Phosphorescent Iridium Complex for High-Efficiency Light Emission
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional light-emitting elements using fluorescent compounds have a theoretical internal quantum efficiency limit of 25% due to the statistical generation ratio of singlet to triplet excited states, whereas phosphorescent compounds can achieve up to 75-100% efficiency by converting triplet excited energy into luminescence, but effective phosphorescent materials with high phosphorescence quantum yield are needed to realize this potential.
Innovation Solution
A light-emitting device incorporating a phosphorescent organometallic iridium complex where nitrogen at specific positions of pyrimidine or 1,3,5-triazine is coordinated to iridium, with an ortho-metalated aryl group structure, enhancing the conversion of triplet excited energy into phosphorescence, and is used in conjunction with other organic compounds to form an exciplex or charge-generation layers for improved efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fluorescent compounds are used in light-emitting elements, then the device structure is simple and ease of manufacture is improved, but the internal quantum efficiency is limited to 25% due to statistical generation ratio of singlet to triplet excited states
Solution Approach 1:
The patent changes the fundamental parameter of the light-emitting compound from fluorescent to phosphorescent type, specifically using iridium complex compounds that exhibit phosphorescence. This parameter change enables utilization of triplet excited states for light emission, thereby improving internal quantum efficiency from the theoretical 25% limit of fluorescent compounds to potentially 100% efficiency by converting both singlet and triplet excited states into luminescence.
2Use of energy by moving object
If phosphorescent compounds are used to achieve high internal quantum efficiency of 75-100%, then emission efficiency is improved, but the requirement for effective phosphorescent materials with high phosphorescence quantum yield increases device complexity
Solution Approach 1:
The patent employs composite material design by creating organometallic iridium complex compounds that integrate organic ligands (such as pyridine, pyrimidine, triazine derivatives) with the iridium metal center. This composite structure combines the advantages of organic compounds (tunability, processability) with the phosphorescence properties of metal complexes, achieving high phosphorescence quantum yield while maintaining relative ease of manufacture through established coordination chemistry methods.
3Ease of manufacture
If conventional fluorescent compounds are used, then manufacturing process is simple, but power consumption is high due to limited energy utilization from triplet excited states
Solution Approach 1:
The patent converts the previously harmful or wasted triplet excited states (which do not emit light in fluorescent compounds and represent lost energy) into beneficial light-emitting states through phosphorescence. By using iridium complex compounds with phosphorescent properties, the triplet excited states that would otherwise be lost are now converted into luminescence, reducing energy loss and lowering power consumption while maintaining manufacturing simplicity.
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 these phosphorescent organometallic iridium complexes in light-emitting elements significantly enhances emission efficiency, allowing for higher luminance with reduced power consumption and extended device lifetime by effectively utilizing triplet excited states, thereby overcoming the efficiency limitations of fluorescent-based devices.
Implementation Method 1
phosphorescence refers to luminescence generated by transition between different energies in multiplicity. In an ordinary organic compound, phosphorescence refers to luminescence generated in returning from the triplet excited state to the singlet ground state
Implementation Method 2
A compound that can easily cause intersystem crossing from the singlet excited state to the triplet excited state (or a compound that allows the forbidden transition of photoexcitation directly to the triplet excited state) is thus required as such a photosensitizer
Implementation Method 3
Organic compounds are brought into an excited state by the absorption of light. Through this excited state, various reactions (photochemical reactions) are caused in some cases, or luminescence is generated in some cases
Implementation Method 4
The light-emitting element including an organic compound as a light-emitting substance has a light emission mechanism that is of a carrier injection type: voltage is applied between electrodes where a light-emitting layer is interposed, electrons and holes injected from the electrodes are recombined to make the light-emitting substance excited, and then light is emitted in returning from the excited state to the ground state
Data Source
AI summary
A new light-emitting device utilizing phosphorescence is provided. Further, an electronic device and a lighting device which utilize phosphorescence are provided. One embodiment of the present invention is a light-emitting device including a phosphorescent organometallic iridium complex comprising iridium and either pyrimidine having an aryl group at the 4-position or 1,3,5-triazine having an aryl group at the 2-position. One of nitrogen in the pyrimidine or 1,3,5-triazine is coordinated to the iridium. Also, each of the pyrimidine and 1,3,5-triazine has a substituent such as an alkyl group or an aryl group. Further the ortho position of the aryl group which is bonded to the 4-position of the pyrimidine or the 2-position of the 1,3,5-triazine is bonded to the iridium.