OLED Pixel Electrode Formation via Halftone Mask PDL
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing manufacturing processes for organic light-emitting display apparatuses face challenges such as increased costs due to multiple patterning processes, potential damage to lower electrodes during pixel electrode patterning, and changes in TFT characteristics from harmful gases generated in subsequent processes.
Innovation Solution
The proposed solution involves a structure where the pixel electrode is directly formed on the source and drain electrodes of the TFT without a planarization or passivation layer, using a pixel-defining layer with varying thickness areas and a via hole to connect the pixel electrode to the TFT, and an intermediate layer with an emission layer, while omitting unnecessary patterning steps to reduce manufacturing costs and protect the TFT from external harm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple patterning processes are used to form the pixel electrode, then the pixel electrode can be precisely formed, but the manufacturing cost increases and the lower electrode may be damaged
Solution Approach 1:
The pixel-defining layer is divided into multiple thickness regions (first area with first thickness, second area with second thickness greater than the first, and optional third area with intermediate thickness) to create different functional zones. This segmentation allows the pixel electrode to be formed with precise thickness control in different areas through a single patterning process using a halftone mask, eliminating the need for multiple patterning steps while preventing damage to the lower electrode.
Solution Approach 2:
The solution transitions from controlling pixel electrode thickness through multiple planar patterning steps to controlling it through the vertical dimension by creating a pixel-defining layer with varying thickness. The halftone mask enables formation of different thickness areas (first, second, and optional third areas) in a single process, adding a vertical thickness dimension to the patterning approach and simplifying the manufacturing process.
2Manufacturing precision
If subsequent patterning processes are performed after TFT formation, then the pixel electrode can be formed, but harmful gases may change TFT characteristics
Solution Approach 1:
The pixel-defining layer is formed with varying thickness areas and via holes before the pixel electrode patterning process. This preliminary structure preparation allows the pixel electrode to be formed directly in the first area without requiring subsequent patterning processes that would generate harmful gases. The via holes are pre-formed to enable direct electrical connection, eliminating the need for additional etching or patterning steps that could expose the TFT to harmful gases.
Solution Approach 2:
The pixel-defining layer acts as an intermediary structure between the TFT and the pixel electrode. It provides a pre-formed template with varying thickness areas and via holes that guides the pixel electrode formation process, eliminating the need for direct patterning of the pixel electrode that would require harmful subsequent processes. This intermediary layer protects the TFT from exposure to harmful gases while enabling precise pixel electrode formation.
3Reliability
If a planarization or passivation layer is added to protect the TFT, then the TFT is protected from damage, but the device complexity and manufacturing cost increase
Solution Approach 1:
The pixel-defining layer serves multiple functions simultaneously: it defines the pixel area, provides thickness variation for precise pixel electrode formation, creates via holes for electrical connection, and protects the underlying TFT structure. By combining these multiple functions into a single layer formed in one patterning process using a halftone mask, the invention eliminates the need for separate planarization or passivation layers, reducing device complexity while maintaining TFT protection.
Data Source
AI summary
An organic light-emitting display apparatus includes a substrate; a thin film transistor (TFT) on the substrate; a pixel-defining layer (PDL) disposed on the TFT and comprising a first area having a first thickness and a second area having a second thickness greater than the first thickness, and a via hole in the first area; a pixel electrode disposed on at least a portion of the first area, and electrically connected to the TFT via the via hole; an intermediate layer on the pixel electrode, the intermediate layer comprising an emission layer (EML); and an opposite electrode on the intermediate layer. According to a method of manufacturing the organic light emitting display apparatus, the PDL is formed on the substrate and then the pixel electrode is formed on the first area.