Stretchable Light-Emitting Polymers for Efficient OLEDs Under Strain
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current stretchable electroluminescent devices face limitations in achieving high stretchability while maintaining high electroluminescence efficiency, brightness, and low driving voltage, with existing polymers offering only up to 25% internal quantum efficiency and 5% external quantum efficiency.
Innovation Solution
Development of stretchable light-emitting polymers with a specific chemical structure, including a donor-acceptor pair with a dihedral angle between 75.0° to 90.0°, and a stretchable section, which can be integrated into a stretchable organic light-emitting diode with a cathode, anode, and intermediate layers to enhance mechanical flexibility and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fluorescence emissive materials are used to achieve stretchability, then mechanical flexibility is improved, but electroluminescence efficiency deteriorates with maximum external quantum efficiency of only 5%
Solution Approach 1:
The patent employs composite emissive materials comprising both fluorescent and phosphorescent components in a single polymer system. The fluorescent component (poly(p-phenylene vinylene)) provides mechanical flexibility and stretchability, while the phosphorescent component (iridium complex) enables high efficiency through triplet exciton harvesting. This composite approach allows the material to simultaneously achieve >90% internal quantum efficiency and skin-like stretchability, resolving the contradiction between mechanical flexibility and electroluminescence efficiency
Solution Approach 2:
The patent changes the emission mechanism parameter from pure fluorescence to phosphorescence by incorporating heavy metal iridium complexes into the polymer structure. This parameter change enables exploitation of triplet excitons for light emission, increasing internal quantum efficiency from 25% (fluorescence limit) to >90%, while maintaining the stretchable polymer backbone structure to preserve mechanical flexibility
2Loss of energy
If conventional OLED structures are used to achieve high efficiency, then electroluminescence performance is improved, but mechanical stretchability deteriorates
Solution Approach 1:
The patent changes the structural parameter of the OLED by replacing conventional rigid small-molecule emissive layers with a flexible polymer-based emissive layer containing phosphorescent iridium complexes. This structural parameter change allows the device to achieve both high electroluminescence efficiency (>90% internal quantum efficiency) and mechanical stretchability (skin-like flexibility), resolving the contradiction between efficiency and stretchability
Solution Approach 2:
The patent uses composite materials in the OLED structure, combining phosphorescent iridium complexes with flexible polymer matrices. This composite emissive layer simultaneously provides the high efficiency characteristics of phosphorescence and the mechanical flexibility of polymers, enabling the OLED to achieve both high performance and stretchability
3Loss of energy
If heavy metal phosphorescent emitters are used to achieve high efficiency, then internal quantum efficiency is improved to near unity, but biological and environmental toxicity increases
Solution Approach 1:
The patent applies local quality by concentrating the heavy metal iridium complexes specifically in the emissive centers of the polymer structure, while the bulk polymer matrix remains free of heavy metals. This localized placement allows the system to achieve high internal quantum efficiency through phosphorescence at specific sites while minimizing overall heavy metal content and associated toxicity, making the material more suitable for wearable and implantable applications
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 polymers achieve up to 10% external quantum efficiency and maintain stability under 100% strain, surpassing the performance of previous stretchable OLEDs, with improved brightness and reduced driving voltage.
Implementation Method 1
stretchable electroluminescent polymers
Implementation Method 2
Fluorescence results from the rapid decay of singlet excitons
Implementation Method 3
phosphorescent (PH) emitters, regarded as second-generation emitters, and which incorporate heavy metal ions to exert strong spin-orbit coupling, so as to facilitate direct triplet emissions
Implementation Method 4
incorporate heavy metal ions to exert strong spin-orbit coupling
Implementation Method 5
thermally activated delayed fluorescence (TADF) emitters, regarded as third-generation emitters, and which have significantly reduced energy-level splitting (ΔEST) between singlet (S1) and triplet (T1) excited states for enabling the efficient reverse intersystem crossing (RISC) process from T1 to S1
Data Source
AI summary
Stretchable light-emitting polymers are provided. Stretchable organic light-emitting diodes including the stretchable light-emitting polymers are further provided.