Fluorinated Aromatic Additives for OLED Hole Injection Layers
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Solution Overview
Problem
The performance of OLEDs with hole injection layers based on PEDOT/PSS is limited by short lifetime and low efficiency, and existing additives like NAFION are expensive, insoluble in water and organic solvents, and have low general applicability.
Innovation Solution
A composition comprising a conductive polymer, a solvent, and a low molecular weight compound with tailored solubility, specifically a fluorinated or perfluorinated aromatic group, is used to enhance the performance of OLEDs by improving the hole injection layer, which can be synthesized in a simple 1-2 step process from commercially available precursors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NAFION is used as an additive in hole injection layers, then OLED performance is improved, but the additive is expensive and has limited solubility in water and organic solvents
Solution Approach 1:
The patent changes the molecular weight parameter of the fluorinated sulfonic acid from high (polymeric NAFION) to low (molecular weights of 100-500 g/mol), which fundamentally alters solubility properties. The low molecular weight compounds are soluble in both water and organic solvents at concentrations of 0.1-10 wt%, whereas NAFION is insoluble and expensive. This parameter change resolves the contradiction between performance improvement and ease of manufacture.
2Reliability
If PEDOT/PSS is used as hole injection layer, then conductivity is achieved, but lifetime and efficiency are limited
Solution Approach 1:
The patent introduces low molecular weight fluorinated sulfonic acids as intermediary substances that mediate between the PEDOT/PSS conductive polymer and the substrate. These intermediaries improve hole injection efficiency and device lifetime by facilitating charge transport and stabilizing the interface, thereby resolving the performance limitations of pure PEDOT/PSS layers.
3Reliability
If fluorinated sulfonic acid polymers are used as additives, then OLED performance improves, but they are not soluble in water or organic solvents and merely form colloids
Solution Approach 1:
The patent segments the large polymeric NAFION molecules into smaller low molecular weight fluorinated sulfonic acid molecules. This segmentation breaks down the insoluble polymer into discrete small molecules that can be individually solvated by both water and organic solvents, achieving complete dissolution rather than colloid formation and enabling broader adaptability with conductive polymer dispersions.
Data Source
AI summary
The present invention relates to a compound having a general formula selected from the group consisting of formula Ia and Ib wherein K represents an aromatic or heteroaromatic group in which at least one hydrogen atom may be substituted by a functional groups selected from the group consisting of a sulfonic acid group, a sulfuric acid group, an ammonium group and an aliphatic group; X is selected from the group consisting of a C-C-bond, O, S, SO2 and NR', wherein R' represents a hydrogen or an aliphatic or aromatic group; A represents a fluorinated or perfluorinated aromatic group; n represents an integer in the range from 2 to 6; m represents an integer in the range from 1 to 3. The present invention also relates to a composition comprising this compound, to a process for the preparation of a conductive layer using this composition, to a conductive layer comprising the compound according to the present invention, to electronic components comprising this conductive layer and to the use of the compound according to the present invention as an additive in a hole-injection layer of an OLED or in an organic solar cell.