Phosphor Light Emitter Bandgap Tuning Against Output Saturation
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Solution Overview
Problem
Light emitting devices using phosphors with long luminescence lifetimes experience output saturation when excited with high energy density laser beams, limiting the intensity of fluorescence emitted.
Innovation Solution
A light emitting device with a primary light source emitting energy exceeding 0.5 W/mm² and a first phosphor that absorbs this light, converting it into a wavelength-converted light with a wavelength longer than the primary light, where the host compound has a bandgap energy greater than the sum of the primary light's and wavelength-converted light's energy values, preventing excited state absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a phosphor having a long luminescence lifetime is used to enhance wavelength selection freedom and afterglow property, then the degree of freedom in wavelength selection and afterglow property are improved, but fluorescence output saturation occurs when excited with high energy density laser beams
Solution Approach 1:
The invention changes the energy parameter relationship by selecting a phosphor material whose bandgap energy is greater than the sum of the primary light energy and wavelength-converted light energy. This parameter selection prevents excited state absorption and eliminates fluorescence output saturation, allowing long-luminescence lifetime phosphors to operate at high energy densities without performance degradation.
2Illumination intensity
If the energy density of the laser beam is increased to enhance fluorescence intensity, then the intensity of light emitted by the phosphor increases, but fluorescence output saturation occurs when the energy density exceeds a predetermined value
Solution Approach 1:
The invention identifies and controls the critical energy parameter relationship: bandgap energy must exceed the sum of primary light energy and converted light energy. By maintaining this parameter relationship, the system can continuously increase primary light energy density to enhance fluorescence intensity without encountering output saturation, effectively removing the predetermined energy density limit.
3Productivity
If a phosphor with short luminescence lifetime is used to prevent output saturation, then fluorescence output saturation is prevented, but the degree of freedom in wavelength selection and afterglow property are limited
Solution Approach 1:
The invention changes the fundamental parameter relationship that causes saturation. By selecting phosphor materials where the bandgap energy is greater than the sum of primary and converted light energies, the system eliminates the saturation mechanism entirely. This allows long-luminescence lifetime phosphors to be used without sacrificing output intensity, thereby restoring full adaptability in wavelength selection and afterglow properties.
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
Prevents fluorescence output saturation even with phosphors having long luminescence lifetimes, allowing for high-intensity near-infrared light emission suitable for medical applications like fluorescence imaging and photodynamic therapy.
Implementation Method 1
a first phosphor that absorbs the primary light to convert the primary light into a first wavelength-converted light having a wavelength longer than that of the primary light
Implementation Method 2
a bandgap energy of a crystal of the simple oxide is larger than a sum of the E1 electron volts and the E2 electron volts
Data Source
AI summary
A light emitting device includes a light source that emits a primary light having a light energy density exceeding 0.5W/mm2, and a first phosphor that absorbs the primary light to convert the primary light into a first wavelength-converted light having a wavelength longer than that of the primary light. The first phosphor includes a compound serving as a host, the compound being a simple oxide including one kind of metal element or a composite oxide including a plurality of different kinds of the simple oxide as an end member. When an energy conversion value at a peak wavelength of the primary light is E1 electron volts and an energy conversion value at a fluorescence peak wavelength of the first wavelength-converted light is E2 electron volts, a bandgap energy of a crystal of the simple oxide is larger than a sum of the E1 electron volts and the E2 electron volts.