Quantum Dot Electroluminescence Element White Light Emission
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Solution Overview
Problem
Existing white light-emitting organic electroluminescence elements have poor color rendering properties and short service life due to the need for multiple light-emitting layers and the use of phosphorescence-emitting materials, which complicates production and reduces durability.
Innovation Solution
An electroluminescence element with a light-emitting layer containing quantum dot materials, where the particle size distribution is defined by d90−d10 ≥ 3 nm, and optionally includes a core-shell structure and surface modification, to achieve improved color rendering and longevity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple light-emitting layers are laminated to produce white light, then white light emission is achieved, but device complexity and production difficulty increase
Solution Approach 1:
The patent segments the white light emission function into multiple quantum dot materials with different particle sizes within a single light-emitting layer. By controlling the particle size distribution (d90-d10 ≥ 3 nm), different quantum dots emit different wavelengths that combine to form white light, eliminating the need for multiple laminated layers while maintaining the white light emission function.
Solution Approach 2:
The patent merges multiple quantum dot materials with different emission characteristics into a single light-emitting layer. This combination approach allows simultaneous emission of multiple wavelengths from one layer, achieving white light without the complexity of laminating separate light-emitting layers for different colors.
2Use of energy by moving object
If phosphorescence-emitting materials are used to achieve white light emission, then luminous efficiency improves, but service life and durability deteriorate
Solution Approach 1:
The patent changes the material parameter from phosphorescence-emitting organic materials to quantum dot materials with specific particle size distributions. This parameter change maintains high luminous efficiency through quantum confinement effects while dramatically improving service life, as quantum dots are inorganic materials with superior stability and resistance to degradation compared to organic phosphorescence materials.
3Measurement precision
If quantum dot material with narrow particle size distribution is used, then emission spectrum is sharp, but color rendering properties deteriorate
Solution Approach 1:
The patent applies local quality by creating a controlled distribution of particle sizes within specific ranges. Rather than using uniform particle sizes (which would give sharp but poor color rendering) or completely random sizes, the patent optimizes the local particle size characteristics to achieve both adequate spectral definition and broad wavelength coverage for excellent color rendering (Ra≥90, R9≥90).
Solution Approach 2:
The patent changes the particle size distribution parameters to satisfy d90-d10 ≥ 3 nm, which broadens the emission spectrum compared to narrow distributions while maintaining sufficient spectral resolution. This parameter optimization enables the quantum dot material to emit across a wide wavelength range with multiple peaks, achieving excellent color rendering properties.
4Ease of manufacture
If single light-emitting layer with quantum dots is used, then production process is simplified, but color rendering properties may deteriorate without proper particle size control
Solution Approach 1:
The patent establishes specific particle size distribution parameters (d90-d10 ≥ 3 nm) as critical control points in the manufacturing process. By focusing quality control on this key parameter during quantum dot synthesis and film formation, the patent ensures excellent color rendering properties are achieved while maintaining the production simplicity of a single-layer structure.
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 provides an electroluminescence element with enhanced color rendering properties and extended service life by using quantum dot materials with specific particle size distributions and surface modifications, simplifying production and improving luminous efficacy.
Implementation Method 1
An organic EL element is a thin film-type all-solid element including a film, a pair of positive and negative electrodes formed on the film, and a functional layer (single layer part or multi-layered part) that is sandwiched between the electrodes, contains an organic light-emitting substance, and has a thickness of only about 0.1 μm. When a relatively low voltage of about 2 to 20 V is applied to such an organic EL device, electrons and holes are injected into the organic compound layer from the negative electrode and the positive electrode, respectively. It is known that these electrons and holes recombine in the light-emitting layer, and energy is emitted as light when the energy level returns from the conduction band to the valence band so that luminescence occurs.
Implementation Method 2
A quantum dot material has a sharp emission spectrum, is an inorganic material and therefore excellent in durability, and is soluble in various solvents and therefore applicable to a coating process.
Data Source
AI summary
Disclosed herein is an electroluminescence element that is excellent in color rendering properties and has a long service life as a white light-emitting element, that is, high durability. The electroluminescence element (100) includes: a substrate (1); a first electrode (2); a functional layer (20) including at least one light-emitting layer (5); and a second electrode (8), wherein the at least one light-emitting layer (5) contains a quantum dot material (11), and wherein when a particle size at a cumulative frequency of 10% and a particle size at a cumulative frequency of 90% in a volume-based cumulative particle size distribution of the quantum dot material (11) are defined as d10 (nm) and d90 (nm), respectively, the quantum dot material (11) satisfies d90−d10≧3 nm.