OLED Substrate TFT Lateral Arrangement Aperture Ratio
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Solution Overview
Problem
The bottom-emission type organic light emitting display apparatus has limitations in aperture ratio due to the placement of thin film transistors (TFTs) and capacitors on the light emission path, which restricts the emission area and leads to color shift at side-surface viewing angles.
Innovation Solution
A substrate with a thin film transistor (TFT) configuration that includes a gate electrode, source electrode, and drain electrode, with specific insulating layers and electrode structures that allow direct connection between the drain electrode and the first electrode without a via hole in the third insulating layer, extending the emission area and increasing the aperture ratio, while minimizing color shift through the use of transparent conductive oxide and reflective electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If TFTs and capacitors are arranged in one pixel of bottom-emission type OLED, then the display function is achieved, but the aperture ratio is limited due to device placement on the light emission path
Solution Approach 1:
The invention changes the vertical stacking arrangement to a lateral planar arrangement. The TFT and capacitor are positioned side-by-side in the plane rather than stacked vertically on the light emission path. This dimensional change allows both devices to coexist without blocking light, thereby increasing the aperture ratio while maintaining full display functionality.
Solution Approach 2:
The pixel structure is segmented into distinct functional zones: a TFT region and a capacitor region. The TFT includes source/drain electrodes and active layer in one area, while the capacitor with its first and second electrodes occupies a separate adjacent area. This segmentation allows independent optimization of each device's light interaction characteristics, with the capacitor's transparent electrodes minimizing light blockage.
2Area of stationary object
If via holes are formed in the third insulating layer to connect drain electrode and first electrode, then electrical connection is achieved, but the emission area is reduced and color shift occurs at side-surface viewing angles
Solution Approach 1:
The invention extracts and eliminates the via hole structure from the third insulating layer. Instead of forming connection holes through the insulating layer, the drain electrode and first electrode are positioned to be directly adjacent and connected in the same plane. This removal of via holes eliminates the associated manufacturing complexity and prevents light blockage that would reduce emission area and cause color shift.
Solution Approach 2:
Instead of connecting electrodes vertically through via holes (conventional approach), the invention inverts the connection approach by placing electrodes horizontally adjacent to each other in the same plane. The drain electrode of the TFT directly contacts the first electrode of the capacitor laterally, reversing the typical vertical stacking connection method and thereby eliminating via hole requirements.
3Illumination intensity
If transparent conductive oxide is used for the first electrode, then light transmission is improved, but manufacturing complexity increases due to multiple material layer requirements
Solution Approach 1:
The first electrode of the capacitor serves multiple functions: it acts as an electrical connection element and simultaneously as a transparent conductive layer for light transmission. By using transparent conductive oxide material for this electrode, the structure achieves both electrical functionality and optical transparency without requiring separate dedicated transparent layers, thereby maintaining manufacturing simplicity while improving light transmission.
Solution Approach 2:
The invention changes the material parameter of the first electrode from conventional opaque conductive materials to transparent conductive oxide materials. This parameter change enables light transmission through the electrode while maintaining electrical conductivity, improving the overall light transmission characteristics of the display without fundamentally altering the manufacturing process flow.
Data Source
AI summary
A substrate includes a thin film transistor (TFT) which includes an active layer, a gate electrode, a source electrode, and a drain electrode; a first insulating layer disposed between the active layer and the gate electrode; a second insulating layer disposed between the gate electrode and the source and drain electrodes; a third insulating layer disposed on the second insulating layer, and including a first region for opening the second insulating layer and a second region for opening one of the source and drain electrodes, the first region and the second region being integrally connected; and a first electrode connected to one of the source and drain electrodes, and disposed so as to cover the first region and the second region.