Light Emitting Polymer with Phosphorescence and Fluorescence Units
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Solution Overview
Problem
Current organic light emitting devices using fluorescent compounds have low light emitting efficiency due to wastage of triplet excitons, while phosphorescent compounds offer 100% internal quantum efficiency but require improvement in color purity and lifetime, especially for blue light emission.
Innovation Solution
A light emitting polymer incorporating both phosphorescence and fluorescence units, represented by a specific formula, which enables simultaneous emission of multiple colors, thereby achieving high luminance, efficiency, and long lifetime, and the ability to emit white light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fluorescent compound is used to form an emissive layer, then the device structure is simple, but triplet excitons are wasted resulting in low light emitting efficiency
Solution Approach 1:
The patent uses a composite material approach by combining fluorescent and phosphorescent compounds in a single emissive layer. The fluorescent compound provides structural simplicity while the phosphorescent compound enables triplet exciton utilization. This composite system resolves the contradiction by integrating multiple material functions into one layer, achieving both simplicity and high efficiency.
2Use of energy by moving object
If a phosphorescent compound is used to form an emissive layer, then internal quantum efficiency reaches 100%, but color purity and lifetime need improvement
Solution Approach 1:
The patent applies local quality by assigning different functional roles to different compounds within the emissive layer. The phosphorescent compound specifically addresses efficiency by utilizing triplet excitons, while the fluorescent compound contributes to color purity and device stability. Each material is optimized for its specific function, resolving the contradiction between efficiency and reliability.
Solution Approach 2:
The patent changes the compositional parameters of the emissive layer by using specific ratios of fluorescent to phosphorescent compounds (e.g., 95:5 to 50:50 by weight). This parameter optimization allows the system to achieve high internal quantum efficiency while maintaining good color purity and lifetime characteristics through careful tuning of material proportions.
3Use of energy by moving object
If blue phosphorescent materials are used, then high efficiency is achieved, but lifetime is insufficient
Solution Approach 1:
The fluorescent compound acts as an intermediary that mitigates the degradation issues of blue phosphorescent materials. While the phosphorescent compound provides high efficiency through triplet exciton utilization, the fluorescent compound contributes to device stability and extends lifetime. The intermediary fluorescent material protects against the inherent instability of blue phosphorescent emitters.
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 polymer achieves high internal quantum efficiency, long lifetime, and excellent luminance, with stable white light emission, improving upon the limitations of single-emission mechanisms by utilizing both phosphorescent and fluorescent mechanisms.
Implementation Method 1
a phosphorescence unit (M(L)t) wherein M is a bivalent to tetravalent metal atom, L is an organic ligand, and t is 1 or 2
Implementation Method 2
a fluorescence unit
Data Source
AI summary
A light emitting polymer includes a phosphorescence unit and a fluorescence unit. An organic light emitting device includes the light emitting polymer. The light emitting polymer can emit light of two or more colors according to a phosphorescent and fluorescent mechanisms, and thus the organic light emitting device including the light emitting polymer can have long lifetime, high brightness and excellent efficiency, and emit white light.