Light Emitting Layer Host Composition for Efficiency and Lifespan
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Solution Overview
Problem
Existing light emitting devices face challenges in achieving high efficiency and longevity due to variations in efficiency and lifespan of light emitting materials based on wavelength, along with issues related to parasitic capacitance and threshold voltage fluctuations.
Innovation Solution
A light emitting device design incorporating a first electrode, a second electrode, an electron blocking layer, a first light emitting layer with a p-type host, a first n-type host, a second n-type host, and a dopant, where the LUMO energy level of the first n-type host is higher than that of the second n-type host, and the hole mobility of the first n-type host is greater than the second n-type host but less than the p-type host, to maintain optimal hole-electron balance and increase capacitance threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If light emitting materials with different wavelengths are used to express color, then color expression capability is improved, but efficiency and lifespan of the light emitting device vary
Solution Approach 1:
The patent applies local quality by using different host materials (first n-type host and second n-type host with different LUMO energy levels and hole mobilities) in the same light emitting layer to optimize performance for specific wavelength emissions. This allows the device to maintain high efficiency and lifespan for the intended color while still supporting multiple color expressions through the dopant system.
2Reliability
If parasitic capacitance in the intermediate layer is reduced, then device reliability is improved, but threshold voltage fluctuations occur
Solution Approach 1:
The patent applies parameter changes by carefully selecting and adjusting the LUMO energy levels and hole mobilities of the host materials in the light emitting layer. By optimizing these parameters, the device achieves reduced parasitic capacitance while maintaining stable threshold voltage, as the energy level alignment controls both capacitance and voltage characteristics simultaneously.
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 enhances luminous efficacy, reduces driving voltage, and extends the lifespan of the device by stabilizing the capacitance threshold voltage, thereby improving reliability and efficiency.
Implementation Method 1
light emitting devices use light emitting materials that emit light with different wavelengths for expressing color
Data Source
AI summary
A light emitting device can include a first electrode and a second electrode facing each other, and an electron blocking layer, a first light emitting layer, and an electron transport layer between the first electrode and the second electrode. The first light emitting layer can include a p-type host, a first n-type host, a second n-type host, and a dopant, a LUMO energy level of the first n-type host is higher than a LUMO energy level of the second n-type host. A hole mobility of the first n-type host can be greater than a hole mobility of the second n-type host and can be smaller than a hole mobility of the p-type host.