Organic EL Layer Structure for Low-Voltage Long-Life Emission
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing light-emitting devices, particularly organic electroluminescent (EL) elements, face challenges in achieving high emission efficiency, long lifetime, low driving voltage, and high reliability while maintaining low power consumption.
Innovation Solution
The light-emitting device incorporates a specific layered structure comprising an anode, cathode, and an EL layer with multiple organic compound layers, including a first layer with an electron-accepting property, a light-emitting layer with an emission center substance, and other layers with controlled HOMO and LUMO levels, electron mobility, and hole-transport skeletons to optimize carrier injection and recombination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional light-emitting device structures are used, then basic light emission is achieved, but emission efficiency and lifetime are insufficient
Solution Approach 1:
The device is divided into multiple functional layers including hole injection layer, hole transport layer, light-emitting layer, electron transport layer, and electron injection layer. Each layer is optimized independently with specific organic compounds to achieve both high emission efficiency and long lifetime through specialized material selection and structure design.
Solution Approach 2:
The patent employs composite organic compound structures within each layer, combining materials with complementary properties (e.g., hole-transporting and electron-transporting materials in the light-emitting layer) to achieve synergistic effects that simultaneously improve emission efficiency and device stability for extended lifetime.
2Productivity
If high emission efficiency is pursued, then more carriers are injected, but driving voltage increases
Solution Approach 1:
Different layers are assigned specific organic compounds with tailored energy levels and transport properties optimized for their local function. The hole injection layer uses compounds with deep HOMO levels, while the electron transport layer uses compounds with shallow LUMO levels, creating local optimization that reduces overall driving voltage while maintaining high emission efficiency.
Solution Approach 2:
The patent systematically adjusts key parameters including HOMO levels of hole-transport materials (−5.7 to −5.2 eV), LUMO levels of electron-transport materials (−2.5 to −1.5 eV), and electron mobilities (1×10⁻⁷ to 5×10⁻⁵ cm²/Vs) to optimize the balance between emission efficiency and driving voltage through precise material selection.
3Productivity
If multiple organic compounds are used to optimize performance, then emission efficiency improves, but device complexity increases
Solution Approach 1:
The light-emitting layer contains both hole-transporting and electron-transporting organic compounds that simultaneously perform multiple functions: charge transport, recombination facilitation, and light emission. This multi-functionality reduces the need for separate dedicated layers, simplifying the overall device structure while maintaining high emission efficiency.
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 structure enhances emission efficiency, extends device lifetime, reduces power consumption, and improves reliability by optimizing carrier injection and recombination, resulting in improved performance characteristics.
Implementation Method 1
Light-emitting devices (organic EL elements) including organic compounds and utilizing electroluminescence (EL) have been put to more practical use. Carriers are injected by application of voltage to the element, and recombination energy of the carriers is used, whereby light emission can be obtained from the light-emitting material.
Data Source
AI summary
A light-emitting device including an EL layer including a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in this order from the anode side is provided. The first layer contains a first organic compound and a second organic compound. The light-emitting layer contains a sixth organic compound. The fourth layer contains a seventh organic compound. The first organic compound exhibits an electron-accepting property with respect to the second organic compound. A HOMO level of the second organic compound is higher than or equal to −5.7 eV and lower than or equal to −5.2 eV. A HOMO level of the third organic compound is equal to or deeper than the HOMO level of the second organic compound. A difference between the HOMO levels of the second organic compound and the third organic compound is less than or equal to 0.2 eV.