Stratified Quantum Dot Phosphor for Micro-LEDs
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Solution Overview
Problem
Current light emitting diode (LED) devices with quantum dot (QD) color conversion structures face challenges such as high operating temperatures, photon flux, and tight packing, leading to emission quenching and degradation, particularly in miniaturized micro-LEDs, where QDs are often embedded in polymeric matrices that can cause interactions reducing conversion efficiency.
Innovation Solution
A micro-LED structure with a stratified QD color conversion approach where QDs are applied directly as discrete particles between encapsulation layers, eliminating the need for a polymeric matrix, allowing for minimal QD usage and less expensive deposition techniques, with multiple layers of QDs emitting different colors for efficient light conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If QDs are embedded in a polymeric matrix, then QD distribution and protection are improved, but QD-QD interactions increase leading to emission quenching and reduced conversion efficiency
Solution Approach 1:
The patent extracts QDs from the polymeric matrix environment and places them directly on the LED chip surface. This removal of the matrix eliminates the harmful QD-QD interactions and emission quenching while maintaining QD protection through a different approach (direct deposition and encapsulation).
Solution Approach 2:
The patent introduces an intermediary layer (encapsulation layer) that protects the QDs without requiring a polymeric matrix. This intermediary provides protection while allowing optical transmission and preventing harmful interactions, replacing the traditional matrix-mediated protection approach.
2Reliability
If QD film thickness is increased to maintain complete light conversion, then conversion efficiency is improved, but device thickness increases which is unacceptable for miniaturized micro-LEDs
Solution Approach 1:
The patent changes the key parameter of QD concentration/loading from low (in matrix) to high (direct deposition). This parameter change allows achieving complete light conversion with a much thinner film, enabling miniaturization while maintaining conversion efficiency.
Solution Approach 2:
The patent creates a composite structure with multiple layers (encapsulation layer, QD layer, another encapsulation layer) where each layer has a specific function. This composite approach allows thin film thickness while maintaining complete light conversion through optimized layer composition and arrangement.
3Stability of the object's composition
If QD concentration in matrix is low, then QD dispersion is improved, but film thickness must be increased to achieve complete light conversion
Solution Approach 1:
The patent removes QDs from the matrix environment entirely, placing them directly on the LED chip. This extraction eliminates the need for low concentration dispersion while achieving high QD density for complete light conversion in a thin film.
Solution Approach 2:
The patent employs liquid precursor deposition (a fluid-based approach) to achieve uniform QD distribution directly on the chip surface. This hydraulic/pneumatic deposition method ensures even QD distribution without requiring low concentration in a matrix, enabling thin film formation with complete light conversion.
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 enables even QD distribution, minimizes interactions, and enhances conversion efficiency by using discrete QD layers encapsulated in barrier layers, reducing emission quenching and degradation, while allowing for thinner films suitable for micro-LEDs and cost-effective processing.
Implementation Method 1
The first layer of QDs emits a first color of light in the visible spectrum, different than the first wavelength of light, in response to converting the first wavelength of light
Data Source
AI summary
A method is presented for fabricating a light emitting diode (LED) device with a stratified quantum dot (QD) structure. The method provides an LED and a stratified QD structure is formed as follows. A first liquid precursor is deposited overlying the LED emission surface to form a transparent first barrier layer. A second liquid precursor is deposited overlying the first barrier layer to form a first layer of discrete QDs. A third liquid precursor is deposited overlying the first layer of QDs to form a transparent second barrier layer. Subsequent to each barrier layer liquid precursor deposition, an annealing is performed to cure the deposited precursor. The first and second barrier layers act to encapsulate the first layer of QDs. The LED emits a first wavelength of light, and the first layer of QDs converts the first wavelength of light to a first color of light in the visible spectrum.