Blue OLED Emissive Layer Composition for Lower Voltage and Longer Life
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Solution Overview
Problem
Existing organic light emitting diodes (OLEDs) face challenges in achieving high luminous efficiency and luminous lifespan, particularly in blue light emitting devices, with fluorescent materials exhibiting low efficiency and phosphorescent materials having short lifespans due to the use of metal complexes.
Innovation Solution
The OLEDs incorporate a specific combination of first and second hosts in the blue emitting material layer, each being anthracene-based organic compounds, with optimized HOMO energy levels and weight ratios, minimizing energy barriers for hole injection and optimizing the emissive layer structure to enhance luminous efficiency and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent materials (metal complexes) are used to improve luminous efficiency, then luminous efficiency increases, but luminous lifespan decreases
Solution Approach 1:
The patent changes the chemical composition parameters of the emitting layer by using specific host materials (Formula 1 and Formula 3 structures) with optimized HOMO energy levels and weight ratios, enabling efficient triplet exciton utilization without metal complexes, thus achieving both high luminous efficiency and extended lifespan
Solution Approach 2:
The patent creates a composite emitting layer system combining two different host materials (Formula 1 and Formula 3 structures) with complementary properties, where the first host provides triplet exciton management and the second host provides structural stability, achieving synergistic effects that resolve the efficiency-lifespan contradiction
2Device complexity
If fluorescent materials are used to simplify the emitting layer structure, then device complexity decreases, but luminous efficiency decreases
Solution Approach 1:
The patent changes the energy level parameters of the host materials, specifically optimizing HOMO energy levels to enable effective hole injection and triplet exciton utilization, allowing fluorescent materials to achieve phosphorescent-level efficiency without requiring complex metal complex structures
3Use of energy by moving object
If blue emitting OLEDs with two hosts are used to improve luminous efficiency, then luminous efficiency increases, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the weight ratio parameter of the two host materials to a specific range (7:3 to 9:1), which simplifies the manufacturing process by providing a broad acceptable range rather than requiring precise single-point control, thereby reducing manufacturing precision requirements while maintaining high luminous 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 configuration results in reduced driving voltage, low power consumption, and improved luminous efficiency and lifespan of the OLEDs, enabling flexible and foldable display devices.
Implementation Method 1
the HOMO energy bandgap between the HOMO energy level of hole transporting material in the at least one hole transport layer or electron blocking material in the at least one electron blocking layer, and a HOMO energy level of at least one of the first host and the second host in the at least one blue emitting material layer is about 0.15 eV or less
Implementation Method 2
an organic light emitting diode (OLED) that has low power consumption, improved luminous efficiency and/or luminous lifespan
Data Source
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AI summary
An organic light emitting diode (OLED) and an organic light emitting device comprising the OLED (e.g., a display device or a lighting device) are described. The OLED can include a blue emitting material layer including plural hosts with adjusted energy levels. A HOMO energy barrier between the at least one blue emitting material layer (340) and at least one hole transport layer (320) and/or electron blocking layer (330) can be minimized. Holes generated at an anode or a P-type charge generation layer can be injected rapidly into the at least one blue emitting material layer without accumulating at an interface between the hole transport layer and/or the electron blocking layer, and the at least one blue emitting material layer. As the amount of non-emitting holes is minimized, the driving voltage of the OLED can be lowered, and the luminous efficiency and the luminous lifespan of the OLED can be improved.