Stacked Light-Emitting Element Fluorescence Phosphorescence Quenching
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Solution Overview
Problem
Existing light-emitting elements using a combination of fluorescent and phosphorescent layers face challenges in achieving high emission efficiency and stability due to quenching of phosphorescence by the fluorescent layer, leading to reduced efficiency and shorter lifetime.
Innovation Solution
A light-emitting element with a stacked-layer structure comprising a first light-emitting layer containing a host material and a fluorescent substance, and a second light-emitting layer containing organic compounds that form an exciplex and a substance that converts triplet excitation energy into luminescence, allowing for efficient emission of both fluorescence and phosphorescence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fluorescent layer is placed adjacent to a phosphorescent layer in a light-emitting element, then the device structure is simplified and fabrication is easier, but the phosphorescence is quenched by the fluorescent layer resulting in reduced emission efficiency
Solution Approach 1:
An intermediate layer is introduced between the fluorescent layer and phosphorescent layer to prevent direct interaction that causes quenching. This intermediate layer acts as a mediator that blocks the harmful energy transfer from the fluorescent layer to the phosphorescent layer, thereby maintaining high emission efficiency while still allowing the device to benefit from the simplified structure of having adjacent fluorescent and phosphorescent layers.
2Reliability
If multiple separate layers are used to achieve high emission efficiency and stability, then the light-emitting performance is improved, but the number of fabrication steps increases
Solution Approach 1:
The fluorescent layer, phosphorescent layer, and intermediate layer are combined into a single integrated light-emitting element structure that can be fabricated in one continuous process. This merging of multiple functional layers into a unified device structure maintains the high emission stability and efficiency benefits of separate layers while reducing the overall number of fabrication steps and simplifying the manufacturing process.
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 solution enables a light-emitting element with high emission efficiency, reduced power consumption, and a smaller number of fabrication steps, making it suitable for practical applications and mass production.
Implementation Method 1
light emission from the singlet excited state is referred to as fluorescence
Implementation Method 2
light emission from the triplet excited state is referred to as phosphorescence
Implementation Method 3
a substance that converts triplet excitation energy into luminescence
Data Source
AI summary
A multicolor light-emitting element that utilizes fluorescence and phosphorescence and is advantageous for practical application is provided. The light-emitting element has a stacked-layer structure of a first light-emitting layer containing a host material and a fluorescent substance and a second light-emitting layer containing two kinds of organic compounds and a substance that can convert triplet excitation energy into luminescence. Note that light emitted from the first light-emitting layer has an emission peak on the shorter wavelength side than light emitted from the second light-emitting layer.