Light-Emitting Device Composite Emission Layer Driving Voltage
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Solution Overview
Problem
Conventional light-emitting devices face challenges in achieving low driving voltage and high efficiency due to high resistance in the emission layer, which complicates charge balance and lifespan characteristics.
Innovation Solution
Incorporating a first compound and a second compound in the emission layer, where the first compound facilitates hole transport and reduces hole trapping through its amine-based characteristics, and the second compound enhances electron transport by controlling the LUMO energy level, thereby reducing driving voltage and improving efficiency and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-host system is used in the emission layer, then the device structure is simple, but the resistance is high and efficiency is low
Solution Approach 1:
The emission layer uses a composite host system comprising a first host compound and a second host compound in specific weight ratios (95:5 to 5:95). The first host compound has electron-transporting characteristics with LUMO energy level of -2.0 eV to -3.0 eV, while the second host compound has hole-transporting characteristics with HOMO energy level of 5.5 eV to 6.5 eV. This composite material approach reduces resistance and improves efficiency while maintaining controlled device complexity.
2Device complexity
If conventional emission layer materials are used, then the device structure is simple, but charge balance is poor and lifespan is short
Solution Approach 1:
The invention optimizes specific energy level parameters of the host compounds to improve charge balance and lifespan. The first host compound has LUMO energy level of -2.0 eV to -3.0 eV for efficient electron transport, while the second host compound has HOMO energy level of 5.5 eV to 6.5 eV for efficient hole transport. The weight ratio of the two compounds is controlled at 95:5 to 5:95, achieving optimal charge balance and extended device lifespan.
3Ease of manufacture
If high resistance materials are used in the emission layer, then manufacturing is easier, but efficiency is low and driving voltage is high
Solution Approach 1:
The emission layer employs a composite system of two host compounds with complementary transport characteristics. The first host compound (electron-transporting, LUMO: -2.0 to -3.0 eV) and second host compound (hole-transporting, HOMO: 5.5 to 6.5 eV) work synergistically to reduce resistance and improve efficiency. This composite approach maintains ease of manufacture through conventional fabrication processes while achieving high 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
The use of these compounds in the light-emitting device results in reduced driving voltage, high efficiency, and extended lifespan by effectively controlling hole and electron transport, addressing the limitations of single-host systems.
Implementation Method 1
the first compound facilitates hole transport and reduces hole trapping through its amine-based characteristics
Implementation Method 2
the second compound enhances electron transport by controlling the LUMO energy level
Implementation Method 3
Carriers, such as holes and electrons, recombine in the emission layer to produce excitons. These excitons transit from an excited state to a ground state to thereby generate light.
Data Source
AI summary
A light-emitting device includes: a first electrode; a second electrode facing the first electrode; and an interlayer between the first electrode and the second electrode, wherein the interlayer includes an emission layer, and the emission layer includes a first compound of Formula 1-1 or Formula 1-2 and a second compound of Formula 2, as described herein.