InP Core-Shell Nanoparticles for Cd-Free Wavelength Conversion
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Solution Overview
Problem
Displays using QD patternings as wavelength conversion layers face challenges with low absorption coefficients due to structural limitations, leading to mixed colors when blue light is not sufficiently absorbed, and existing shell materials with higher absorption coefficients contain toxic Cd.
Innovation Solution
A wavelength conversion layer with InP-based semiconductor nanoparticles featuring a core-shell structure, where the shell is composed of ZnXTe (X = Se or S) to enhance blue light absorption while maintaining high stability and avoiding Cd toxicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional shell materials (e.g., CdZnSeS) are used to increase absorption coefficient, then blue light absorption is improved, but toxicity increases due to Cd content
Solution Approach 1:
The patent changes the chemical composition parameters of the shell material from conventional Cd-based materials to InP-based materials with specific composition ratios. The core semiconductor nanoparticles have a composition of In1-xP1-y where x and y are controlled within specific ranges (0 < x ≤ 0.5, 0 < y ≤ 0.5), which fundamentally alters the material properties to eliminate toxicity while maintaining or improving optical absorption characteristics.
Solution Approach 2:
The patent employs composite material structures with core-shell architecture. The core is made of InP-based semiconductor nanoparticles, and the shell is made of specific materials that provide both protective functions and enhanced optical absorption. This composite structure combines the advantages of different materials to achieve high absorption coefficient without toxicity.
2Length of stationary object
If QD patternings with thickness of 5 μm to 10 μm are used, then structural limitations are satisfied, but absorption coefficient decreases due to limited number of semiconductor nanoparticles
Solution Approach 1:
The patent optimizes the thickness parameter of the QD patterning layer to be within 5 μm to 10 μm, which satisfies structural limitations of display devices. Within this constrained thickness range, the patent achieves high absorption by optimizing the composition and arrangement of semiconductor nanoparticles, rather than increasing thickness.
Solution Approach 2:
The patent creates a patterned structure that replicates the desired optical function through spatial arrangement. The QD patterning layer uses specifically designed patterns of semiconductor nanoparticles that maximize light absorption within the limited thickness, effectively copying the function of thicker layers through optimized geometric configuration.
3Reliability
If blue light is not sufficiently absorbed by QD patternings, then mixed color occurs, but increasing absorption requires higher concentration of semiconductor nanoparticles which increases complexity
Solution Approach 1:
The patent optimizes the concentration and size distribution parameters of semiconductor nanoparticles to achieve sufficient blue light absorption. By controlling the particle size within specific ranges and optimizing the composition ratios (x and y values), the patent achieves high absorption efficiency without requiring excessive nanoparticle concentration, thus maintaining color purity while avoiding excessive 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 solution provides a wavelength conversion layer with increased absorption coefficient for blue light, ensuring high stability and eliminating Cd toxicity, thereby preventing mixed colors and expanding the color gamut in displays.
Implementation Method 1
Excitons formed within the semiconductor nanoparticles by some means, such as photoexcitation or charge injection, recombine to release photons of energy corresponding to the band gap; accordingly, emission of light of a desired wavelength can be obtained
Implementation Method 2
shell materials capable of absorbing blue light contain Cd, for instance as in CdZnSeS
Data Source
AI summary
The purpose of the present invention to provide a wavelength conversion layer containing semiconductor nanoparticles substantially containing no Cd, and which have an increased absorption coefficient to blue light while maintaining high stability. A wavelength conversion layer containing semiconductor nanoparticles, wherein the wavelength conversion layer can convert light having a wavelength of 450 nm to light having a peak wavelength of 500 nm to 550 nm, or light having a peak wavelength of 600 nm to 660 nm; each of the semiconductor nanoparticles contained in the wavelength conversion layer has a core and a shell having one or more layers; the core contains In and P; and at least one layer of the shell is ZnXTe (wherein X represents Se or S, or both Se and S).