OLED Light-Emitting Component with Fluorescent-Phosphorescent Dual Emission
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Solution Overview
Problem
Current white organic light-emitting diodes (OLEDs) face challenges in achieving high efficiency and long lifetime, particularly due to the limited stability of blue phosphorescent emitters, which are essential for white light production, leading to short lifetimes unsuitable for practical applications.
Innovation Solution
A light-emitting component with a fluorescent emitter in the blue or blue-green spectral range and a phosphorescent emitter in a further emission layer, where the triplet energy level of the fluorescent emitter is higher than that of the phosphorescent emitter, allowing for efficient energy transfer and utilization of triplet excitons for light emission, thereby increasing efficiency and extending the component's lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If blue phosphorescent emitters are used in white OLEDs, then light efficiency is improved through utilization of triplet excitons, but lifetime is significantly reduced due to limited stability of blue phosphorescent materials
Solution Approach 1:
The emission layer is divided into two separate layers: a first emission layer containing fluorescent blue emitter and a second emission layer containing phosphorescent emitter for non-blue light. This segmentation allows each layer to use emitters optimized for their specific function, with the fluorescent layer providing long lifetime and the phosphorescent layer providing high efficiency through triplet exciton utilization.
Solution Approach 2:
The first emission layer with fluorescent blue emitter acts as an intermediary that generates triplet excitons which then transfer energy to the second emission layer containing phosphorescent emitter. This intermediary mechanism enables efficient triplet exciton utilization while avoiding direct use of unstable blue phosphorescent materials.
2Duration of action of stationary object
If fluorescent blue emitters are used, then lifetime is extended to several 10,000 hours, but light efficiency is reduced due to utilization of only 25% singlet excitons
Solution Approach 1:
The fluorescent blue emitter in the first emission layer serves as an intermediary that converts electrical energy into excitons (both singlet and triplet). While fluorescent emitters only emit from singlet states (25% efficiency), they generate triplet excitons that transfer energy to the phosphorescent emitter in the second layer, enabling overall efficiency接近100% while maintaining long lifetime.
Solution Approach 2:
The invention merges fluorescent and phosphorescent emission mechanisms in a dual-layer structure. The first layer uses fluorescent emission for blue light with long lifetime, while the second layer uses phosphorescent emission for non-blue light with high efficiency, combining the advantages of both approaches.
3Duration of action of stationary object
If phosphorescent emitters are used for green and red emission, then lifetime is improved to tens of thousands to hundreds of thousands of hours, but device complexity increases due to need for multiple emission layers and energy level matching
Solution Approach 1:
The emission region is segmented into two distinct layers with specific functions: the first layer handles blue emission and triplet exciton generation, while the second layer handles non-blue emission through phosphorescence. This segmentation simplifies the overall design by clearly defining the role of each layer and reducing the need for complex inter-layer interactions.
Solution Approach 2:
The invention changes the energy level parameters by ensuring the triplet energy level of the fluorescent blue emitter is higher than that of the phosphorescent emitter, enabling spontaneous energy transfer. This parameter optimization simplifies the device structure by eliminating the need for additional energy management components.
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 enhances the efficiency and longevity of white light emission in OLEDs, allowing for the utilization of a significant portion of triplet excitons, increasing current efficiency by a factor of 1.5 to 2 and achieving lifetimes exceeding 20,000 hours at high brightness levels.
Implementation Method 1
the emission layer comprises a fluorescent emitter which emits light predominantly in the blue or in the blue-green spectral range
Implementation Method 2
the further emission layer comprises one or a plurality of phosphorescent emitters emitting light predominantly in the non-blue spectral range
Implementation Method 3
a triplet energy for an energy level of a triplet state of the fluorescent emitter in the emission layer is greater than a triplet energy for an energy level of a triplet state of the phosphorescent emitter in the further emission layer
Data Source
AI summary
The invention relates to a light-emitting component, in particular organic light-emitting diode, having an electrode and a counterelectrode and an organic region—arranged between the electrode and the counterelectrode—with a light-emitting organic region, which comprises an emission layer and a further emission layer and which, upon application of an electrical voltage to the electrode and the counterelectrode, is formed in a manner emitting light in a plurality of colour ranges in the visible spectral range, optionally through to white light, in which case the emission layer comprises a fluorescent emitter which emits light predominantly in the blue or in the blue-green spectral range; the further emission layer comprises one or a plurality of phosphorescent emitters emitting light predominantly in the non-blue spectral range; a triplet energy for an energy level of a triplet state of the fluorescent emitter in the emission layer is greater than a triplet energy for an energy level of a triplet state of the phosphorescent emitter in the further emission layer; and an at least 5% proportion of the light generated in the light-emitting organic region is formed in the visible spectral range as fluorescent light from singlet states of the fluorescent emitter in the emission layer.