Dual Pixel-Defining Layer for OLED Leakage Current
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Solution Overview
Problem
Organic light-emitting display devices face issues with leakage current generation due to direct contact between hole transporting and electron transporting layers without the light-emitting layer in between, caused by pinning points formed during the solution process.
Innovation Solution
The use of a dual pixel-defining layer structure with a lyophilic first pixel-defining layer and a lyophobic second pixel-defining layer, where the first organic layer is a hole injection layer and the second organic layer is a hole transporting layer, with distinct fluorine ion concentrations and temperatures to prevent direct contact and form isolated pinning points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single pixel-defining layer with lyophobic properties is used, then the solution composition can be properly confined during formation, but the hole transporting layer and electron transporting layer may directly contact each other at pinning points, causing leakage current
Solution Approach 1:
The pixel-defining layer is divided into two distinct layers: a first pixel-defining layer with lyophilic properties and a second pixel-defining layer with lyophobic properties. This segmentation allows the first layer to prevent direct contact between charge transporting layers (avoiding leakage current) while the second layer maintains proper solution composition confinement during formation.
Solution Approach 2:
Different regions of the pixel-defining structure are assigned different surface properties: the first pixel-defining layer has lyophilic properties to create isolated pinning points and prevent layer shorting, while the second pixel-defining layer has lyophobic properties to confine the solution composition. This local differentiation of surface properties resolves the contradiction between preventing leakage current and maintaining manufacturing precision.
2Manufacturing precision
If the pixel-defining layer is made lyophobic to confine solution composition, then manufacturing precision is improved, but the hole injection layer may form pinning points that cause direct contact between organic layers, generating leakage current
Solution Approach 1:
The pixel-defining layer is segmented into two functional layers with opposite surface properties. The first layer (lyophilic) prevents harmful pinning point formation by ensuring proper organic layer adhesion and isolation, while the second layer (lyophobic) maintains solution composition confinement, thereby eliminating the harmful effects while preserving manufacturing precision.
Solution Approach 2:
The first pixel-defining layer acts as an intermediary between the substrate and the second pixel-defining layer. It mediates the interaction between the organic layers and the pixel-defining structure, creating isolated pinning points that prevent direct contact between charge transporting layers, thus eliminating leakage current while allowing the second layer to maintain solution confinement.
3Ease of manufacture
If the organic light-emitting layer is formed by solution process, then ease of manufacture is improved, but pinning points may form causing direct contact between hole transporting and electron transporting layers
Solution Approach 1:
The first pixel-defining layer is prepared in advance with lyophilic properties before the solution process. This preliminary preparation ensures that when the organic light-emitting layer is formed by solution process, the organic material will adhere properly to the first pixel-defining layer at isolated pinning points, preventing direct contact between charge transporting layers and maintaining layer separation integrity throughout the ease-of-manufacture solution process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively prevents or reduces leakage current, improving the efficiency and lifetime of the organic light-emitting element by maintaining the integrity of the light-emitting layer and ensuring proper layer separation.
Implementation Method 1
the first pixel-defining layer shows lyophilic properties
Implementation Method 2
a concentration of fluorine ions bonded onto the surface of the first pixel-defining layer may differ from a concentration of fluorine ions bonded onto the surface of the second pixel-defining layer
Implementation Method 3
The second pixel-defining layer may show lyophobic properties
Implementation Method 4
When the excitons transition from an excited state to a ground state, the emissive layer may emit light
Data Source
AI summary
An organic light-emitting display device is provided. An organic light-emitting display device, including: a substrate; a pixel-defining layer on the substrate and defining a light-emitting region; and an organic light-emitting element over the light-emitting region, wherein the pixel-defining layer includes a first pixel-defining layer on the substrate and a second pixel-defining layer on the first pixel-defining layer, the organic light-emitting element includes a first organic layer contacting the first pixel-defining layer at either end thereof, a second organic layer on the first organic layer and contacting the second pixel-defining layer at either end thereof, and an organic light-emitting layer on the second organic layer, and the first pixel-defining layer is lyophilic.