OLED Electrode Recess Structure for Light Efficiency
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Solution Overview
Problem
Organic light emitting display (OLED) devices suffer from low light efficiency and pixel uniformity issues due to light reflection between electrodes and non-uniform formation of the organic light emitting layer and electrodes on bank structures with inclined sidewalls or protrusions, which do not effectively redirect light back into the luminescent region.
Innovation Solution
Incorporating a reflection structure, such as a recess or protrusion structure, on the electrodes to redirect light from the non-luminescent region back into the luminescent region, with specific angle and thickness ratios to enhance light efficiency and pixel uniformity, and using a pixel defining layer with rounded sidewalls to ensure uniform formation of the organic light emitting structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a bank with inclined sidewall or protruding bank is disposed between adjacent pixels to increase effective area of organic light emitting layer, then the effective area is increased, but the light efficiency is not sufficiently increased and uniformities of pixels are deteriorated due to non-uniform formation of organic light emitting layer and electrode
Solution Approach 1:
Instead of using protruding banks that cause non-uniform formation, the patent inverts the approach by using recess structures in the electrode. This allows the organic light emitting layer to be formed uniformly on a flat surface while the recesses are created subsequently in the electrode layer to provide light reflection functionality.
Solution Approach 2:
The electrode is segmented into multiple layers (first electrode layer and second electrode layer) with the recess structure formed in the second electrode layer. This segmentation allows independent optimization of each layer's function - the first layer provides electrical connection while the second layer with recesses provides light reflection.
2Area of stationary object
If a bank with inclined sidewall or protruding bank is disposed to increase effective area, then the effective area is increased, but light reflection toward luminescent region is insufficient
Solution Approach 1:
The patent converts the harmful effect of light escaping to non-luminescent regions into a beneficial effect by providing recess structures with reflective sidewalls that redirect this escaped light back into the luminescent region, thereby recovering energy that would otherwise be lost.
Solution Approach 2:
The patent optimizes specific parameters of the recess structure including depth, width, and sidewall angle to maximize light reflection efficiency. The sidewall angle is specifically designed to redirect light at optimal angles back toward the luminescent region while maintaining uniform formation of the organic light emitting layer.
3Ease of manufacture
If conventional electrode structure is used, then manufacturing is simple, but light efficiency is poor with only about 17% of generated light being utilized
Solution Approach 1:
The recess structure is formed in the second electrode layer before the organic light emitting layer is deposited. This preliminary formation of the reflective structure ensures that subsequent layers are deposited on a controlled surface, maintaining manufacturing simplicity while enabling enhanced light reflection functionality.
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 solution increases light efficiency by more than 50% and enhances pixel uniformity, leading to improved image brightness and quality in OLED devices.
Implementation Method 1
The reflection structure of the first electrode may be configured to reflect at least part of a light generated from the organic light emitting structure and headed to the nonluminescent region toward the luminescent region
Data Source
AI summary
An organic light emitting display device may include a substrate having a switching device, a first electrode including a reflection structure and being electrically connected to the switching device, a pixel defining layer disposed on the first electrode to define a luminescent region and a nonluminescent region, an organic light emitting structure disposed over the pixel defining layer, and a second electrode disposed over the organic light emitting structure. The first electrode may include the reflection structure such as a recess structure or a protrusion structure, so that the organic light emitting display device may ensure an enhanced light efficiency. Additionally, pixels of the organic light emitting display device may have improved uniformity because an opening of the pixel defining layer may have a rounded shape.