Copper OLED Emitter Material for Deep Red TADF Emission
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Solution Overview
Problem
Existing OLEDs face challenges in achieving efficient electroluminescence in the deep red color range and require high energy input due to the use of expensive elements like iridium or platinum, while circularly polarized light emission is not efficiently utilized for anti-reflective filters.
Innovation Solution
The use of a paracyclophane-carbene compound as a ligand in a metal complex, particularly copper(I) complexes, enables efficient thermally activated delayed fluorescence (TADF) for deep red electroluminescence and circularly polarized luminescence, allowing high light yield with low energy input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If phosphorescent triplet emitters with expensive metal complexes (iridium or platinum) are used, then efficient conversion of excitons to light is achieved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive phosphorescent metal complexes (iridium or platinum) with cheaper copper-based emitters that utilize TADF mechanism. The copper complexes, while less expensive, achieve comparable or superior efficiency through thermally activated delayed fluorescence, making the emitter material more cost-effective while maintaining high exciton conversion efficiency.
Solution Approach 2:
The patent changes the emission mechanism from phosphorescent triplet (using heavy metals) to thermally activated delayed fluorescence (using copper complexes). This parameter change in the emission mechanism allows the use of cheaper metals while maintaining efficient exciton conversion, as the TADF process can achieve high quantum efficiencies without requiring expensive phosphorescent materials.
2Object-affected harmful factors
If linear polarisers combined with quarter-wave plates are used as filters, then reflection of other light sources is reduced, but light loss increases (only 50% of light passes through)
Solution Approach 1:
The patent employs circularly polarized light emission from the copper-based emitter materials to interact with anti-reflective filters. The circular polarization characteristic of the emitted light allows 100% transmission through the filters, eliminating the 50% light loss associated with linear polarizers and quarter-wave plates, while still providing effective reflection reduction.
Solution Approach 2:
The patent uses chiral copper complexes that emit circularly polarized light, combining the emitter material with anti-reflective filter characteristics. This composite approach allows the emission source itself to possess the polarization properties needed for efficient filter transmission, eliminating the need for separate linear polarizer and quarter-wave plate components that cause light loss.
3Illumination intensity
If conventional emitter materials are used, then green-emitting OLEDs perform well, but efficient electroluminescence in the deep red color range is not achieved
Solution Approach 1:
The patent modifies the emitter material parameters by using copper complexes with specific ligands (such as N-heterocyclic carbene ligands) that enable deep red emission. The copper-based TADF emitters with appropriate ligand field strengths can achieve efficient electroluminescence in the deep red range, overcoming the limitation of conventional materials that perform well only in the green range.
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
This solution provides high light yield and low-energy operation with moderate costs, particularly in the red spectral range, and enhances image quality by utilizing circularly polarized light for improved contrast through anti-reflective filters.
Implementation Method 1
An alternative is luminescence via thermally activated delayed fluorescence (TADF), which can be realised with complexes of the much cheaper element copper or cheap organic compounds
Implementation Method 2
the circularly polarised light (circularly polarised luminescence, CPL) generated by chiral emitter materials with a high dissymmetry factor glum can pass through the filters 100%
Data Source
AI summary
The present disclosure relates to emitter materials for OLEDs based on defined metal complexes and their corresponding application in OLEDs.