OTFT Drain Electrode as Pixel Anode for OLED
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Solution Overview
Problem
The manufacturing process of conventional organic electroluminescent display devices is complex due to the need for multiple masking processes to form gate electrodes, source and drain electrodes, viaholes, and pixel isolation layers, which complicates the formation of a rear emission structure.
Innovation Solution
A thin film transistor (TFT) with a drain electrode acting as a pixel electrode, where one source electrode and one drain electrode are formed of different materials, with the drain electrode extending into the emission region to simplify the manufacturing process and eliminate the need for additional masking steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple masking processes are used to form gate electrode, source and drain electrodes, viaholes, and pixel isolation layer, then the device structure is complete and functional, but the manufacturing process becomes complex and time-consuming
Solution Approach 1:
The patent merges the drain electrode and pixel electrode into a single integrated structure. The drain electrode is extended to overlap the emission region, eliminating the need for separate pixel electrode formation processes. This consolidation reduces the number of masking steps and simplifies the manufacturing process while maintaining complete device functionality.
Solution Approach 2:
The drain electrode serves dual functions: it acts as the drain electrode for the thin film transistor and simultaneously functions as the pixel electrode for the organic electroluminescent layer. This multi-functionality reduces the total number of electrodes and manufacturing steps required, directly addressing the complexity issue while ensuring structural completeness.
2Manufacturing precision
If multiple masking processes are used to form various electrodes and isolation layers, then proper device regions are defined, but production time and manufacturing steps increase
Solution Approach 1:
By combining the drain electrode and pixel electrode into one continuous structure, the patent reduces multiple sequential masking operations into fewer steps. The extended drain electrode automatically defines the emission region boundary, maintaining precise region definition while significantly improving production efficiency by reducing process time.
3Ease of manufacture
If separate pixel electrode is formed through additional masking process, then electrode functions are clearly separated, but manufacturing complexity and process time increase
Solution Approach 1:
The drain electrode is designed to perform multiple functions simultaneously: electrical conduction as a drain electrode and light emission interface as a pixel electrode. This universal design simplifies manufacturing by eliminating separate pixel electrode formation while the clear functional separation is maintained through the extended overlap structure into the emission region.
Data Source
AI summary
An organic thin film transistor (OTFT) and an organic electroluminescent display (OLED) device are disclosed. The OTFT includes a drain electrode, functioning as a pixel electrode (anode electrode) of an organic emission element, such that the manufacturing process of an OLED device is simplified. In one embodiment, the OLED device includes: i) a substrate comprising an emission region and a non-emission region, ii) an organic thin film transistor, which comprises, a gate electrode, source and drain electrodes respectively overlapping both side portions of the gate electrode, and a semiconductor layer, and is disposed in the non-emission region, and iii) an organic light emitting element comprising a lower electrode, an organic layer, and an upper electrode. In one embodiment, one of the source electrode and drain electrode of the OTFT extends to the emission region, the semiconductor layer has an opening exposing a portion of the extending electrode, and the exposed portion of the extending electrode acts as a lower electrode (pixel or anode electrode) of the organic light emitting element.