Light Emitting Element Insulation Layer Discontinuity Leakage Current
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Solution Overview
Problem
In organic electroluminescence display devices, leakage currents between electrodes can occur, leading to image blurring and chromaticity shifts, despite existing solutions that increase the resistance of charge injection/transport layers, which may still be insufficient in preventing such currents.
Innovation Solution
A light emitting element configuration with a first electrode, multiple insulation layers, and a charge injection/transport layer that is discontinuous at the protruding end portion of the second insulation layer, preventing leakage currents by increasing the resistance and ensuring reliable charge transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the resistance of charge injection/transport layer is increased to prevent leakage currents, then leakage current prevention is improved, but the charge transport efficiency may deteriorate
Solution Approach 1:
The charge injection/transport layer is designed with spatially varying resistance: high resistance regions are positioned near electrode edges where leakage currents occur, while low resistance regions are positioned in the center to maintain charge transport efficiency. This local differentiation resolves the contradiction by providing high resistance only where needed for leakage prevention without compromising overall charge transport.
Solution Approach 2:
The charge injection/transport layer is segmented into multiple regions with different resistance characteristics. By dividing the layer into high-resistance edge regions and low-resistance central regions, the patent simultaneously achieves leakage current prevention at edges and efficient charge transport in the center, resolving the contradiction between reliability and productivity.
2Productivity
If a continuous charge injection/transport layer is used to ensure charge transport, then charge transport efficiency is improved, but leakage currents between adjacent light emitting elements increase
Solution Approach 1:
The charge injection/transport layer exhibits local quality variations with high resistance near electrode edges and low resistance in the center. This local differentiation allows the layer to simultaneously provide efficient charge transport in the center while preventing leakage currents at the edges through high resistance, thus resolving the contradiction between productivity and harmful factors.
Solution Approach 2:
The layer is segmented into functional regions: central low-resistance zones for charge transport and peripheral high-resistance zones for leakage prevention. This segmentation enables the continuous layer to fulfill both roles, maintaining charge transport efficiency while blocking leakage currents between adjacent light emitting elements.
3Manufacturing precision
If pixel pitch is reduced for high resolution, then display resolution is improved, but the difficulty of forming three sub-pixels per pixel increases
Solution Approach 1:
The patent merges the charge injection/transport layer formation process with the color filter layer formation process. By combining these two layers into a single formation step, the device complexity is reduced, enabling high-resolution displays with fine pixel pitch while maintaining three sub-pixels per pixel without significantly increasing manufacturing complexity.
Solution Approach 2:
The charge injection/transport layer is designed to serve multiple functions: it provides charge transport for the light emitting elements and simultaneously acts as a color filter layer. This multi-functionality reduces the number of separate layers needed, simplifying the device structure and making it feasible to implement high-resolution displays with fine pixel pitch.
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 configuration effectively prevents leakage currents between electrodes, maintaining desired chromaticity and improving the light emitting performance of the display device.
Implementation Method 1
a charge injection/transport layer which is cut at the covers of the insulation layer or the resistance of which is increased and indicating at least one of a charge injection property and a charge transport property
Implementation Method 2
an organic layer including one or more light emitting layers common in all the pixels
Data Source
AI summary
A light emitting element and display device are disclosed. In one example, a light emitting element includes a first electrode formed on a base body. A first insulation layer is formed on the base body and the first electrode and has an aperture portion in which a part of the first electrode is exposed. A second insulation layer is formed on the first insulation layer and has a protruding end portion protruding from the aperture portion. A third insulation layer is formed on the second insulation layer and has an end portion recessed from the protruding end portion. A charge injection/transport layer is formed over the second insulation layer and the third insulation layer. An organic layer includes a light emitting layer, and a second electrode formed on the organic layer. At least a part of the charge injection/transport layer is discontinuous at the protruding end portion.