Ultraviolet Cleaning of Metal Oxide Hole Injection Layers
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Solution Overview
Problem
The manufacturing of organic EL elements faces challenges due to adsorbates from carbon dioxide, water, and organic materials in the atmosphere, which embed between layers and increase drive voltage and reduce longevity, especially when using metal oxide hole injection layers.
Innovation Solution
A method involving the formation of a hole injection layer with metal oxide, followed by ultraviolet light irradiation with wavelengths greater than those that decompose oxygen molecules, to remove adsorbates without affecting the energy level from oxygen vacancies, allowing for efficient hole injection and low voltage operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ultraviolet light irradiation is used to remove adsorbates from the hole injection layer surface, then manufacturing precision and element longevity are improved, but device complexity increases due to additional processing steps
Solution Approach 1:
The ultraviolet light irradiation is performed as a preliminary cleaning step immediately after forming the hole injection layer and before forming the functional layers. This preliminary action removes adsorbates from the surface, preventing their embedding in subsequent layers and ensuring high manufacturing precision without requiring complex in-situ cleaning systems.
Solution Approach 2:
The patent replaces complex mechanical or chemical cleaning systems with a simple ultraviolet light irradiation process. This substitution achieves effective surface cleaning while significantly reducing device complexity, as ultraviolet irradiation requires only a light source rather than complex vacuum or chemical processing equipment.
2Manufacturing precision
If conventional cleaning methods are used to remove adsorbates, then surface cleanliness is improved, but the energy level from oxygen vacancies is affected and hole injection efficiency deteriorates
Solution Approach 1:
The patent changes the parameter of cleaning method from conventional mechanical or chemical cleaning to ultraviolet light irradiation. This parameter change allows effective removal of adsorbates while preserving the oxygen vacancy structures on the metal oxide surface, thereby maintaining the energy levels necessary for efficient hole injection.
Solution Approach 2:
The patent converts the potential harm of surface adsorbates into a benefit by using ultraviolet light to selectively remove them. The ultraviolet irradiation targets only the adsorbates without affecting the oxygen vacancies, thus converting the harmful adsorbate layer into a clean surface that maintains both cleanliness and hole injection efficiency.
3Device complexity
If adsorbates are not removed from the hole injection layer surface, then device complexity is reduced, but drive voltage increases and element longevity decreases
Solution Approach 1:
The ultraviolet light irradiation is performed as a preliminary cleaning step immediately after forming the hole injection layer and before forming the functional layers. This preliminary action removes adsorbates from the surface, preventing their embedding in subsequent layers and ensuring high manufacturing precision without requiring complex in-situ cleaning systems.
Solution Approach 2:
The patent replaces complex mechanical or chemical cleaning systems with a simple ultraviolet light irradiation process. This substitution achieves effective surface cleaning while significantly reducing device complexity, as ultraviolet irradiation requires only a light source rather than complex vacuum or chemical processing equipment.
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
This method enables the production of organic EL elements that operate at low voltage with high intensity and longevity by maintaining the energy level from oxygen vacancies, preventing adsorbate embedding and carrier trap formation.
Implementation Method 1
irradiating the hole injection layer with ultraviolet light, the ultraviolet light having a wavelength greater than a wavelength at which oxygen molecules decompose and yield oxygen radicals
Data Source
AI summary
A method of manufacturing an organic EL element operating at low voltage to emit light at high intensity comprises: a first step of forming, on an anode, a hole injection layer including metal oxide; a second step of irradiating the hole injection layer with ultraviolet light, the ultraviolet light having a wavelength greater than a wavelength at which oxygen molecules decompose and yield oxygen radicals; a third step of forming functional layers containing organic material on or above the hole injection layer after the second step, the functional layers including a light-emitting layer; and a fourth step of forming a cathode on or above the functional layers.