OLED Common Hole Transport Layer Crosstalk Reduction
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Solution Overview
Problem
Active OLED displays face significant electrical crosstalk issues due to shared redox p-doped hole transport layers, which increase conductivity and lead to performance degradation.
Innovation Solution
A common hole transport layer with reduced electrical conductivity, formed by a hole transport matrix material doped with a p-dopant, is used across multiple OLED pixels, along with separate driving circuits for each pixel to control the driving current, thereby minimizing crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a common redox p-doped hole transport layer is used across multiple OLED pixels to improve conductivity and charge injection, then electrical conductivity is improved, but electrical crosstalk between pixels increases
Solution Approach 1:
The patent divides the hole transport layer into separate, electrically isolated segments for each pixel rather than using a continuous common layer. This segmentation prevents electrical crosstalk between pixels while maintaining adequate conductivity within each pixel's dedicated hole transport layer region.
Solution Approach 2:
The patent applies different electrical conductivity characteristics to different regions of the hole transport layer. Each pixel's hole transport layer has optimized local conductivity properties tailored to its specific electrical isolation requirements, rather than using uniform conductivity across all pixels.
2Ease of operation
If redox p-doping is applied to increase charge carrier concentration and improve charge injection, then charge injection is improved, but pixel crosstalk increases
Solution Approach 1:
The patent segments the doped hole transport layer into electrically isolated regions for each pixel. This allows redox p-doping to be applied locally to each pixel's hole transport layer, improving charge injection at each pixel interface while preventing dopant-mediated electrical coupling between adjacent pixels.
Solution Approach 2:
The patent introduces electrically isolating structures (such as insulating barriers or trenches) between adjacent pixel regions. These intermediary elements prevent the spread of electrical charge and dopant effects between pixels, thereby eliminating crosstalk while preserving the beneficial charge injection enhancement from redox p-doping within each pixel.
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 effectively reduces electrical crosstalk between pixels while maintaining operational stability and performance comparable to high-conductivity OLEDs, with the added benefit of suppressing pixel crosstalk.
Implementation Method 1
The use of redox p-dopants which increase charge carrier density by creation of new charge carriers (holes) by transfer of an electron from a molecule of the doped matrix to a dopant molecule
Implementation Method 2
light is produced and emitted by the light-emitting diode through the injection of charge carriers (electrons from one side, holes from the other) from the contacts into adjacent organic layers as a result of an externally applied voltage, subsequent formation of excitons (electron-hole pairs) in an active zone, and radiative recombination of these excitons
Data Source
Figure 1
AI summary
An active OLED display, comprising a plurality of OLED pixels, each of the OLED pixels comprising an anode, a cathode, and a stack of organic layers, wherein the stack of organic layers is provided between and in contact with the cathode and the anode and comprises an electron transport layer, a hole transport layer, and a light emitting layer provided between the hole transport layer and the electron transport layer, and a driving circuit configured to separately driving the pixels of the plurality of OLED pixels, wherein, for the plurality of OLED pixels, a common hole transport layer is formed by the hole transport layers provided in the stack of organic layers of the plurality of OLED pixels, the common hole transport layer comprising a hole transport matrix material and at least one electrical p-dopant, and the electrical conductivity of the hole transport material being lower than 1x10-3 S.m-1 and higher than 1x10-8 S.m-1.