Single Mixed-Color Emitting Layer for White Light
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Solution Overview
Problem
Conventional organic EL devices require multiple emitting layers to produce white light, leading to complex manufacturing processes and high costs, with challenges in achieving balanced color emission due to energy transfer issues between dopants, resulting in reduced device lifetime.
Innovation Solution
An organic EL device with a single mixed-color emitting layer containing a fluorescent dopant for blue emission and a phosphorescent dopant for green and red emission, where the energy gaps are optimized to prevent energy transfer between the dopants, allowing for efficient fluorescent and phosphorescent emissions without thinning the exciton-generating layer, thereby maintaining device lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple emitting layers are used to produce white light, then color balance is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines multiple emitting layers into a single mixed-color emitting layer that contains both fluorescent and phosphorescent dopants. This merging approach maintains the color balance advantage of multiple layers while eliminating the complexity of layering and alignment processes, achieving white light emission from a single unified layer.
Solution Approach 2:
The single mixed-color emitting layer performs multiple functions simultaneously: it generates both fluorescent and phosphorescent emissions, achieves color balance, and eliminates the need for separate emitting layers. This multi-functionality resolves the contradiction by making one layer do the work of multiple layers.
2Illumination intensity
If dopant concentrations are adjusted to balance color emission, then color balance is improved, but manufacturing difficulty increases
Solution Approach 1:
The patent changes the energy gap parameter of the host material to resolve color balance issues. By selecting a host with an appropriate energy gap (2.1-3.5 eV), the system achieves balanced color emission without requiring precise adjustment of dopant concentrations, thereby simplifying manufacturing.
Solution Approach 2:
The host material acts as an intermediary that mediates between the fluorescent and phosphorescent dopants. By controlling the host's energy gap, the system achieves color balance through the host's energy transfer properties rather than through complex dopant concentration adjustments.
3Power
If the fluorescent-emitting layer is thinned to enable triplet energy transfer, then phosphorescent emission is improved, but device lifetime decreases
Solution Approach 1:
The patent extracts the phosphorescent dopant from a separate phosphorescent-emitting layer and places it within the mixed-color emitting layer alongside the fluorescent dopant. This extraction eliminates the need for thinning the fluorescent layer to enable energy transfer, as the triplet energy transfer occurs within the same layer where the phosphorescent dopant resides, preserving device lifetime while maintaining phosphorescent emission.
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 enables the production of white light with balanced color emission using a single emitting layer, simplifying manufacturing and reducing costs while extending the device's lifetime by utilizing both fluorescent and phosphorescent emissions efficiently.
Implementation Method 1
a fluorescent dopant for fluorescent emission
Implementation Method 2
a phosphorescent dopant for phosphorescent emission
Data Source
AI summary
An organic EL device (1) includes an anode (3), a cathode (4) and an organic thin-film layer (5) provided between the anode (3) and the cathode (4). The organic thin-film layer (5) includes a single-layered mixed-color emitting layer (51) for providing mixed-color emission. The mixed-color emitting layer (51) contains a host, a fluorescent dopant for blue fluorescent emission and a phosphorescent dopant for red or green phosphorescent emission.