Light-Emitting Device Using TADF and Quantum Dot Layers
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Solution Overview
Problem
Quantum dot light emitting devices have low emitting efficiency due to limited internal quantum efficiency of quantum dot materials when used for generating white light through color mixing.
Innovation Solution
Incorporating a thermally activated delayed fluorescence (TADF) material layer that emits blue light and quantum dot material layers emitting yellow and green light, with energy transfer mechanisms to enhance light emission efficiency, forming a multi-layer structure within the light emitting device to combine light into white light with improved purity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If quantum dot light emitting layers are stacked to generate white light through color mixing, then white light emission is achieved, but the emitting efficiency is low
Solution Approach 1:
The patent combines quantum dot materials with thermally activated delayed fluorescence (TADF) materials to form a composite light emitting layer. This composite structure allows the TADF material to convert triplet excitons to singlet excitons, which then transfer energy to the quantum dots, significantly improving the overall emitting efficiency while maintaining white light emission through color mixing of multiple quantum dot layers
2Illumination intensity
If quantum dot materials are used for white light generation, then color mixing is achieved, but the internal quantum efficiency is limited
Solution Approach 1:
The TADF material serves as an intermediary between the injected carriers and the quantum dot materials. It receives energy from carrier recombination, converts triplet excitons to singlet excitons through reverse intersystem crossing, and then transfers this energy to the quantum dots. This intermediary mechanism overcomes the limited internal quantum efficiency of direct quantum dot excitation while preserving the color mixing capability
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 use of TADF material layers significantly enhances the light emitting efficiency by converting triplet excitons to singlet excitons, improving the overall efficiency of the light emitting device and achieving stable white light emission with higher purity by combining blue, yellow, and green light.
Implementation Method 1
the light emitting layer includes N stacked light emitting units, each of the light emitting units includes a thermally activated delayed fluorescence material layer and a quantum dot material layer
Implementation Method 2
the thermally activated delayed fluorescence material not only emits light by itself, but also transfers energy to the quantum dot material layer to excite the quantum dot material to emit light
Implementation Method 3
Quantum Dot is a quasi-zero-dimensional nano-material with significant quantum size effect. The luminescence spectrum of quantum dots can be controlled by changing the size of quantum dots
Implementation Method 4
white light is obtained by color mixing, such as a quantum dot light emitting layer stack that respectively emits red light, green light, and blue light to generate white light
Data Source
AI summary
The present application relates to a light-emitting device, comprising an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode, which are stacked in sequence, wherein the light-emitting layer comprises N stacked light-emitting units; each light-emitting unit comprises a thermal activation delayed fluorescent material layer and a quantum dot material layer; the light emitted from the thermal activation delayed fluorescent material layer and the light emitted from the quantum dot material layer are synthesized into white light.