OLED Pixel Structure Using Inorganic Quantum Dots
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Solution Overview
Problem
Traditional OLEDs face issues with stability, lifetime, luminous efficiency, and energy consumption, particularly due to the degradation of organic materials and low external quantum efficiency.
Innovation Solution
The OLED pixel structure incorporates inorganic quantum dots in the blue light emitting layer, combined with a blue light filter, and optionally a white light emitting layer, to enhance stability, lifetime, and luminous efficiency, using materials like CdSe, CdS, and ZnSe quantum dots, and organic materials like Ir(piq)3 and Ir(ppy)3, with a manufacturing process involving solvent mixing and surface covering to prevent agglomeration and oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If organic electroluminescence materials are used in OLED, then the device can achieve self-illumination and high contrast, but the stability and lifetime are reduced due to material degradation
Solution Approach 1:
The patent uses inorganic quantum dots as a composite material replacement for organic electroluminescence materials in the blue sub pixel. Quantum dots provide superior heat stability and resistance to degradation compared to organic materials, directly resolving the contradiction between achieving self-illumination/high contrast and maintaining stability/lifetime. The inorganic nature of quantum dots prevents the degradation issues inherent in organic materials while preserving the light-emitting function.
2Device complexity
If organic electroluminescence materials are used, then the OLED structure can be simplified, but the external quantum efficiency is limited due to spin-statistics restrictions
Solution Approach 1:
The patent changes the material parameter from organic to inorganic quantum dots, which fundamentally alters the spin-statistics behavior. Inorganic quantum dots do not suffer from the same spin-restriction limitations as organic materials, allowing for higher external quantum efficiency. This parameter change enables the device to overcome the 25% efficiency ceiling imposed by organic material spin statistics while maintaining structural simplicity.
3Ease of manufacture
If organic materials are used for red, green and blue sub pixels, then the manufacturing process can be simplified, but the color stability changes with time due to different degradation lifetimes
Solution Approach 1:
The patent applies local quality by replacing organic materials with inorganic quantum dots specifically in the blue sub pixel, while maintaining organic materials in red and green sub pixels. This localized substitution addresses color stability issues in the blue channel (which typically degrades fastest) without completely redesigning the entire display structure, thus preserving manufacturing simplicity while improving color stability where it is most needed.
4Reliability
If inorganic quantum dots are used in the blue light emitting layer, then the heat stability and external quantum efficiency are improved, but the device complexity increases due to additional layers and materials
Solution Approach 1:
The patent extracts the quantum dot material from a complete QD-LED structure and integrates it into an existing OLED architecture. By taking out only the essential blue light emitting function and implementing it through quantum dots in a simplified manner (without the full complexity of QD-LED electron injection layers and transport layers), the patent achieves heat stability improvement while minimizing the increase in device complexity. The quantum dots are incorporated into the existing OLED layer structure rather than creating a entirely new device architecture.
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
This configuration significantly improves the stability and lifetime of OLED elements, increases luminous efficiency, and reduces energy consumption by leveraging the superior heat stability and high external quantum efficiency of inorganic quantum dots.
Implementation Method 1
With the excitation of the external energy (photoluminescence, electroluminescence, cathode ray luminescence and etc.), the electrons jumps from the ground state to the excited state. The electrons and the electron holes in the excited state may form excitons. The electrons and the electron holes generate recombinations and ultimately relax to the ground state. The supernumerary energy may irradiate and generate photons with the processes of the recombination and relaxation.
Implementation Method 2
a blue light filter is located corresponding to the blue sub pixel
Implementation Method 3
Because the size of the semiconductor nanocrystals is smaller than the Exciton Bohr Radius of the material. Strong quantum confinement effect appears. The quasicontinuum evolves to become similar to the discrete energy level of the molecules and shows new material properties. Therefore, it is so called quantum dots (QDs).
Data Source
AI summary
The present invention provides an OLED pixel structure, comprising: red, green and blue sub pixels, and the red sub pixel comprises a red light emitting layer, and the green sub pixel comprises a green light emitting layer, and the blue sub pixel comprises a blue light emitting layer, and material of the blue light emitting layer comprises inorganic quantum dots, and the blue light emitting layer emits white light, and a blue light filter is located corresponding to the blue sub pixel. By the blue sub pixel utilizing inorganic quantum dots+blue light filter, the stability and the life time of the OLED elements have been obviously promoted. The present invention further adds a white sub pixel, and the white sub pixel comprises a white light emitting layer, and material of the white light emitting layer comprises inorganic quantum dots. With the added white sub pixel, the luminous efficiency of the OLED is raised and the energy consumption thereof is reduced.