Organic Electroluminescence Element Concentration Gradient
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Solution Overview
Problem
Organic electroluminescence elements face challenges in achieving high light-emission efficiency and durability, with existing solutions either compromising on brightness, drive durability, or not effectively utilizing the entire light-emitting layer.
Innovation Solution
An organic electroluminescence element with a light-emitting layer containing two electron transporting materials and a hole transporting host material, where the concentration of these materials decreases from the cathode to the anode, optimizing the emission spectrum and layer structure for enhanced efficiency and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a barrier layer is disposed between the light-emitting layer and hole transport layer to control carrier migration balance, then external quantum efficiency is enhanced, but brightness is lowered and drive durability is reduced
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of electron transporting materials within the light-emitting layer, where the concentration is higher near the cathode interface and lower near the anode interface. This spatial variation in material concentration optimizes carrier migration balance locally throughout the layer, enhancing external quantum efficiency without requiring a barrier layer that would reduce brightness and durability.
2Reliability
If a barrier layer is disposed between the light-emitting layer and hole transport layer to control carrier migration balance, then external quantum efficiency is enhanced, but drive durability is reduced
Solution Approach 1:
The patent uses local quality by implementing a concentration gradient of electron transporting materials in the light-emitting layer, with higher concentration near the cathode and lower concentration near the anode. This gradual transition optimizes carrier migration balance throughout the layer, improving external quantum efficiency without the durability penalties associated with discrete barrier layers.
3Device complexity
If light emitting units are stacked in a multi-layer structure with insulating layers, then device complexity is reduced, but light extraction is hindered and external quantum efficiency is not improved
Solution Approach 1:
The patent applies parameter changes by modifying the concentration parameter of electron transporting materials within the light-emitting layer. By varying the concentration from high near the cathode to low near the anode, the patent optimizes carrier migration and recombination processes, achieving high external quantum efficiency without requiring complex multi-layer stacking structures with insulating layers.
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 solution achieves high light-emission efficiency across a wide current range while maintaining durability, allowing for uniform light emission across the entire light-emitting layer and improved drive durability.
Implementation Method 1
The organic EL element is a device for obtaining luminescence by utilizing at least either one of luminescence from excitons each of which is obtained by recombining an electron injected from a cathode with a hole injected from an anode to produce the exciton in the light-emitting layer, or luminescence from excitons of other molecules produced by energy transmission from at least one of the above-described excitons.
Data Source
AI summary
The present invention provides an organic electroluminescence element having at least a light-emitting layer disposed between a pair of electrodes, wherein the light-emitting layer includes at least two electron transporting materials and a hole transporting host material, with at least one of the electron transporting materials being an electron transporting light-emitting material, and a total concentration of the at least two electron transporting materials in the light-emitting layer decreases from a cathode side toward an anode side.