Polymer Material for White Emission with Low Driving Voltage
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Solution Overview
Problem
Existing organic electroluminescent (EL) devices using polymer materials for white and multicolor emission suffer from high driving voltage and low light emission efficiency.
Innovation Solution
A polymer material comprising a fluorescent conjugated polymer and a phosphorescent compound, where the light emission peak wavelengths of the fluorescent conjugated polymer are less than 500 nm and those of the phosphorescent compound are not less than 500 nm, with a specific energy relation to enhance light emission efficiency and drivability at low voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a polymer material is used for white and multicolor emission in organic EL devices, then the device can manifest white color emission and multicolor emission, but the device has high driving voltage and insufficient light emission efficiency
Solution Approach 1:
The patent uses a composite polymer material combining a fluorescent conjugated polymer (emitting blue light with peak wavelength less than 500 nm) and a phosphorescent compound (emitting green to red light with peak wavelength not less than 500 nm). This composite structure enables both white and multicolor emission while improving light emission efficiency through the synergistic effect of fluorescence and phosphorescence mechanisms.
Solution Approach 2:
The patent optimizes the energy level parameters of the polymer and phosphorescent compound by enforcing the relationship (ETA-ESA0) ≥ (ETB-ESB0) - 0.2 eV, where ESA0 and ETA are the ground and excited triplet state energies of the fluorescent polymer, and ESB0 and ETB are the ground and excited triplet state energies of the phosphorescent compound. This parameter control enables efficient energy transfer and improves light emission efficiency.
2Adaptability or versatility
If a polymer material is used for white and multicolor emission in organic EL devices, then the device can manifest white color emission and multicolor emission, but the device has high driving voltage
Solution Approach 1:
The composite structure of fluorescent conjugated polymer and phosphorescent compound creates favorable energy level alignment that reduces the overall energy barrier for charge injection and recombination, thereby lowering the driving voltage required for device operation while maintaining white and multicolor emission capabilities.
Solution Approach 2:
By controlling the energy parameters (ESA0, ETA, ESB0, ETB) to satisfy the specified relationship, the patent optimizes the energy landscape of the material system, which directly influences the electrical characteristics and reduces the driving voltage needed for efficient electroluminescence.
3Loss of energy
If a phosphorescent compound with light emission peak wavelength not less than 500 nm is combined with a fluorescent conjugated polymer with light emission peak wavelength less than 500 nm, then light emission efficiency is improved, but the device complexity increases
Solution Approach 1:
The patent creates a composite material where the fluorescent conjugated polymer and phosphorescent compound are integrated at the molecular level, allowing the system to achieve improved light emission efficiency through coordinated fluorescence and phosphorescence while managing the inherent complexity through systematic material design.
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 material achieves white and multicolor emission with improved light emission efficiency and reduced driving voltage, making it suitable for practical applications in polymer LEDs.
Implementation Method 1
a fluorescent conjugated polymer (A), wherein at least one of light emission peak wavelengths of the fluorescent conjugated polymer (A) is less than 500 nm
Implementation Method 2
a phosphorescent compound (B), wherein light emission peak wavelengths of the phosphorescent compound (B) are not less than 500 nm
Data Source
AI summary
A polymer material comprising a composition containing a fluorescent conjugated polymer (A) and a phosphorescent compound (B) or comprising a polymer having the structure of (A) and the structure of (B) in the same molecule, wherein the following conditions (1), (2) and (3) are satisfied:(1) at least one of the light emission peak wavelengths of the fluorescent conjugated polymer (A) is less than 500 nm,(2) the light emission peak wavelengths of the phosphorescent compound (B) are not less than 500 nm,(3) the following relation is satisfied:ETA−ESA 0≧(ETB−ESB0)−0.2 (unit; eV) (Eq 1)(wherein, ESA 0 represents energy of the fluorescent conjugated polymer (A) at the ground state, ETA represents energy of the fluorescent conjugated polymer (A) at the lowest excited triplet state, ESB 0 represents energy of the phosphorescent compound (B) at the ground state, and ETB represents energy of the phosphorescent compound (B) at the lowest excited triplet state).