Single Crystal Phosphor Light-Emitting Device
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Solution Overview
Problem
The luminous efficiency of light-emitting devices using particulate phosphors deteriorates over time due to binding agent degradation and increased surface area vulnerability to environmental factors, leading to uneven emission and reduced excitation efficiency.
Innovation Solution
A light-emitting device employing a single monocrystal phosphor, such as Yttrium Aluminum Garnet (YAG) or Terbium Scandium Lutetium Aluminum Garnet (TSLAG), with specific compositional ranges to enhance stability and excitation efficiency, eliminating the need for a binding agent and reducing surface area exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If particulate phosphors with small grain size are used to suppress unevenness in emission color, then emission uniformity is improved, but the surface area to volume ratio increases making the phosphor more vulnerable to environmental factors and reducing excitation efficiency
Solution Approach 1:
The patent changes the fundamental parameter of phosphor morphology from particulate to single crystal form. This transformation maintains the benefits of fine grain size for emission uniformity while eliminating the harmful surface area effects through the inherent structural advantages of single crystal growth, where the entire phosphor volume constitutes a single continuous crystal lattice with minimal surface defects.
Solution Approach 2:
The patent employs a composite structure combining the semiconductor light-emitting element with a single crystal phosphor material. This composite design allows the phosphor to be directly coupled to the light-emitting element surface, creating an integrated structure where the single crystal phosphor layer converts the emitted blue light to yellow light, achieving both uniform emission and protection from environmental degradation.
2Ease of manufacture
If particulate phosphors are used, then the device structure is simpler to manufacture, but the binding agent deteriorates over time causing luminous efficiency to decrease
Solution Approach 1:
The patent extracts and eliminates the binding agent component from the phosphor application system. By using a single crystal phosphor that can be directly grown or coupled to the light-emitting element, the invention removes the epoxy resin binding agent that would otherwise deteriorate over time, thereby solving the reliability issue while maintaining manufacturing feasibility through direct crystal growth methods.
Solution Approach 2:
The single crystal phosphor is prepared in advance through controlled crystal growth processes before being integrated with the light-emitting element. This preliminary action of growing a defect-free single crystal structure ensures long-term stability and eliminates the need for binding agents, as the crystal is directly formed in its final functional configuration.
3Reliability
If single crystal phosphor is used to eliminate binding agent and reduce surface area, then luminous efficiency stability is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent merges the phosphor manufacturing process with the light-emitting element fabrication process. By directly growing the single crystal phosphor on the light-emitting element surface or integrating them in a unified manufacturing sequence, the invention reduces overall process complexity despite the advanced nature of single crystal growth, achieving both reliability improvement and manufacturing efficiency.
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 suppresses luminous efficiency deterioration, improves uniformity and crystalline quality, and enhances the device's performance under high-power excitation, maintaining efficiency over long-term use.
Implementation Method 1
a phosphor to be excited by receiving the light from the light-emitting element so as to emit a yellow light
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3C
AI summary
[Problem] To provide a light-emitting device which does not undergo the deterioration in luminous efficiency associated with the long-term use. [Solution] A light-emitting device (1) comprises a light-emitting element (10) which can emit blue light and a phosphor (2) which is composed of a single kind of single crystal and can emit yellow light upon the irradiation with the light emitted from the light-emitting element (10) which serves as excitation light. Thus, it becomes possible to prevent the deterioration in luminous efficiency associated with the deterioration in a binder or the like compared with a light-emitting device which utilizes multiple kinds of granular phosphors, because any binder for binding phosphors to each other is not required in the light-emitting device (1).