Organic EL Buffer Layer Suppresses Electron Trapping
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Solution Overview
Problem
Conventional organic EL elements suffer from reduced light emission properties due to contamination and electron trapping in the light emitting layer, leading to lower brightness and uneven emission.
Innovation Solution
Incorporating a buffer layer with electron-donating properties, such as alkali metal or organic matter, between the recombination layer and the electrodes to suppress electron trapping, with a thickness of 0.1 nm to 1 nm to prevent contamination-induced function reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If multiple layers are sequentially formed by passing through multiple deposition chambers, then the organic EL element can be manufactured with standard process, but contamination may be present in the light emitting layer leading to reduced light emission properties
Solution Approach 1:
The patent introduces a buffer layer as an intermediary between the hole transport layer and the light emitting layer. This buffer layer serves as a protective mediator that prevents contamination from the deposition chamber from directly affecting the light emitting layer, thereby maintaining light emission properties while allowing standard sequential deposition processes to be used.
Solution Approach 2:
The buffer layer is formed in advance before the light emitting layer deposition. By performing this preliminary action of creating a protective buffer layer first, the light emitting layer is pre-protected from potential contamination during subsequent deposition processes, preventing electron trapping issues before they occur.
2Productivity
If materials are exposed to heat for long time in deposition chambers, then deposition can be completed, but materials may deteriorate and mix in the light emitting layer as contamination
Solution Approach 1:
The buffer layer acts as a protective intermediary that isolates the light emitting layer from deteriorated materials. Even when materials undergo heat exposure during deposition, the buffer layer prevents any deteriorated substances from contaminating the light emitting layer, maintaining material purity while allowing complete deposition processes.
Data Source
AI summary
In an organic EL element including a positive electrode, a negative electrode, and a light emitting layer (recombination layer) provided between the positive electrode and the negative electrode, an electron transport layer and an electron injection layer are provided between the light emitting layer and the negative electrode, and are sequentially arranged in the direction from the light emitting layer to the negative electrode. A hole injection layer and a hole transport layer are provided between the light emitting layer and the positive electrode, and are sequentially arranged in the direction from the positive electrode to the light emitting layer. A buffer layer for suppressing the electron trapping properties is provided between the light emitting layer and the hole transport layer.