Perovskite Red Phosphor for LED Color Rendering
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Solution Overview
Problem
Existing red phosphors used in white LEDs, such as those with nitride compositions, require specialized synthesis conditions, leading to high manufacturing costs and are prone to chromaticity deviations due to light absorption issues, making it difficult to achieve high color rendering properties.
Innovation Solution
A red phosphor with a perovskite crystal structure (ABX3) where the emission element is located at the B site, utilizing a combination of anions like oxygen and fluorine to create a non-uniform electron density, resulting in a large Stokes shift and efficient low-energy excitation, reducing absorption of visible light from other phosphors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nitride phosphors are used to achieve red emission, then color rendering properties are improved, but manufacturing cost increases due to specialized synthesis conditions
Solution Approach 1:
The patent changes the crystal structure parameter from nitride to perovskite oxide, which fundamentally alters the synthesis conditions. The perovskite structure allows synthesis in conventional atmospheric conditions rather than requiring specialized deoxidized or high-pressure environments, thereby reducing manufacturing cost while maintaining red emission properties through the ABX3 structure with emission element at the B site
Solution Approach 2:
The patent employs a composite perovskite structure combining A-site cations, B-site emission elements, and X-site anions (oxygen and fluorine). This composite approach creates a material that achieves both the desired red emission for color rendering and compatibility with standard manufacturing processes, resolving the contradiction between performance and ease of manufacture
2Reliability
If red phosphor with excitation edge at 500-550 nm is used, then red emission is achieved, but chromaticity deviates due to light absorption from other phosphors
Solution Approach 1:
The patent shifts the excitation edge parameter to the ultraviolet region through the perovskite crystal structure design. This parameter change eliminates the overlap with visible light emission from other phosphors (blue, green, yellow), preventing unwanted absorption and chromaticity deviation while maintaining effective red emission
Solution Approach 2:
The perovskite crystal structure acts as an intermediary that decouples the excitation and emission wavelengths. By positioning the excitation edge in the ultraviolet region, the structure mediates between the pump light source and the red emission, preventing direct interaction between the red phosphor and visible light from other phosphors, thereby stabilizing chromaticity
3Use of energy by moving object
If red phosphor absorbs visible light from other phosphors, then energy transfer occurs, but luminous efficacy decreases
Solution Approach 1:
The patent extracts the problematic visible light absorption characteristic from the red phosphor system by positioning the excitation edge in the ultraviolet region. This extraction eliminates the harmful energy transfer pathway from visible light-emitting phosphors, preventing energy loss and improving overall luminous efficacy while maintaining the desired red emission
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 achieves stable temperature characteristics and improved color accuracy by minimizing light absorption, allowing for better color rendering and luminous efficacy in white LEDs.
Implementation Method 1
utilizing a combination of anions like oxygen and fluorine to create a non-uniform electron density, resulting in a large Stokes shift and efficient low-energy excitation
Implementation Method 2
an emission element is located at a B site serving as a body center of the perovskite crystal structure
Data Source
AI summary
In a phosphor according to an aspect, an emission site has a perovskite crystal structure expressed by ABX3, in which A and B are each a cation and X is an anion, and an emission element is located at a B site serving as a body center of the perovskite crystal structure.