OLED Display Peripheral Doping for Leakage Reduction
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Solution Overview
Problem
High-resolution organic light emitting diode (OLED) displays face challenges in grayscale control and charge mobility due to the narrow driving range of gate voltage for transistors, leading to reduced charging ability and increased leakage current.
Innovation Solution
The OLED display design includes a substrate with a pixel portion and a peripheral portion, featuring semiconductor layers with specific doping regions and gate insulating layers, where the peripheral switching semiconductor layer has a larger length and doping degree than the pixel and driving semiconductor layers, and a storage capacitor with bent portions to enhance charge mobility and reduce leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the resolution of the OLED display is increased, then the display quality is improved, but the current per pixel decreases leading to reduced charging ability and narrow gate voltage driving range
Solution Approach 1:
The patent applies local quality by differentiating the doping concentration in different regions of the semiconductor layer. The pixel portion uses a first doping concentration while the peripheral portion uses a second doping concentration that is higher than the first. This localized differentiation allows the peripheral switching transistor to have sufficient charging ability even when the overall pixel current is reduced due to high resolution requirements.
2Manufacturing precision
If the resolution of the OLED display is increased, then the display quality is improved, but the gate voltage driving range becomes narrow making it difficult to control grayscales
Solution Approach 1:
The patent implements local quality by creating distinct doping concentration zones: the pixel portion semiconductor layer has a first doping concentration optimized for grayscale control, while the peripheral portion has a second doping concentration for sufficient charging. This allows the driving transistor in the pixel portion to maintain an adequate gate voltage driving range for grayscale control even in high-resolution displays where pixel currents are low.
3Reliability
If the doping concentration is increased to improve charging ability, then the charge mobility is improved, but the leakage current increases
Solution Approach 1:
The patent resolves this contradiction by applying different doping concentrations to different functional regions. The peripheral portion uses a higher second doping concentration to ensure sufficient charging ability for the switching transistor, while the pixel portion uses a lower first doping concentration to minimize leakage current and maintain grayscale control. This spatial differentiation of doping quality allows each region to optimize for its specific function.
Data Source
AI summary
An organic light emitting diode display device includes a substrate including a pixel portion and a peripheral portion, a semiconductor layer including a pixel switching semiconductor layer and a driving semiconductor layer formed on the pixel portion, and a peripheral switching semiconductor layer formed on the peripheral portion. A first gate insulating layer is formed on the semiconductor layer. A peripheral switching gate electrode is formed on the first gate insulating layer of the peripheral portion, and a pixel switching gate electrode and a driving gate electrode are formed on the first gate insulating layer of the pixel portion. A length of a peripheral switching low concentration doping region formed in the peripheral switching semiconductor layer may be larger than a length of a pixel switching low concentration doping region and a driving low concentration doping region formed in the pixel switching semiconductor layer and the driving semiconductor layer, respectively.