Buffer Composition for OLED Anode Work Function
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Solution Overview
Problem
Current organic electronic devices, such as OLEDs, face inefficiencies due to the low work function of materials like ITO, leading to less effective hole injection into electroluminescent materials, and existing surface treatments often result in unstable products with reduced device lifetime.
Innovation Solution
A buffer composition comprising semiconductive oxide particles and a fluorinated acid polymer or a semiconductive polymer doped with a fluorinated acid polymer is used to enhance the work function of the anode, improving hole injection and device stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ITO is used as the transparent anode, then the device structure is simple and easy to manufacture, but the work function is relatively low (4.6 eV) resulting in less effective hole injection into the EL material
Solution Approach 1:
The patent applies composite materials by combining ITO with a buffer layer made from semiconductive oxide particles (such as ZnO, In2O3, or SnO2) and a conducting polymer (such as PEDOT:PSS). This composite structure integrates the transparency and ease of manufacture of ITO with the high work function and improved hole injection efficiency of the buffer layer, resolving the contradiction between ease of manufacture and hole injection efficiency.
2Reliability
If surface treatment is applied to improve the work function of ITO, then the hole injection efficiency is improved, but the product stability is reduced and device lifetime is shortened
Solution Approach 1:
The patent introduces a buffer layer as an intermediary between the ITO anode and the EL material. This buffer layer acts as a mediator that provides stable, high work function properties for effective hole injection without requiring unstable surface treatments on the ITO itself. The buffer layer composition (semiconductive oxide particles combined with conducting polymer) ensures both stability and functionality, resolving the contradiction between hole injection efficiency and product stability.
3Reliability
If surface treatment is applied to improve the work function of ITO, then the hole injection efficiency is improved, but the device lifetime is reduced
Solution Approach 1:
The buffer layer serves as a protective intermediary that enables improved hole injection efficiency while preserving device lifetime. By placing the high work function material in the buffer layer rather than treating the ITO surface directly, the device achieves enhanced hole injection without the degradation and shortened lifetime associated with surface treatments, thus resolving the contradiction between hole injection efficiency and device lifetime.
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 proposed solution increases the work function of the anode, enhancing hole injection efficiency and extending the lifetime of organic electronic devices by stabilizing the buffer layer composition.
Implementation Method 1
a semiconductive polymer doped with a fluorinated acid polymer
Implementation Method 2
The anode is typically any material that has the ability to inject holes into the electroluminescent ("EL") material
Data Source
AI summary
Buffer compositions comprising semiconductive oxide particles and at least one of (a) a fluorinated acid polymer and (b) a semiconductive polymer doped with a fluorinated acid polymer are provided. Semiconductive oxide particles include metal oxides and bimetallic oxides. Acid polymers are derived from monomers or comonomers of polyolefins, polyacrylates, polymethacrylates, polyimides, polyamides, polyaramides, polyacrylamides, polystrenes. The polymer backbone, side chains, pendant groups or combinations thereof may be fluorinated or highly fluorinated. Semiconductive polymers include polymers or copolymers derived from thiophenes, pyrroles, anilines, and polycyclic heteroaromatics. Methods for preparing buffer compositions are also provided.A buffer composition consisting essentially of semiconductive oxide particles wherein the semiconductive oxide particles comprise a bimetallic oxide selected from indium-tin oxide (“ITO”), indium-zinc oxide (“IZO”), gallium-indium oxide, and zinc-antimony double oxide and a fluorinated acid polymer wherein the fluorinated acid polymer has a formula according to Formula XV:where j≧0, k≧0 and 4≦(j+k)≦199,Q1 and Q2 are F or H,Rf2 is F or a perfluoroalkyl radical having 1-10 carbon atoms either unsubstituted or substituted by one or more ether oxygen atoms,h=0 or 1, i=0 to 3, g=0 or 1,wherein the buffer composition has a work-function greater than 5.0 eV. In some embodiments, the H on the SO3 may be replaced by either Li, Na, or K.