Organic Light-Emitting Display Device Upper Light-Shielding Layer
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Solution Overview
Problem
Organic light-emitting display devices experience non-uniform image display due to threshold voltage variation in thin film transistors caused by external light exposure, leading to differences in sub-pixel luminance.
Innovation Solution
An upper light-shielding layer is disposed over the pixel driving circuit to absorb or reflect external and internal light, preventing light from reaching the active layer and thus stabilizing the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If no upper light-shielding layer is provided, then the device structure is simpler, but threshold voltage variation occurs due to light exposure causing non-uniform image display
Solution Approach 1:
An upper light-shielding layer is introduced as an intermediary component between the light-emitting element and the pixel driving circuit. This layer mediates the light interaction by absorbing or reflecting light before it reaches the active layer of the transistor, thereby preventing threshold voltage variation while maintaining a relatively simple overall device structure.
Solution Approach 2:
The light-shielding function is segmented into two distinct layers: a lower light-shielding layer positioned beneath the active layer and an upper light-shielding layer positioned above the pixel driving circuit. This segmentation allows each layer to specifically address light exposure from different directions, with the upper layer specifically targeting threshold voltage stability by blocking light from reaching the transistor gates.
2Reliability
If the upper light-shielding layer covers a large area, then light blocking effectiveness is improved, but the active area for light emission is reduced
Solution Approach 1:
The upper light-shielding layer is designed with spatially varying properties: it is positioned specifically over the pixel driving circuit area where transistors are located, rather than uniformly across the entire device. This localized approach ensures that light blocking is applied only where needed (over the transistor gates) while leaving the light-emitting areas of the display untouched, thus maintaining image uniformity without sacrificing emission area.
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
The solution effectively reduces light input to the active layer, preventing threshold voltage variation and improving image uniformity by blocking light from the sides and upper surface, thereby enhancing the display's consistency.
Implementation Method 1
The upper light-shielding layer absorbs or reflects light input from outside or light generated from the light-emitting element
Implementation Method 2
The upper light-shielding layer absorbs or reflects light input from outside or light generated from the light-emitting element
Data Source
AI summary
The present disclosure relates to an organic light-emitting display device capable of preventing threshold voltage variation in a thin film transistor. In the organic light-emitting display device according to the present disclosure, an upper light-shielding layer overlying a pixel driving circuit which drives a light-emitting element is disposed on the same plane as an anode electrode and a bank is disposed to cover the sides of the upper light-shielding layer, and thus light input to the sides and the upper surface of an active layer can be blocked.