White OLED Efficiency and Stability via Mixed Phosphorescent Fluorescent Emitters
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Solution Overview
Problem
Current organic light emitting devices (OLEDs) face challenges with operational stability, particularly at high temperatures, and blue-emitting OLEDs have unsatisfactory performance, which affects the efficiency and stability of white OLEDs used in full-color displays.
Innovation Solution
The development of white OLEDs that incorporate phosphorescent materials for red and green emissions, combined with fluorescent materials for blue emission, to enhance efficiency and stability, while avoiding the short lifespan of blue phosphorescent emitters, by using a light emission zone comprising multiple layers of organic materials that include hole and electron transport materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If blue phosphorescent emitters are used in OLEDs, then red and green emission efficiency is improved, but device operational lifetime deteriorates
Solution Approach 1:
The patent changes the emission mechanism parameter from phosphorescence to fluorescence for the blue emitter, while maintaining phosphorescence for red and green emitters. This parameter change in the blue emitter's emission mechanism resolves the contradiction by achieving both high efficiency and long operational lifetime, as fluorescent blue emitters do not suffer from the short lifetime problem of phosphorescent blue emitters.
2Use of energy by moving object
If multiple phosphorescent materials are used for red and green emission, then color emission efficiency is improved, but device complexity increases
Solution Approach 1:
The patent changes the emission mechanism parameter for the blue channel from phosphorescence to fluorescence, reducing device complexity while maintaining high color emission efficiency. This parameter change simplifies the device structure by avoiding the need for phosphorescent blue materials and their associated complex requirements.
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 approach significantly improves the efficiency and stability of OLEDs, achieving high internal quantum efficiencies and extended operational lifetimes, especially for white light sources, by effectively harnessing both singlet and triplet excitons and utilizing a combination of phosphorescent and fluorescent emitters.
Implementation Method 1
a light emitting region comprising one or more phosphorescent materials that emit red light, one or more phosphorescent materials that emit green light
Implementation Method 2
one or more fluorescent materials that emit blue light
Implementation Method 3
under an electric field, positive charges (holes) and negative charges (electrons) are respectively injected from the anode and cathode into the luminescent material and undergo recombination to form excitonic states which subsequently emit light
Data Source
AI summary
A white organic light emitting device includes an anode; a cathode; and a light emitting region comprising one or more phosphorescent materials that emit red light, one or more phosphorescent materials that emit green light, and one or more fluorescent materials that emit blue light.