Blue Light Emitting Device Efficiency-Improving Layer
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Solution Overview
Problem
Light emitting devices face a trade-off between efficiency and lifespan due to the consumption of holes in the light emitting layer, where triplet-triplet fusion methods improve efficiency but deteriorate the electron-blocking layer, reducing lifespan.
Innovation Solution
Incorporating an efficiency-improving layer with a bipolar host and a second blue light emitting dopant adjacent to the light emitting layer, which utilizes surplus holes for auxiliary light emission, thereby reducing electron transport layer deterioration and enhancing lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If triplet-triplet fusion method is used to improve efficiency, then luminous efficiency is improved, but electron-blocking layer deteriorates and lifespan is reduced
Solution Approach 1:
The device is segmented into two distinct light emitting layers: a first light emitting layer using triplet-triplet fusion for high efficiency, and a second light emitting layer serving as an electron-blocking layer to prevent deterioration. This segmentation allows each layer to specialize in one function, resolving the contradiction between efficiency and lifespan.
Solution Approach 2:
The first light emitting layer acts as an intermediary that performs the high-efficiency light emission through triplet-triplet fusion, while the second light emitting layer protects the electron-blocking layer from deterioration. The intermediary layer absorbs the harmful effects, allowing the system to achieve both high efficiency and long lifespan.
2Object-generated harmful factors
If holes are consumed in the light emitting layer for light emission, then light emission function is achieved, but efficiency is limited due to hole consumption
Solution Approach 1:
Holes that would otherwise be consumed and lost in the first light emitting layer are recovered and utilized in the second light emitting layer for additional light emission. This discarding and recovering process converts waste holes into useful light output, improving overall efficiency while maintaining the light emission function.
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 both efficiency and lifespan by inducing auxiliary light emission and preventing electron-blocking layer deterioration, effectively addressing the trade-off between efficiency and lifespan in blue light emitting devices.
Implementation Method 1
a light emitting device includes a first electrode and a second electrode facing each other, and a hole transport layer, a light emitting layer, an efficiency-improving layer, and an electron transport layer sequentially stacked between the first electrode and the second electrode
Implementation Method 2
A blue fluorescent device improves efficiency using a triplet-triplet fusion (TTF) method
Data Source
AI summary
Disclosed are a light emitting device that includes an additional layer adjacent to a light emitting layer and thus is capable of utilizing, in light emission, holes not used in the light emitting layer, to improve efficiency and lifespan, and a light emitting display device including the same. The light emitting device includes a first electrode and a second electrode facing each other, and an unit comprising a hole transport layer, a light emitting layer, an efficiency-improving layer, and an electron transport layer sequentially stacked between the first electrode and the second electrode, wherein the light emitting layer includes a first host comprising an anthracene derivative and a first blue light emitting dopant, and the efficiency-improving layer includes a second host having bipolarity and a second blue light emitting dopant.