Quantum Dot Display Pixel Structure for Color Space Reproduction
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Solution Overview
Problem
LED displays with conversion layers face challenges in achieving high contrast ratios and reproducing specific color spaces due to the limitations of deep blue or UV excitation sources, which result in increased material requirements, energy loss, and sensitivity to temperature variations, while also complicating manufacturing processes.
Innovation Solution
Implementing a pixel structure with three sub-pixels using the same deep blue LEDs, each covered with a wavelength converting layer designed to emit red, green, and blue light, respectively, to create a new blue color point that aligns with standard color spaces like Rec709 and Rec2020, allowing for efficient color reproduction without the need for multiple blue LEDs and minimizing material concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If deep blue or UV excitation sources are used to achieve high absorption cross-section, then the absorption efficiency of color conversion material is improved, but the material concentration requirement increases and reabsorption loss increases
Solution Approach 1:
The patent introduces a spectral dimension by using a blue light source with a specific spectral distribution that has reduced intensity in the 470-490nm range. This spectral shaping allows the system to achieve high absorption efficiency at the exciton peak while reducing the overlap with emission wavelengths, thereby minimizing reabsorption loss and reducing the required material concentration.
Solution Approach 2:
The patent changes the spectral parameters of the excitation source by selecting a blue LED with a peak wavelength and spectral distribution that optimizes the absorption cross-section of the quantum dots while minimizing reabsorption. This parameter optimization allows achieving high conversion efficiency with lower material concentration.
2Use of energy by moving object
If deep blue or UV excitation sources are used to achieve high absorption cross-section, then the absorption efficiency of color conversion material is improved, but energy loss increases due to Stokes shift
Solution Approach 1:
The patent optimizes the excitation wavelength parameter to be close to the emission wavelength (minimizing the Stokes shift) while still achieving high absorption cross-section. By selecting a blue LED with peak wavelength strategically positioned relative to the quantum dot emission spectrum, the system reduces the energy difference between absorbed and emitted photons, thereby minimizing energy loss.
3Use of energy by moving object
If deep blue or UV excitation sources are used, then the absorption cross-section is improved, but temperature sensitivity of conversion layers increases
Solution Approach 1:
The patent selects excitation and emission wavelengths that minimize the thermal broadening effects. By operating at wavelengths where the absorption and emission spectra have optimal overlap and where the quantum dot photophysics are less sensitive to temperature variations, the system reduces temperature sensitivity while maintaining high absorption cross-section.
4Illumination intensity
If multiple blue LEDs with different wavelengths are used to achieve target blue color point, then color space reproduction is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent merges the functions of multiple light sources with different wavelengths into a single blue LED source. By carefully selecting a blue LED with an optimized spectral distribution and combining it with quantum dot wavelength conversion, the system achieves the target blue color point and comprehensive color space reproduction that would otherwise require multiple different wavelength LEDs, thereby simplifying the device structure and manufacturing.
Solution Approach 2:
The patent makes a single blue LED source perform multiple functions: it provides the primary blue light for the blue sub-pixel, serves as the excitation source for the red and green quantum dot converters, and through spectral optimization, enables accurate color space reproduction. This multi-functionality eliminates the need for multiple specialized light sources.
5Illumination intensity
If multiple blue LEDs with different wavelengths are used to achieve target blue color point, then color space reproduction is improved, but manufacturing process complexity increases
Solution Approach 1:
The patent combines the requirements of color space reproduction and manufacturing simplicity by using a single blue LED wavelength that can be mass-produced with consistent characteristics. This approach allows standardization of the light source component, enabling efficient manufacturing processes such as inkjet printing of quantum dots directly onto the LED, whereas multiple wavelength LEDs would require complex sorting and selection processes.
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 energy conversion efficiency, reduces material requirements, and simplifies manufacturing by using identical LEDs, while maintaining high contrast ratios and achieving the desired color gamut within standard color spaces.
Implementation Method 1
each micro LED device is designed to emit a deep blue (DB) color spectrum. The different wavelength converting layers can be designed to emit red (R), green (G), and blue (B)
Implementation Method 2
The absorption cross-section of an NPL (Nanoplatelet) or QDOT depends on the excitation wavelength. For a particular conversion material there may be a peak in the absorbance. FIG. 7 shows the spectrum of a LumidotTM CdSe/ZnS 610 nm red emitting quantum dot particles. The line 710 represents the absorption spectrum. As can be seen in the Figure, there is a local absorption peak 730 (due to the first exciton level) close to the emission peak, but the absorbance is much stronger for wavelengths below 500 nm
Data Source
AI summary
A display device including an array of pixels, each pixel including at least three sub-pixels having a LED device emitting light with a blue color point. The first sub-pixel is designed to emit red light having a first color point, the second sub-pixel is designed to emit green light having a second color point, where the LED device of the third sub-pixel is covered with a third wavelength converting layer designed to emit light having a fourth color point. The fourth color point being such that the combination of light emitted by the LED device not converted by the wavelength converting layer and the light converted by the wavelength converting layer results in light having a third color point, where the first, the second and the third color points define a second color space in which a set color space is included.