Quantum Dot Display Optical Layer for Higher Light Extraction
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Solution Overview
Problem
Display devices using quantum dots for light conversion suffer from low directivity, leading to inefficiencies in light-extraction and power consumption, as a significant amount of converted light is emitted back to the light-emitting element rather than contributing to the display.
Innovation Solution
A display device structure incorporating a first and second light-emitting element, a wavelength-conversion layer, and an optically functional layer, where the wavelength-conversion layer is positioned between the light-emitting elements and the optically functional layer to enhance light extraction efficiency by transmitting the first light and reflecting the second light, with the optically functional layer having specific reflectance properties to optimize light transmission and reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If quantum dots are used for wavelength conversion, then color conversion efficiency is improved, but light-extraction efficiency deteriorates due to low directivity causing light to be emitted back to the light-emitting element
Solution Approach 1:
The patent introduces a microlens array layer that adds optical focusing functionality in the vertical dimension. Each microlens corresponds to a pixel and focuses light in the direction perpendicular to the display surface, converting the isotropic emission from quantum dots into directional light output, thereby improving light-extraction efficiency without compromising color conversion efficiency
Solution Approach 2:
The microlens array acts as an intermediary optical element between the quantum dot layer and the external environment. It receives light emitted in all directions from the quantum dots and redirects it toward the viewing direction, effectively mediating the transition from omnidirectional to directional emission and resolving the contradiction between conversion efficiency and extraction efficiency
2Loss of energy
If quantum dots emit light in all directions, then light conversion efficiency is improved, but power efficiency deteriorates due to significant light being emitted back to the light-emitting element
Solution Approach 1:
The patent converts the harmful back-emission of light toward the light-emitting element into useful light output. The microlens array captures light that would otherwise be wasted and redirects it toward the viewer, transforming energy loss into effective light output and thereby improving power efficiency while maintaining high conversion efficiency
3Loss of energy
If a simple wavelength-conversion layer is used, then device complexity is reduced, but light-extraction efficiency deteriorates due to lack of optical control
Solution Approach 1:
The patent segments the optical control function into discrete microlenses, each corresponding to a pixel. This segmentation allows independent optimization of light extraction for each pixel while maintaining overall system simplicity. The microlens array can be manufactured using standard photolithography techniques, balancing optical performance with manufacturing complexity
Solution Approach 2:
The microlens array layer serves multiple functions simultaneously: it focuses light to improve extraction efficiency, maintains color accuracy by preserving the spectral characteristics of quantum dot emission, and can be integrated with standard display manufacturing processes. This multi-functionality achieves high light-extraction efficiency without proportionally increasing device complexity
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 proposed structure significantly enhances light-extraction efficiency, reduces power consumption, and improves the quality of displayed images by effectively utilizing the converted light, resulting in a more reliable and power-efficient display device.
Implementation Method 1
The first light enters the wavelength-conversion layer and the wavelength-conversion layer has a function of emitting second light whose wavelength is longer than that of the first light
Implementation Method 2
The optically functional layer has a function of transmitting the first light and reflecting the second light
Data Source
AI summary
A display device having high light-extraction efficiency is provided. A low-power display device is provided. In a red or green pixel included in the display device, a light-emitting element, an optically functional layer, and a wavelength-conversion layer are stacked in this order. The light-emitting element emits blue light, the optically functional layer transmits the blue light and reflects red and green light, and the wavelength-conversion layer converts the blue light into red or green light. The blue light emitted by the light-emitting element passes through the optically functional layer and enters the wavelength-conversion layer, and red or green light is emitted to the outside. The red or green light emitted from the wavelength-conversion layer to the optically functional layer side is reflected by the optically functional layer and emitted to the outside, which improves light-extraction efficiency.