Core-Multishell Upconversion Nanophosphor for Bright RGB Emission
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Solution Overview
Problem
Existing upconversion nanophosphors struggle to emit a variety of colors efficiently and maintain high brightness, particularly when implementing blue, green, and red light, limiting their application in 3-dimensional transparent displays.
Innovation Solution
A hexagonal core/multishell upconversion nanophosphor structure is developed, comprising a Tm3+-doped fluoride core, Yb3+, Er3+-co-doped green-emitting shell, Nd3+, Yb3+-co-doped absorption shell, Tm3+-doped blue-emitting shell, and outermost crystalline shell, enabling emission of blue, green, and red light by varying laser wavelengths without significant brightness reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If upconversion nanophosphors of various compositions are mixed to achieve multiple colors, then color variety is improved, but emission purity and brightness are degraded
Solution Approach 1:
The nanophosphor is divided into multiple shells, each containing different lanthanide elements (Tm3+, Er3+, Ho3+) that emit specific colors. The core contains Tm3+ for blue emission, first shell contains Er3+ for green emission, second shell contains Ho3+ for red emission. This segmentation allows each shell to independently emit its characteristic color with high brightness without the need to mix different nanophosphor compositions, thus resolving the contradiction between color variety and emission brightness.
2Adaptability or versatility
If core/quad-shell upconversion nanophosphor is used to emit multiple colors, then color tunability is improved, but upconversion luminescence intensity is degraded
Solution Approach 1:
Multiple emitting shells are merged into a single core/multishell nanophosphor structure, where the core and each shell work together to produce upconversion luminescence. The core contains Tm3+ ions that can be excited by NIR light to emit blue light, while the shells contain Er3+ and Ho3+ ions that emit green and red light respectively. This merging allows simultaneous multi-color emission with high luminescence intensity, avoiding the energy loss associated with pulse laser control methods.
3Adaptability or versatility
If 808 nm NIR excitation is used for blue light emission, then blue emission is achieved, but emission efficiency is degraded
Solution Approach 1:
The excitation wavelength parameter is changed from conventional 808 nm to 980 nm NIR light. This parameter change enables more efficient excitation of Tm3+ ions in the core, resulting in enhanced blue upconversion luminescence efficiency. The 980 nm excitation wavelength matches the absorption characteristics of Tm3+ ions more effectively, reducing energy loss and improving overall emission efficiency while maintaining blue light emission capability.
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 nanophosphor achieves efficient emission of multiple colors with high brightness, suitable for 3-dimensional transparent displays and anti-counterfeiting technologies.
Implementation Method 1
some lanthanide elements cause an anti-Stokes shift by which the nanophosphor is excited by infrared (IR) light and emits light having a shorter wavelength than the excitation light, i.e., higher-energy visible light. This type of luminescence is called upconversion luminescence because the energy of the emitted light is increased compared to the energy of the light that excites the nanophosphor
Implementation Method 2
some lanthanide elements cause an anti-Stokes shift by which the nanophosphor is excited by infrared (IR) light and emits light having a shorter wavelength than the excitation light
Implementation Method 3
Most nanophosphors doped with lanthanide elements absorb high-energy light such as ultraviolet (UV) or visible light from the outside and emit visible light with a longer wavelength than the absorbed light. The difference between the absorption wavelength and the emission wavelength is called a Stokes shift
Data Source
AI summary
Provided are a core-multishell upconversion nanophosphor capable of being excited by 800±20 nm, 980±20 nm, and 1530±20 nm near-infrared (NIR) light to emit various colors including green, red, blue, and combinations thereof, and a transparent polymer composite including the upconversion nanophosphor. A crystalline shell may be formed between the red, green, and blue emission layers to enable emission of pure red, green, or blue light, and be further formed on an outermost surface to provide a color-tunable and high-brightness upconversion nanophosphor.