OLED Self-Buffer Layer Solvent Protection
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Solution Overview
Problem
Conventional polymer OLED manufacturing methods using spin coating result in defects due to solvents dissolving lower layers, leading to reduced lifespan and color purity, as solvents with high solubility compromise the formation of desired layer thicknesses.
Innovation Solution
Incorporating a self-buffer layer made of conductive polymer between the hole transport and light emitting layers, and between the light emitting and electron transport layers, using solvents with lower solubility to protect the underlying layers and ensure adequate thickness, thereby reducing defects and improving layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a solvent with high solubility is used for spin coating to form the light emitting layer, then the layer can be formed to desired thickness, but the underlying hole transport layer and hole injection layer are dissolved causing defects
Solution Approach 1:
The patent introduces a buffer layer made of conductive polymer as an intermediary between the hole transport layer and the light emitting layer. This buffer layer acts as a protective mediator that prevents the high-solubility solvent used for forming the light emitting layer from dissolving the underlying hole transport layer, thus resolving the contradiction between achieving desired layer thickness and preventing layer dissolution defects
Solution Approach 2:
The buffer layer is formed in advance before depositing the light emitting layer. This preliminary action creates a protective barrier that prevents subsequent solvent damage to the hole transport layer, allowing the use of high-solubility solvents for optimal light emitting layer formation without compromising underlying layers
2Reliability
If a solvent with low solubility is used for spin coating to protect underlying layers, then layer defects are reduced, but the light emitting layer cannot be formed to desired thickness
Solution Approach 1:
The conductive polymer buffer layer serves as a protective intermediary that enables the use of high-solubility solvents for forming the light emitting layer to desired thickness without damaging underlying layers. The buffer layer absorbs the harmful effect of the solvent, allowing optimal thickness formation while maintaining reliability
3Reliability
If multiple functional layers are added to improve OLED performance, then lifespan and efficiency are improved, but the complexity of the multi-layer thin film structure increases making manufacturing more difficult
Solution Approach 1:
The buffer layer made of conductive polymer serves multiple functions: it protects underlying layers from solvent dissolution, facilitates charge transport, and enables proper interface formation between layers. This multi-functionality reduces the need for additional separate protective layers, thereby managing complexity while maintaining reliability improvements
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 self-buffer layer enhances the lifespan and color purity of OLEDs by protecting the underlying layers and allowing for proper thickness formation, increasing the light emitting lifetime and improving color purity compared to OLEDs without this structure.
Implementation Method 1
a solution used for the spin coating method can dissolve the hole injection layer and a hole transport layer, which are lower layers, since the solution contains a solvent such as chlorobenzene, toluene, xylene, cyclohexanone, chloroform, or THF, which has high solubility with a main component of the light emitting layer
Implementation Method 2
polymer OLEDs are mainly manufactured by a spin coating method or an ink jet method, i.e., wet processes, to form multi-layer thin films
Implementation Method 3
OLEDs are devices that transform electrical energy into optical energy in an organic material. That is, the OLEDs are devices that emit light by generating excitons by recombining holes and electrons respectively injected from an anode and a cathode into the organic material
Data Source
AI summary
An organic light emitting device (OLED) and a method of manufacturing the OLED. The OLED includes an anode, a cathode, a hole transport layer arranged between the anode and the cathode, a self-buffer layer arranged between the hole transport layer and the cathode, the self-buffer layer being adapted to protect the hole transport layer, the self-buffer layer being made of a first material and a light emitting layer arranged between the self-buffer layer and the cathode, the light emitting layer also being made of the first material.