OLED Sub-Pixel Leakage Current Detection Method
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Solution Overview
Problem
Existing OLED manufacturing processes face challenges in detecting and addressing parasitic sub-pixel leakage current, which can lead to nonconformal color coordinates and increased costs due to defective products.
Innovation Solution
A method is developed to estimate parasitic sub-pixel leakage current by measuring currents at specific luminance levels and calculating a weighted average current leakage, allowing for preliminary screening and diversion of OLED arrays to monochromatic displays if leakage is excessive, thereby reducing waste and processing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current leakage in OLED sub-pixels is not detected during manufacturing, then production cost increases due to defective products, but implementing detection adds complexity to the manufacturing process
Solution Approach 1:
The patent implements preliminary detection of current leakage in OLED sub-pixels during the manufacturing process, specifically after organic stack deposition and before seal layer deposition. This early detection allows identification of defective pixels before further processing, preventing waste of subsequent manufacturing steps and enabling timely diversion to monochromatic display production.
Solution Approach 2:
The patent employs a self-diagnostic approach where the OLED device under manufacturing is used to detect its own defects. By applying voltages to individual sub-pixels and measuring current leakage through the device's own structure, the system performs self-testing without requiring external specialized equipment, thereby simplifying the manufacturing process while maintaining detection capability.
2Manufacturing precision
If OLED arrays with leakage current are processed as color displays, then color coordinate conformity deteriorates, but diverting them to monochromatic displays increases production complexity
Solution Approach 1:
The patent implements a feedback mechanism where current leakage measurements taken during manufacturing provide information about pixel quality. Based on this feedback, the system determines whether to proceed with color display processing or divert to monochromatic display production. This closed-loop approach ensures that only suitable pixels are processed as color displays, maintaining color coordinate conformity while optimizing production efficiency.
Solution Approach 2:
The patent changes the operational parameter of the OLED display from color to monochromatic mode for pixels exhibiting excessive current leakage. By detecting leakage current levels and adjusting the display mode accordingly, the system maintains optimal performance for each pixel type, ensuring color accuracy for suitable pixels while utilizing otherwise defective pixels for monochromatic applications.
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 effective quality control, reducing the likelihood of color coordinate shifts and associated costs by identifying and processing arrays with high leakage current as monochrome, ensuring efficient production and maintaining substrate integrity.
Implementation Method 1
An electric current is applied to the device, causing negatively charged electrons to move into the organic material(s) from the cathode. Positive charges, typically referred to as holes, move in from the anode. The positive and negative charges meet in the center layers (i.e., the semiconducting organic material), combine, and produce photons.
Data Source
AI summary
A method is provided for performing quality control on an organic light emitting diode (OLED) pixel comprising three sub-pixels formed in parallel. A method is provided for determining an weighted average current leakage for three sub-pixels of an OLED pixel. The method includes selecting a total luminance level, determining a first current flowing when a first sub-pixel is energized causing the OLED pixel to emit light having 1/3 total luminance. The method includes determining a second current flowing when the first sub-pixel and a second sub-pixel are energized causing the OLED pixel to emit light having a 213 total luminance. The method includes calculating weighted average current leakage by multiplying the first current times two forming a first product, subtracting the second current from the first product forming a result, multiplying the result by two forming a second product, and dividing the second product by nine. A computer-readable medium is provided.