OLED Luminescent Layer with Tertiary Alkyl Iridium Complex
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Solution Overview
Problem
Organic electroluminescence elements (OLEDs) prepared by the coating process have a short service life due to high charge injection barriers from electrodes, which is not effectively reduced by existing copolymers, leading to increased electrical load on the luminescent layer.
Innovation Solution
Incorporating a phosphorescent compound with a specific structure, such as an iridium complex with tertiary or quaternary α-carbon atom-containing alkyl groups, into the luminescent layer, combined with a charge-transporting non-conjugated polymer, to reduce the charge injection barrier and enhance service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a coating process is used to prepare organic EL elements, then production cost is reduced and large area elements can be produced easily, but service life becomes extremely short due to high charge injection barriers
Solution Approach 1:
The patent changes the chemical structure parameters of the phosphorescent complex by introducing alkyl groups with tertiary or quaternary α-carbon atoms at specific positions (R1, R2, R3, R4, R5, R6) of the ligand molecules. This structural modification alters the electronic properties and charge injection characteristics of the complex, enabling it to function effectively in coating-prepared elements and resolve the service life issue while maintaining manufacturing advantages
Solution Approach 2:
The patent creates a composite luminescent layer by combining the specifically structured phosphorescent iridium complex with organic charge injection layers. This composite structure integrates the advantages of both materials: the phosphorescent complex provides high luminescence efficiency while the organic charge injection layers reduce the charge injection barrier, thereby extending service life without sacrificing the ease of manufacture provided by the coating process
2Reliability
If existing copolymers are used in the luminescent layer, then some improvement in service life is achieved, but the charge injection barrier from electrodes is not basically reduced
Solution Approach 1:
The patent modifies the molecular structure parameters of the phosphorescent complex by introducing alkyl groups with tertiary or quaternary α-carbon atoms at specific positions of the ligand. This structural change fundamentally alters the charge injection properties, reducing the charge injection barrier from electrodes more effectively than existing copolymer modifications alone
Solution Approach 2:
The patent introduces organic charge injection layers as intermediary materials between the electrodes and the luminescent layer containing the phosphorescent complex. These intermediary layers serve as a bridge that facilitates charge injection, reducing the harmful charge injection barrier while working synergistically with the modified phosphorescent complex to extend service life
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 solution results in OLEDs with low charge injection barriers, high luminescence efficiency, and extended service life, overcoming the limitations of existing technologies.
Implementation Method 1
the luminescent layer contains a phosphorescent compound represented by formula (1) and a charge-transporting non-conjugated polymer
Implementation Method 2
a charge-transporting non-conjugated polymer
Data Source
Figure 1
AI summary
The organic electroluminescence element includes a substrate, a pair of electrodes formed on the substrate, and one or plural organic layers between the pair of the electrodes, said organic layer containing a luminescent layer, wherein the luminescent layer contains a compound represented by the following formula (1) and a charge-transporting non-conjugated polymer; in the formula (1), R1 to R8 each are independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms; a plurality of the alkyl groups may be linked with one another to form a ring; at least two of R1 to R8 are each the alkyl group; and at least one of the alkyl groups is an alkyl group having a tertiary or quaternary a-carbon atom. The organic electroluminescence element has high luminescence efficiency and long service life.