Stacked Organic Layers for Light-Emitting Element Luminance Stability
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Solution Overview
Problem
Existing light-emitting elements experience significant luminance degradation over time, limiting their practical application due to insufficient measures addressing the causes of luminance decrease.
Innovation Solution
A light-emitting element structure with specific layer configurations, including stacked organic compound layers and a hole-transporting layer, where the proportion and properties of organic compounds are optimized to minimize luminance loss and facilitate color control, using materials like anthracene derivatives with wide band gaps as host materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional light-emitting element structures are used, then device simplicity is maintained, but luminance degradation occurs over time
Solution Approach 1:
The light-emitting element is divided into multiple functional layers with distinct purposes: a first light-emitting layer containing a first emission center substance, a second light-emitting layer containing a second emission center substance, and a hole-transporting layer. This segmentation allows each layer to be optimized for its specific function, improving overall luminance stability while managing complexity through functional specialization.
Solution Approach 2:
Different regions of the device are assigned different materials and functions. The first light-emitting layer uses a first emission center substance optimized for its emission characteristics, while the second light-emitting layer uses a second emission center substance with different properties. The hole-transporting layer is specifically positioned to manage carrier transport. This local optimization of material properties at different locations improves luminance stability without requiring complete redesign of the entire structure.
2Adaptability or versatility
If multiple emission center substances are stacked to achieve color variations, then emission color control is improved, but device complexity increases
Solution Approach 1:
The emission function is segmented across multiple layers, with each light-emitting layer containing a specific emission center substance that contributes to the overall emission spectrum. This allows independent optimization of each layer's emission characteristics while maintaining a systematic structure that manages complexity through functional division.
Solution Approach 2:
The stacked structure serves multiple functions simultaneously: it generates different emission colors from different layers, enables color mixing to achieve white light or other desired colors, and maintains a systematic architecture that facilitates manufacturing. The hole-transporting layer provides both charge transport and structural organization, demonstrating multi-functionality that reduces overall device complexity.
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 proposed structure significantly reduces luminance degradation over time, enhances reliability, and allows for easy control of emission colors, particularly in white light-emitting elements.
Implementation Method 1
a layer which contains an organic compound and is located between the first electrode and the second electrode... light emission is obtained by current flowing between the pair of electrodes
Implementation Method 2
by stacking of layers containing an emission center substance which exhibits different emission colors, light emission overlap, and more variations of emission colors can be obtained. In particular, the emphasis is put on white light which can be obtained by overlapping of red light, green light, and blue light
Data Source
AI summary
A light-emitting element whose degree of deterioration with driving time is improved and of which emission colors are easily controlled. A light-emitting emitting element having a first electrode, a second electrode, and a layer containing an organic compound located between the first electrode and the second electrode, in which the layer containing the organic compound at least has, from the second electrode side, a light-emitting layer in which a first layer, a second layer, and a third layer are stacked, and a hole-transporting layer provided in contact with the third layer; the first layer contains a first organic compound and a second organic compound; the second layer contains a third organic compound and a fourth organic compound; and the third layer contains the first organic compound and a fifth organic compound.