OLED Reflective Electrode Structure for Brightness and Processability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In display devices with organic light-emitting diodes (OLEDs), achieving high resolution while maintaining light-emission efficiency is challenging due to difficulties in processing reflective electrodes containing silver and forming electrical contacts between aluminum and transparent electrodes like indium tin oxide (ITO), which can lead to reduced reflectivity and increased light absorption.
Innovation Solution
The use of a conductive layer with a contact area over its entire circumference, a reflective layer of Al-Ni, Al-W, Al-Mo, or Al-Ti alloys, and a transparent electrode of indium tin oxide (ITO) is employed, where the reflective layer is completely covered by the transparent electrode to prevent corrosion and enhance electrical contact, optimizing the work function for hole injection and reducing surface unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflective electrode containing silver (Ag) is used to increase reflectivity, then light reflection efficiency is improved, but processing difficulty increases due to inability to process by dry etching
Solution Approach 1:
The patent replaces the expensive and difficult-to-process silver (Ag) reflective electrode with aluminum (Al), which is cheaper and can be easily processed by dry etching. The aluminum electrode achieves sufficient reflectivity for the application while being compatible with standard semiconductor manufacturing processes, effectively substituting a premium material with a more practical alternative.
Solution Approach 2:
The patent changes the material parameter of the reflective electrode from silver to aluminum, and adjusts the thickness parameter to 50-100 nm to optimize both reflectivity and processability. This parameter change enables dry etching processing while maintaining adequate optical performance for the display device.
2Ease of manufacture
If aluminum (Al) is used as the reflective electrode to enable dry etching processing, then manufacturing ease is improved, but electrical contact difficulty increases with transparent electrodes like ITO
Solution Approach 1:
The patent segments the electrode structure into three distinct layers: aluminum (Al) for reflectivity and processability, titanium (Ti) for electrical contact and adhesion, and indium tin oxide (ITO) for transparency and additional electrical contact. This segmentation allows each layer to specialize in its optimal function, resolving the conflict between manufacturing ease and electrical contact reliability.
Solution Approach 2:
The patent introduces titanium (Ti) as an intermediary layer between aluminum (Al) and indium tin oxide (ITO). This intermediate layer facilitates electrical contact between the two materials that have poor direct contact, while also providing good adhesion to both layers. The Ti layer acts as a mediator that enables reliable electrical connectivity without compromising the manufacturing advantages of aluminum.
3Reliability
If a conducting electrode is placed between aluminum (Al) and transparent electrode to improve electrical contact, then electrical contact reliability is improved, but reflectivity decreases due to light absorption
Solution Approach 1:
The patent applies local quality by making the titanium (Ti) layer extremely thin (5-10 nm) specifically at the interface where electrical contact is needed, while keeping the aluminum (Al) layer thicker (50-100 nm) to maintain overall reflectivity. The thin Ti layer provides sufficient electrical conductivity and adhesion locally, while minimizing its impact on the optical reflectivity of the overall electrode structure.
Solution Approach 2:
The patent carefully controls the thickness parameter of the titanium intermediate layer to be 5-10 nm, which is thin enough to minimize light absorption and maintain reflectivity, yet thick enough to provide reliable electrical contact and adhesion. This precise parameter control resolves the trade-off between electrical contact reliability and optical reflectivity.
4Ease of manufacture
If aluminum (Al) is used as reflective electrode, then manufacturing ease is improved, but corrosion resistance worsens leading to reduced device life
Solution Approach 1:
The patent creates a composite electrode structure combining aluminum (Al), titanium (Ti), and indium tin oxide (ITO). The aluminum provides reflectivity and processability, the titanium provides adhesion and corrosion resistance, and the ITO provides transparency and additional corrosion protection. This composite structure maintains the manufacturing advantages of aluminum while significantly improving corrosion resistance and device longevity through the protective Ti and ITO layers.
Solution Approach 2:
The patent applies beforehand cushioning by incorporating titanium (Ti) and indium tin oxide (ITO) protective layers over the aluminum (Al) electrode before the device is put into service. These layers act as protective barriers that prevent corrosion of the aluminum from the outset, extending device life without affecting the manufacturing processability that aluminum provides.
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 configuration improves brightness by approximately 30% compared to traditional designs, reduces drive voltage, and extends the life of the display element by preventing galvanic corrosion, thus enhancing display quality and resolution.
Implementation Method 1
a reflective layer disposed above the conductive layer on an inner side of the contact area, which reflects light
Data Source
AI summary
According to one embodiment, a display device includes a base, a first insulating layer disposed on the base, a lower electrode disposed on the first insulating layer, an organic layer disposed on the lower electrode and including a light-emitting layer and an upper electrode disposed on the organic layer, and the lower electrode includes a conductive layer including a contact area disposed over an entire circumference thereof when viewed in plan view, a reflective layer disposed above the conductive layer on an inner side of the contact area, which reflects light and a transparent electrode located on the conductive layer and the reflective layer and in contact with the contact area.