OLED Driving Transistor Channel Doping for Grayscale Voltage Range
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Solution Overview
Problem
High-resolution organic light emitting diode (OLED) displays face challenges in adjusting the gate voltage range of driving transistors to achieve a wide range of grayscales due to reduced current per pixel, making it difficult to display various shades effectively.
Innovation Solution
The OLED display incorporates a substrate with semiconductor layers, specific gate insulating layers, and doping concentrations in channel regions of transistors to broaden the gate voltage range, including a switching semiconductor layer, a driving semiconductor layer, and light emission control semiconductor layers with varying doping concentrations and impurity types, along with a method of manufacturing that involves channel doping and gate electrode formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pixel size is reduced to increase resolution, then the display resolution is improved, but the current per pixel is reduced and the gate voltage driving range becomes narrow
Solution Approach 1:
The patent applies different doping concentrations to different transistor types within the same pixel circuit. Specifically, the driving transistor has a higher doping concentration (2×10^11 to 5×10^13 /cm³) in its channel region compared to other transistors (9×10^10 /cm³ or less). This local differentiation allows the driving transistor to maintain adequate current driving capability even when pixel size and overall current are reduced, thereby preserving the gate voltage driving range necessary for displaying multiple grayscales despite the resolution increase.
2Ease of operation
If the doping concentration of the driving transistor channel is increased, then the gate voltage driving range is broadened, but the transistor structure complexity increases
Solution Approach 1:
The patent resolves the contradiction by changing the doping concentration parameter of the driving transistor channel region to a specific range (2×10^11 to 5×10^13 /cm³). This parameter adjustment broadens the gate voltage driving range without requiring additional transistor structures or complex circuit modifications. The solution maintains the existing transistor architecture while optimizing the electrical properties through controlled doping, thus avoiding increased structural complexity.
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 configuration allows for a broader gate voltage range, enabling the display of a wide range of grayscales while improving charge mobility and maintaining threshold voltage consistency across transistors, thus enhancing the display's grayscale capabilities.
Implementation Method 1
A doping concentration of a channel region of the driving semiconductor layer may be higher than the doping concentration of the channel region of the light emission control semiconductor layer
Implementation Method 2
improving charge mobility
Data Source
AI summary
An organic light emitting diode display includes: a substrate; a semiconductor layer formed on the substrate and including a switching semiconductor layer, a driving semiconductor layer, and a light emission control semiconductor layer spaced apart from each other; a first gate insulating layer covering the semiconductor layer; a light emission control gate electrode formed on the first gate insulating layer and overlapping the light emission control semiconductor layer; a second gate insulating layer covering the light emission control gate electrode; a switching gate electrode and a driving gate electrode formed on the second gate insulating layer and respectively overlapping the switching semiconductor layer and the driving semiconductor layer; and an interlayer insulating layer covering the switching gate electrode, the driving gate electrode, and the second gate insulating layer. A doping concentration of a channel region of the driving semiconductor layer is higher than a doping concentration of a channel region of the light emission control semiconductor layer.