OLED Pixel Bypass Transistor for High Contrast Ratio
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Solution Overview
Problem
High-resolution organic light emitting diode (OLED) displays face challenges in maintaining a high contrast ratio due to increased black current, which results in brighter-than-intended black luminance, deteriorating image quality.
Innovation Solution
Incorporating a bypass transistor that diverts a portion of the driving current away from the organic light emitting diode during the black luminance period, using a variable voltage to control the bypass current and maintain optimal contrast ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If material efficiency of organic light emitting diode is improved and current density is increased for high resolution structure, then luminance and emission efficiency are improved, but black current increases causing brighter-than-intended black luminance which deteriorates contrast ratio
Solution Approach 1:
The pixel circuit is segmented into multiple current paths: a first current path through the organic light emitting diode for light emission, and a second current path through the bypass transistor for current diversion. This segmentation allows independent control of light-emitting current and black current, enabling high luminance while maintaining low black current for accurate black display and high contrast ratio.
Solution Approach 2:
The bypass transistor serves as an intermediary element that diverts excess current away from the organic light emitting diode during black display periods. By introducing this intermediate current path, the patent enables precise control of the current flowing through the OLED, allowing efficient light emission when needed while preventing unwanted current flow that would degrade black luminance and contrast ratio.
2Manufacturing precision
If bypass transistor is used to divert current during black luminance period, then contrast ratio is improved, but device complexity increases
Solution Approach 1:
The bypass transistor is integrated into the existing pixel circuit architecture and serves multiple functions: diverting current during black display periods to maintain contrast ratio, and being controllable through existing scan signals and emission control signals. This multi-functionality approach allows the bypass mechanism to be implemented without requiring entirely separate control circuits, thereby limiting the increase in device complexity while achieving improved contrast ratio.
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 solution effectively reduces the light emitting current during black luminance, improving the contrast ratio and maintaining accurate image representation without significantly impacting general luminance stages.
Implementation Method 1
An organic light emitting diode (OLED) display displays images by using organic light emitting diodes (OLED) that generate light by recombining electrons and holes
Data Source
AI summary
A pixel and an organic light emitting diode (OLED) display using the pixel are disclosed. The pixel includes a driving transistor for transmitting a driving current, an OLED configured to receive a first portion of the driving current and a bypass transistor configured to receive a second portion of the driving current.