Lu-Ce-Y Phosphor Reduces Light Loss in White LEDs
Solution Overview
Problem
Current white LEDs with yellow phosphors like YAG suffer from light loss in the 455-500 nm wavelength region and have limited color rendering properties due to the low emission quantum efficiency of red phosphors containing Eu as a luminescent center, especially under high-energy excitation.
Innovation Solution
A phosphor with a crystal phase of (Lu1-p-q, Ce p, M q) x β y γ z O, where M includes Y and other elements, exhibits a broad emission spectrum with a peak between 540-600 nm and significant intensity at 500 nm, reducing light loss and improving color rendering by extending the choice of excitation light sources and enhancing luminance saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional yellow phosphor (YAG) is used with a blue LED chip, then the white LED can be manufactured with simple structure, but light loss occurs in the wavelength region of 455-500 nm and color rendering properties are limited
Solution Approach 1:
The patent modifies the phosphor's chemical composition parameters by incorporating Lu, Ce, and Y in specific ratios (0 < p ≤ 0.1, 0 < q ≤ 0.5, p+q ≤ 1) into the host lattice (Lu1-p-q, Ce p, M q) x Siy Nz O. This compositional parameter change extends the emission spectrum to cover the 455-500 nm region while maintaining manufacturing feasibility through established solid-state reaction methods
Solution Approach 2:
The patent creates a composite phosphor material combining multiple elements (Lu, Ce, Y, Si, N, O) in a specific structural framework. The composite nature of (Lu1-p-q, Ce p, M q) x Siy Nz O allows simultaneous achievement of broad emission spectrum (reducing light loss) and compatibility with conventional LED manufacturing processes
2Illumination intensity
If a red phosphor containing Eu as luminescent center is used, then the emission color can be adjusted, but the emission quantum efficiency is low under high-energy excitation due to longer emission lifetime causing luminance saturation
Solution Approach 1:
The patent uses Ce3+ ions as a substitute for Eu2+ ions in the phosphor structure, creating a Ce-doped phosphor that copies the functional role of Eu-based red phosphors. Ce3+ provides similar color adjustment capability through variable doping concentrations while achieving shorter emission lifetime and higher quantum efficiency under high-energy excitation, thus resolving the luminance saturation problem
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 phosphor effectively reduces light loss in the 455-500 nm range and enhances color rendering properties, making it suitable for high-power white-light sources with improved luminance and quantum efficiency.
Implementation Method 1
light from a blue LED chip is partly subjected to color conversion with a phosphor, and blue light from the blue LED chip and light from the phosphor are mixed to produce white light
Data Source
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AI summary
A phosphor comprises a crystal phase with a chemical composition (Lu1-p-q, Cep, Mq)xβyγzO. M denotes one or more elements selected from the group consisting of Y, La, Sc, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. β contains Si, which constitutes 90% or more by mole of β. γ contains N, which constitutes 90% or more by mole of γ. The variables x, y, z, p, and q satisfy 5.5 ≤ x ≤ 6.5, 10.5 ≤ y ≤ 11.5, 19.5 ≤ z ≤ 20.5, 0 < p < 0.03, and 0 ≤ q ≤ 0.5.