, thereby enhancing the viewing experience across various angles.
Implementation Method 1
The electrons injected from one electrode and holes injected from the other electrode may be combined in the organic emission layer to generate excitons. Light may be emitted as the excitons release energy, when the excitons change from an excited state to a ground state.
Implementation Method 2
luminous efficiency of light emitted from the organic emission layer may be affected by the capping layer. However, as luminous efficiency increases, strong resonance may occur, which may generate color shift associated with a viewing angle.
Data Source
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AI summary
An organic light emitting diode (OLED) display includes a substrate, a first electrode disposed on the substrate, an organic emission layer disposed on the first electrode, a second electrode disposed on the organic emission layer, and a capping layer disposed on the second electrode, in which an optical thickness of the capping layer is in a range of about 110 nm (1100 Å) to about 140 nm (1400 Å).