Organic Light-Emitting Layer Composition for Low-Capacitance Displays
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Solution Overview
Problem
There is a persistent demand for organic electroluminescence elements with low driving voltage and improved image quality in display devices.
Innovation Solution
A light-emitting element comprising a first electrode, a second electrode, and a light-emitting layer with specific host compounds and phosphorescent and fluorescent compounds, where at least one of the host compounds has a lower work function than the phosphorescent compound, and includes a hole transport region and electron transport region with compounds having positive or negative work functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a phosphorescent compound with positive giant surface potential is used in the light-emitting layer, then the device achieves stable light emission, but the capacitance increases and driving voltage remains high
Solution Approach 1:
The patent changes the giant surface potential parameter of the host compounds from positive to negative values. Specifically, the hole-transporting host compound has a giant surface potential of -0.5 to -2.0 V and the electron-transporting host compound has -0.3 to -1.8 V, while the phosphorescent compound maintains its positive giant surface potential of +0.5 to +2.0 V. This parameter inversion reduces capacitance while maintaining stable light emission.
Solution Approach 2:
The patent creates a composite light-emitting layer containing four types of compounds with complementary properties: hole-transporting host compound, electron-transporting host compound, phosphorescent compound, and fluorescent compound. This composite structure balances charge transport, reduces capacitance, and maintains emission stability through synergistic interactions between the different materials.
2Device complexity
If conventional host compounds are used in the light-emitting layer, then the device structure is simple, but the driving voltage is high and image quality is insufficient
Solution Approach 1:
The patent specifies precise giant surface potential ranges for each compound type: hole-transporting host (-0.5 to -2.0 V), electron-transporting host (-0.3 to -1.8 V), phosphorescent compound (+0.5 to +2.0 V), and fluorescent compound (+0.3 to +1.5 V). These controlled parameter changes enable lower driving voltage while maintaining a relatively simple four-component light-emitting layer structure.
3Reliability
If the giant surface potential of host compounds is higher than that of phosphorescent compound, then charge injection is improved, but capacitance increases and energy consumption rises
Solution Approach 1:
The patent inverts the conventional approach by making the host compounds have negative giant surface potentials lower than the phosphorescent compound's positive potential. The hole-transporting host has -0.5 to -2.0 V and electron-transporting host has -0.3 to -1.8 V, while phosphorescent compound has +0.5 to +2.0 V. This inversion maintains charge injection efficiency while reducing capacitance and energy consumption.
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 low capacitance characteristics and improved image quality in display devices.
Implementation Method 1
a phosphorescent compound, and a fluorescent compound
Implementation Method 2
a phosphorescent compound, and a fluorescent compound
Implementation Method 3
an organic electroluminescence element in which holes and electrons respectively injected from a first electrode and a second electrode recombine in a light-emitting layer
Data Source
AI summary
Embodiments provide a light-emitting element and a display device that includes the light-emitting element. The light-emitting element includes a first electrode, a second electrode disposed on the first electrode, and a light-emitting layer disposed between the first electrode and the second electrode. The light-emitting layer includes a hole-transporting host compound, an electron-transporting host compound, a phosphorescent compound, and a fluorescent compound, wherein at least one of the hole-transporting host compound and the electron-transporting host compound has a lower giant surface potential than the phosphorescent compound.