Stacked-Layer Light-Emitting Element Carrier Balance Compensation
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Solution Overview
Problem
Conventional light-emitting elements with organic compounds face challenges in maintaining favorable characteristics over long-time driving due to changes in carrier balance and light-emitting region shifts, leading to short lifetimes and reduced utility.
Innovation Solution
A light-emitting element with a stacked-layer structure comprising different light-emitting materials, where a light-emitting layer with a short wavelength is sandwiched between layers with the same emission color, compensating for changes in carrier balance and maintaining stable emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional light-emitting element structure is used, then the element can be manufactured with simpler structure, but the element cannot maintain favorable characteristics over long-time driving due to carrier balance changes and light-emitting region shifts
Solution Approach 1:
The light-emitting layer is divided into multiple sub-layers (first light-emitting layer, second light-emitting layer, third light-emitting layer) with different light-emitting materials. Each sub-layer has specific emission characteristics that work together to maintain stable overall emission, preventing the light-emitting region shift problem in conventional single-layer structures.
Solution Approach 2:
Different regions of the light-emitting layer are assigned different materials with specific emission wavelengths. The first and third light-emitting layers use materials emitting at a first wavelength, while the second light-emitting layer uses materials emitting at a second wavelength, creating local emission characteristics that compensate for carrier balance changes.
2Reliability
If light-emitting materials with different emission characteristics are used in stacked layers, then carrier balance changes can be compensated and stable emission maintained, but the manufacturing process becomes more complex
Solution Approach 1:
The invention changes the emission wavelength parameter across different light-emitting layers. By selecting materials with specific emission characteristics (first wavelength for outer layers, second wavelength for middle layer), the structure compensates for carrier balance changes and maintains stable emission, accepting increased manufacturing complexity as a trade-off for reliability.
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 ensures that the light-emitting element retains favorable characteristics over long-time driving, extending its lifetime and improving reliability by compensating for shifts in the light-emitting region through the use of a stacked-layer structure with specific light-emitting materials.
Implementation Method 1
a light-emitting element including an EL layer including at least a light-emitting layer between a pair of electrodes. The light-emitting layer includes a light-emitting material, a hole-transport material, and an electron-transport material
Data Source
AI summary
A light-emitting element with high reliability that can keep favorable characteristics after long-time driving is provided. In addition, a light-emitting device having a long lifetime including the light-emitting element is provided. Moreover, an electronic device and a lighting device having a long lifetime are provided. In a light-emitting element including an EL layer between a pair of electrodes, a light-emitting layer included in the EL layer has a stacked-layer structure which is different from the conventional structure, whereby the light-emitting element can keep favorable characteristics after long-time driving even in the case where carrier balance is changed over time due to driving of the light-emitting element or a light-emitting region is shifted due to the change.