OLED Pixel Definition Layer Step Structure Prevents Anode Edge Breakdown
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Solution Overview
Problem
In organic light emitting displays, open edges can occur during the formation of the emission layer, leading to dielectric breakdown at the edge of the anode electrode, which compromises the reliability of the device.
Innovation Solution
The solution involves forming a pixel definition layer with a thick film portion and a step portion at both ends, where the step portion is 0.3 μm thick or less, and the anode electrode is positioned under the thick film portion, with the emission layer overlapping the step portion. The step portion has a first surface contacting the anode electrode at an angle of 45 degrees or less, preventing open edges and ensuring proper insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel definition layer is used to cover the anode electrode edge, then the structure is simple, but open edges occur during emission layer formation leading to dielectric breakdown
Solution Approach 1:
The pixel definition layer is segmented into two distinct portions: a thick film portion (first thickness) and a step portion (second thickness less than first thickness). This segmentation allows the thick film portion to provide robust insulation preventing dielectric breakdown, while the step portion enables proper emission layer formation without open edges.
Solution Approach 2:
Different portions of the pixel definition layer are given different thicknesses to fulfill different functions. The thick film portion provides enhanced insulation at critical areas, while the thinner step portion allows proper contact and prevents open edges. This local differentiation of properties resolves the contradiction between reliability and structural simplicity.
2Manufacturing precision
If the emission layer is patterned using laser induced thermal imaging, then patterning precision is improved, but open edges still occur at the anode electrode edge
Solution Approach 1:
The pixel definition layer is pre-formed with a step portion that creates an inclined surface before emission layer deposition. This preliminary structural preparation ensures that when the emission layer is deposited using laser induced thermal imaging, it can properly contact the anode electrode edge without forming open edges, even though the patterning process itself is precise.
Solution Approach 2:
The solution moves from a two-dimensional planar structure to a three-dimensional stepped structure. The step portion introduces a vertical dimension with an inclined surface, providing a gradient transition that facilitates proper emission layer contact and prevents open edges, complementing the precise lateral patterning.
Data Source
AI summary
An organic light emitting display and a manufacturing method that prevents an open edge from occurring when forming an emission layer of an organic light emitting display in order to prevent a dielectric breakdown from occurring at the edge of an anode electrode. The organic light emitting display includes: a substrate; an active layer formed on the substrate; a planarization layer formed on the active layer; an anode electrode formed on the planarization layer; a pixel definition layer formed on the upper surface of the planarization layer to cover an edge of the anode electrode; and an organic thin film formed on the pixel definition layer, wherein the pixel definition layer includes a thick film portion and a step down portion that is formed to be stepped down at both ends of the thick film portion.