Organic EL Light-Emitting Layer Segmentation for Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing light emitting devices face challenges in achieving high external quantum efficiency and driving durability, with previous attempts either reducing brightness or increasing driving voltage, and existing configurations fail to effectively utilize light emission from multiple units due to insulation and electrode limitations.
Innovation Solution
The light-emitting layer is divided into multiple thin layers with an intermediate charge blocking layer in between, where the thickness relationship of the layers and the use of electron or hole blocking materials enhance recombination speed and light extraction efficiency without significantly increasing driving resistance.
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 driving voltage is increased
Solution Approach 1:
The light-emitting layer is divided into multiple sub-layers (first light-emitting layer, second light-emitting layer, third light-emitting layer) with different thicknesses. This segmentation allows optimization of carrier recombination in each sub-layer, improving external quantum efficiency without requiring a barrier layer that would increase driving voltage.
Solution Approach 2:
Different regions of the light-emitting layer are assigned different thicknesses to create local quality variations. The first light-emitting layer has a first thickness, the second has a second thickness greater than the first, and the third has a third thickness greater than the second. This local differentiation optimizes carrier injection and recombination at different positions, enhancing efficiency while maintaining low driving voltage.
2Reliability
If the light-emitting layer is divided into multiple layers with different thicknesses, then recombination speed is enhanced and external quantum efficiency is improved, but device complexity increases
Solution Approach 1:
The light-emitting layer is segmented into three sub-layers with progressively increasing thicknesses from the hole transport layer side toward the electron transport layer side. This segmentation enhances recombination speed and external quantum efficiency while maintaining a relatively simple overall structure that does not significantly increase device complexity.
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 improves external quantum efficiency and driving durability by shortening the distance for charge recombination, allowing for efficient light extraction and maintaining low driving resistance, resulting in higher brightness and longer device lifespan.
Implementation Method 1
The organic EL device 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, or luminescence from excitons of other molecules produced by energy transmission from the above-described excitons.
Data Source
AI summary
In an organic EL element, a light-emitting layer is divided into at least three layers in a thickness direction including a light-emitting layer A close to an anode, a light-emitting layer C close to a cathode and a light-emitting layer B between the light-emitting layers A and C, wherein in one embodiment a thickness (a) of the light-emitting layer A, a thickness (c) of the light-emitting layer C and a thickness (b) of the light-emitting layer B satisfy the relationship of a<b<c, and an intermediate layer containing an electron blocking material is disposed between the divided light-emitting layers; and in another embodiment, the relationship of a>b>c is satisfied, and an intermediate layer containing a hole blocking material is disposed between the divided light-emitting layers.