Hybrid OLED with Quantum Dot Microlens Array for Light Extraction
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Solution Overview
Problem
Conventional OLEDs face inefficiencies and short lifetimes in producing 'warm' white light, with limited color control and low light extraction efficiency, failing to meet the DOE SSL 2015 Multi-year Program Goals for luminance and Color Rendering Index (CRI) requirements.
Innovation Solution
A hybrid OLED device incorporating a blue or blue-green electroluminescent layer with photoluminescent quantum dots (QDs) for down-conversion of blue and green light to achieve white light emission, utilizing QDs dispersed in an optical resin and integrated into a microlens array on the light exiting face to enhance light extraction and color rendering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional OLEDs are used to produce warm white light, then ease of manufacture and flexibility are improved, but luminous efficiency and lifetime deteriorate
Solution Approach 1:
The patent combines organic OLED materials with inorganic quantum dot materials to create a hybrid device. The OLED layer provides flexibility and ease of manufacture, while the quantum dot conversion layer provides stable, efficient light conversion. This composite structure allows the device to maintain the manufacturing advantages of OLEDs while achieving the stability and efficiency of inorganic quantum dots.
2Ease of manufacture
If conventional OLEDs use broad emission spectra, then ease of manufacture is improved, but color rendering quality deteriorates
Solution Approach 1:
The patent applies local quality by placing quantum dots with specific size and composition in the conversion layer to target particular wavelength ranges. By controlling the size and material composition of quantum dots at specific locations in the conversion layer, the device achieves precise color rendering control in the red and green regions while maintaining the simplicity of OLED fabrication.
3Manufacturing precision
If quantum dots are added to convert blue light to white light, then color rendering is improved, but device complexity increases
Solution Approach 1:
The patent segments the light conversion function into a separate quantum dot conversion layer distinct from the OLED emissive layer. This segmentation allows the OLED to focus on generating blue light efficiently while the quantum dot layer handles the wavelength conversion to red and green, simplifying the design of each component while achieving superior overall color rendering.
4Loss of energy
If light extraction enhancement methods are applied, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The patent introduces a microlens array as an intermediary optical element between the OLED layer and the quantum dot conversion layer. This microlens array serves dual functions: it enhances light extraction from the OLED by redirecting waveguided modes, and it improves the coupling of blue light into the quantum dots for efficient down-conversion, thereby addressing multiple optical challenges with a single intermediate component.
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 hybrid OLED achieves high luminous efficiency and CRI, exceeding 100 lm/W and reaching a CRI of 91, with improved light extraction and color quality, effectively producing 'warm' white light while addressing the limitations of conventional OLEDs.
Implementation Method 1
a conversion layer that contains photoluminescent quantum dots (QDs) at or near the light exiting face of the hybrid OLED. The QDs are of a quantity and density to down-convert a portion of the blue and green light to one or more higher wavelengths of visible light
Data Source
AI summary
A white light source is a hybrid organic light emitting diode (OLED) device having an electroluminescent layer including a blue emitting organic phosphor or a combination of a green emitting organic phosphor with a blue emitting phosphor and a conversion layer including photoluminescent quantum dots (QDs) at or near the light exiting face of the hybrid OLED. The QDs down-convert a portion of the blue or blue and green light to higher wavelengths of visible light, where the combination of wavelengths exiting the device provides white light. The QDs can be within an array of microlenses on the light exiting surface of the hybrid OLED to enhance the efficiency of light emission from the electrically excited phosphors and the down-conversion QDs.