OLED Blue Subpixel HOD Structure for Longer Lifespan
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Solution Overview
Problem
Organic light emitting display devices face limitations in peak luminance due to the blue subpixel's relatively low efficiency and short lifespan, necessitating larger blue subpixels to enhance blue characteristics.
Innovation Solution
The implementation of a blue subpixel with a hole only device (HOD) structure, where two blue emission material layers are symmetrically stacked with respect to a charge generation layer and driven by two driving transistors, allowing for alternating light emission based on voltage polarities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the blue subpixel size is increased to enhance blue characteristics, then blue emission efficiency and lifespan are improved, but the overall display device complexity and area utilization are worsened
Solution Approach 1:
The blue subpixel is segmented into two separate emission material layers (first blue emission material layer and second blue emission material layer) that can be independently driven by different driving transistors. This segmentation allows each layer to be activated alternately, effectively doubling the lifespan of the blue subpixel while maintaining the same physical area, thus resolving the contradiction between reliability and device complexity.
Solution Approach 2:
The blue subpixel employs a dynamic driving mechanism where two driving transistors alternately activate the two emission material layers based on voltage polarity. This dynamic operation enables the blue subpixel to maintain high efficiency and extended lifespan without requiring a larger physical area, thereby resolving the contradiction between reliability and device complexity.
2Illumination intensity
If the blue subpixel size is increased to improve blue characteristics, then blue emission efficiency is enhanced, but the peak luminance of the unit pixel is limited
Solution Approach 1:
By segmenting the blue emission into two separate layers that can be activated alternately, the system achieves high blue emission efficiency without requiring a larger subpixel area. This maintains the overall peak luminance of the unit pixel while enhancing blue characteristics through the segmented structure.
Solution Approach 2:
The two blue emission material layers are activated in periodic alternation through the driving transistors responding to voltage polarity changes. This periodic action ensures that blue emission efficiency is enhanced while the overall peak luminance remains balanced across all subpixels, resolving the contradiction between blue emission efficiency and peak luminance.
3Device complexity
If a conventional OLED structure is used for the blue subpixel, then the structure is simple, but the lifespan and efficiency are relatively short and low
Solution Approach 1:
The blue subpixel is divided into two emission material layers with separate driving transistors, creating a dual-structure system. This segmentation doubles the effective lifespan by alternating activation between the two layers, while the overall structural complexity remains manageable through systematic design.
Solution Approach 2:
The invention changes the operational parameters of the blue subpixel by introducing voltage polarity control that selectively activates different emission material layers. This parameter change enables extended lifespan and improved efficiency while maintaining a structure that is sufficiently simple for manufacturing.
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 approach enhances blue emission characteristics while maintaining subpixels of the same size, effectively doubling the lifespan of the blue subpixel and improving overall display performance.
Implementation Method 1
an organic light emitting display device uses an organic light emitting diode (OLED), which is a self-luminous element configured to emit light from a light emission material layer thereof through re-combination of an electron and a hole
Data Source
AI summary
Discussed is an organic light emitting display device capable of achieving an enhancement in blue characteristics while having subpixels having a same size by designing a blue one of the subpixels using a hole only device (HOD) structure. The blue subpixel can include two blue emission material layers stacked to form the HOD structure. The blue subpixel can driven using two data lines and two driving transistors so that the two blue emission material layers alternately emit light on a frame basis.