OLED Pixel Circuit with Segmented Diodes for Dark Spot Compensation
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Solution Overview
Problem
Organic light emitting displays face challenges in maintaining display quality due to defects such as dark spots in organic light emitting diodes, which can occur due to short circuits between anode and cathode electrodes, leading to reduced luminance and image stability.
Innovation Solution
The proposed solution involves a pixel structure with multiple organic light emitting diodes, where transistors are controlled by different voltage levels for emission control, allowing normal diodes to operate while defective diodes are decoupled from the pixel circuit, ensuring stable operation and high luminance even with defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single organic light emitting diode is used in a pixel, then the pixel circuit is simple, but display quality deteriorates due to dark spots and reduced luminance stability
Solution Approach 1:
The pixel is divided into multiple organic light emitting diodes (at least two) instead of using a single diode. This segmentation allows the pixel to maintain functionality even when one diode develops a dark spot defect, as the other diodes can continue to emit light and compensate for the defective one, thereby improving display quality and luminance stability.
2Reliability
If multiple organic light emitting diodes are used in a pixel, then display quality improves, but the pixel circuit complexity increases
Solution Approach 1:
Multiple organic light emitting diodes are electrically connected in parallel within the pixel structure, sharing common anode and cathode electrodes. This merging approach allows the diodes to work together to provide stable luminance while reducing the need for separate control circuits for each diode, thus improving display quality without excessively increasing circuit complexity.
Solution Approach 2:
The pixel circuit is designed to control multiple organic light emitting diodes simultaneously using a single data signal and control signal. The circuit components (transistors, capacitors) serve multiple functions by managing the electrical characteristics of all diodes in the pixel, thereby achieving reliable display quality while keeping the circuit relatively simple.
3Device complexity
If defective diodes remain connected in the pixel circuit, then the circuit structure is simple, but luminance stability decreases due to dark spots
Solution Approach 1:
The pixel circuit incorporates dynamic control mechanisms that can adjust the electrical characteristics of individual diodes based on their operational status. When a dark spot defect is detected in one diode, the circuit can dynamically redistribute current to healthy diodes, maintaining stable luminance output without requiring complex real-time monitoring systems.
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 enables stable image display and high luminance levels, with normal diodes maintaining 100% luminance and defective diodes contributing up to 90% or more, effectively improving display quality by automatically decoupling defective diodes from the pixel circuit.
Implementation Method 1
the organic light emitting display is able to display images using organic light emitting diodes that emit light by the recombination of electrons and holes
Data Source
AI summary
A pixel includes a plurality of organic light emitting diodes, each of which including a cathode electrode coupled to a second power source, a pixel circuit coupled to a scan line and to a data line, the pixel circuit configured to control current supplied from a first power source to the organic light emitting diodes corresponding to a data signal supplied to the data line, and first transistors between the pixel circuit and respective ones of the organic light emitting diodes, the first transistors configured to be turned on or to be turned off when a low emission control signal is supplied to a first emission control line, wherein a scan signal supplied to the scan line is a first voltage, and wherein the low emission control signal is a second voltage that is different than the first voltage.