Core Shell Quantum Dots High Luminous Efficacy
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Solution Overview
Problem
Current core shell quantum dots exhibit insufficient luminous efficacy due to surface defects and exciton trapping, which affects their emission characteristics.
Innovation Solution
A core shell particle configuration is developed where the molar ratio of Group II elements to Group III elements in the core shell particle is set to 2.7 or greater, with a specific composition and structure involving a Group III-V semiconductor core, a Group II-VI or Group III-V semiconductor first shell, and a Group II-VI semiconductor second shell, optimized for high luminous efficacy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional core shell quantum dots are used, then the basic optical characteristics are achieved, but the luminous efficacy is insufficient due to surface defects and exciton trapping
Solution Approach 1:
The quantum dot is divided into distinct functional layers: a Group III-V core, a Group II-VI first shell, and a Group III-V second shell. This segmentation allows each layer to perform specific functions - the core provides the basic optical properties, the first shell passivates surface defects, and the second shell further reduces exciton trapping, collectively improving luminous efficacy
Solution Approach 2:
The patent employs composite material structure combining different semiconductor materials with complementary properties. The Group III-V core material (e.g., InP) provides strong optical absorption, while the Group II-VI shell material (e.g., ZnS) provides excellent surface passivation. This composite approach synergistically improves both optical performance and luminous efficacy by eliminating the harmful effects of surface defects
2Illumination intensity
If the particle diameter is decreased to several nanometers, then quantum size effects are achieved with larger band gap and short wavelength emission, but surface defects and exciton trapping increase
Solution Approach 1:
Different regions of the quantum dot are assigned different material compositions optimized for their specific functions. The core region maintains small diameter for quantum size effects and short wavelength emission, while the shell regions provide localized surface passivation. This local quality differentiation allows the particle to simultaneously achieve desired optical characteristics and minimize surface defects
Solution Approach 2:
The Group II-VI first shell acts as an intermediary layer between the Group III-V core and the external environment. This intermediate layer passivates the core surface, reducing exciton trapping while maintaining the quantum size effects and optical properties of the small-diameter core
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 configuration significantly enhances luminous efficacy by reducing exciton trapping and surface defects, resulting in improved emission characteristics and a narrow luminous half-width.
Implementation Method 1
The particle diameter of these semiconductor fine particles is several nanometers to several tens of nanometers. Further, a band gap typically becomes larger as the particle diameter of particles having such a nanoscale decreases due to so-called quantum size effects, and the particles exhibit light emission in a short wavelength range such as an ultraviolet region or a near ultraviolet region.
Implementation Method 2
the molar ratio of the Group II element contained in the entirety of the core shell particle to the Group III element contained in the core, which is acquired using X-ray photoelectron spectroscopy
Data Source
AI summary
An object of the present invention is to provide a core shell particle exhibiting high luminous efficacy, a method of producing the core shell particle, and a film containing the core shell particle. The core shell particle of the present invention includes a core which contains a Group III element and a Group V element; a first shell which covers at least a part of a surface of the core; and a second shell which contains a Group II element and covers at least a part of the first shell, in which the molar ratio of the Group II element contained in the entirety of the core shell particle to the Group III element contained in the core, which is acquired using X-ray photoelectron spectroscopy, is 2.7 or greater.