OLED Insulating Layer Thickness for Parasitic Capacitance
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Solution Overview
Problem
Organic light-emitting displays suffer from parasitic capacitance between wiring and the opposite electrode, which degrades image quality.
Innovation Solution
The organic light-emitting display features a substrate with a thin film transistor, wiring, and an insulating layer with distinct thickness regions, where the second region is thicker and includes a protrusion to reduce parasitic capacitance, and a pixel-defining layer that covers the edge of the pixel electrode, preventing short circuits and image quality reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wiring is provided to each pixel and an opposite electrode is formed integrally over multiple pixels, then the display structure is established and electrical connection is achieved, but parasitic capacitance occurs between the wiring and opposite electrode which reduces image quality
Solution Approach 1:
The insulating layer is designed with non-uniform thickness, featuring a first thickness in the first region and a second thickness greater than the first thickness in the second region. This local variation in insulating layer thickness creates different electrical isolation characteristics in different areas, effectively reducing parasitic capacitance between the wiring and opposite electrode while maintaining the integral structure of the opposite electrode.
Solution Approach 2:
The solution addresses the parasitic capacitance problem by introducing a vertical dimension variation through the non-uniform insulating layer thickness, rather than changing the horizontal layout of wiring or opposite electrode. This dimensional approach allows electrical isolation improvement without altering the fundamental planar structure.
2Object-affected harmful factors
If the insulating layer thickness is increased to reduce parasitic capacitance, then electrical isolation between wiring and opposite electrode is improved, but the overall device thickness and manufacturing complexity increase
Solution Approach 1:
Rather than uniformly increasing the insulating layer thickness across the entire device, the invention applies increased thickness (second thickness) only in the second region where parasitic capacitance is problematic, while maintaining a thinner first thickness in the first region. This localized approach reduces parasitic capacitance without proportionally increasing overall device complexity.
Data Source
AI summary
An organic light-emitting display that includes a substrate comprising a pixel area, a thin film transistor arranged within the pixel area, a wiring electrically connected to the a thin film transistor, an insulating layer covering the thin film transistor and the wiring, a pixel electrode arranged over the insulating layer, a pixel-defining layer having an opening that exposes the pixel electrode, an opposite electrode facing the pixel electrode and an organic emission layer interposed between the pixel electrode and the opposite electrode, the insulating layer having a first region that is overlapped by the pixel electrode and a second region that is not overlapped by the pixel electrode, the second region being thicker than the first region to reduce parasitic capacitance between the opposite electrode and the wiring.