Tandem-Carbene Phosphors for Tunable OLED Color Emission
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing organic light emitting diodes (OLEDs) face challenges in achieving efficient and tunable emission colors, particularly in producing saturated red, green, and blue pixels for full color displays.
Innovation Solution
A compound comprising a first ligand and a second ligand, where the first ligand coordinates to a first metal through a metal-carbene bond, and the second ligand coordinates to a second metal and also to the first metal, forming a multidentate ligand. This compound is used in an organic layer of an OLED, allowing for the tuning of emission colors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional phosphorescent emissive molecules are used in OLEDs, then the device can achieve light emission, but the emission color cannot be easily tuned to produce saturated red, green, and blue pixels
Solution Approach 1:
The patent applies parameter changes by systematically varying the ligand structures coordinated to the iridium metal center. By changing the chemical composition, steric bulk, and electronic properties of the ligands (such as using different cyclometalating ligands and ancillary ligands), the emission color across the visible spectrum can be tuned while maintaining high color saturation. This is achieved by modifying the HOMO-LUMO energy gap through ligand selection, allowing precise control over emission wavelength.
Solution Approach 2:
The patent employs composite materials by combining multiple ligand types with the iridium metal center to create heteroleptic complexes. These composite molecular structures integrate different functional components: cyclometalating ligands for color tuning, ancillary ligands for stability and photophysical properties, and substituents for solubility and device performance. This composite approach enables simultaneous optimization of color saturation and tunability.
2Adaptability or versatility
If the OLED is designed to emit white light, then full color display can be achieved, but the color accuracy is reduced compared to saturated color emission
Solution Approach 1:
The patent applies segmentation by dividing the white light emission into separate saturated red, green, and blue emitting layers or pixels. Each segment uses iridium complexes tuned to emit at specific wavelengths, allowing individual optimization of color saturation for each primary color. This segmented approach enables full color display capability while maintaining high color accuracy, as each color can be independently optimized without compromise.
3Ease of manufacture
If organic materials are used in OLEDs, then cost advantages and flexibility are achieved, but the emission efficiency and color tuning range are limited
Solution Approach 1:
The patent replaces conventional organic fluorescent emitters with organometallic phosphorescent complexes, substituting one emission mechanism for another. The phosphorescent iridium complexes utilize triplet state emission, which is otherwise non-radiative in organic materials. This substitution dramatically increases emission efficiency by harvesting both singlet and triplet excitons, while the organic ligand framework maintains solution processability and fabrication flexibility.
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 use of this compound in OLEDs enables efficient and tunable emission, potentially leading to improved color accuracy and efficiency in full color displays.
Implementation Method 1
One application for phosphorescent emissive molecules is a full color display
Implementation Method 2
OLEDs make use of thin organic films that emit light when voltage is applied across the device
Data Source
AI summary
Compounds comprising a first ligand and a second ligand; wherein the first ligand coordinates to a first metal through a first metal-carbene bond; the second ligand coordinates to a second metal through a second metal-carbene bond; the second ligand also coordinates to the first metal; the first ligand can link to the second ligand to form a multidentate ligand; and the first metal and the second metal are each independently selected from the group consisting of Au, Ag, and Cu can act as electron acceptors in tandem to increase the energy separation between the ground and excited state, which is higher than those found in analogous monometallic complexes. These compounds should find application as luminescent materials in organic light emitting diodes (OLEDs).