Optically Transparent Layer on Partially Transmitting Reflector for QLED Emission
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional light-emitting devices, such as OLED and QLED, face challenges in optimizing light extraction and emission while maintaining electronic properties and view angle control, as patterning functional layers for different pixel thicknesses is complex and costly, leading to conflicts between optical and electronic properties.
Innovation Solution
A layer structure is introduced with a substantially transparent region and a partially reflective layer on top of the functional charge transport and emissive layers, allowing for optimized light extraction and angular light profile without additional processing of the functional layers, using materials like SiO2 and ITO that are robust and easily processed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If different thicknesses of electron transport layers are used for each pixel to optimize light extraction, then light extraction efficiency is improved, but device complexity and manufacturing cost increase due to patterning requirements
Solution Approach 1:
The patent introduces an additional layer (optically transparent layer with partially transmitting reflector) on top of the existing device structure. This adds a new dimension to the device architecture, allowing optimization of light extraction through vertical cavity effects rather than through complex lateral patterning of functional layers. The additional layer provides wavelength-specific optical path length control without requiring modification of the underlying charge transport layers.
Solution Approach 2:
The optically transparent layer is segmented into different thicknesses for different color pixels (red, green, blue), with each segment optimized for its specific wavelength. This segmentation allows independent optimization of optical properties for each pixel type while maintaining a uniform device structure, avoiding the need to pattern the functional charge transport layers.
2Illumination intensity
If functional layers are patterned to achieve different pixel thicknesses, then optical properties are optimized, but electronic properties and view angle control are compromised
Solution Approach 1:
The patent segments the optically transparent layer into different thicknesses for different color pixels while keeping the underlying functional layers (charge transport layers, emissive layer) uniform and intact. This allows independent optimization of optical properties for each pixel without compromising the electronic properties of the functional layers, as the segmentation is applied only to the optically transparent layer added on top.
3Ease of manufacture
If conventional light-emitting device structures are used, then manufacturing is simpler, but light extraction and emission control are insufficient
Solution Approach 1:
The optically transparent layer with partially transmitting reflector is added as a preliminary structural element that enables enhanced light extraction and emission control. This additional layer is deposited using standard manufacturing techniques and can be patterned using conventional photolithography, maintaining manufacturing simplicity while significantly improving light emission performance through optical cavity effects.
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 solution enhances directional and on-axis light emission, allowing independent optimization of electrical and optical properties, reduces the complexity of patterning functional layers, and extends the lifetime of the device by protecting it from moisture and oxygen.
Implementation Method 1
By optimizing the thickness of the substantially transparent region, the light emitted in a particular direction can be maximized because the transparent region and partially reflective layer form a cavity effect
Implementation Method 2
a partially transmitting reflector layer disposed on the optically transparent layer
Data Source
AI summary
A light-emitting device for use in a display device has enhanced directional light emission, and enhanced on-axis light emission in particular. A light-emitting device includes a layer structure that includes from a non-emitting side: a first electrode layer; a first charge transport layer; an emissive layer; a second charge transport layer; a second electrode layer; an optically transparent layer; and a partially transmitting reflector layer. The light-emitting device comprises a plurality of regions and each region emits light of a different wavelength, such as for example red, green, and blue light-emitting regions. The optically transparent layer is present in at least one of the plurality of regions. The optically transparent layer may be present in more than one of the plurality of regions, and a thickness of the optically transparent layer may differ in different regions to optimize light emission at different wavelengths. The light-emitting device may include a scattering layer that scatters the emitted light, which may be switchable to permit different viewing angle display modes.