Thinned Charge Generation Layer for OLED Leakage Current Suppression
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Solution Overview
Problem
The charge generation layer in tandem-type organic electroluminescence (EL) displays is highly conductive, leading to leakage currents that degrade the display quality of light emitting devices.
Innovation Solution
A light emitting device configuration where the charge generation layer is thinned in trenches between the lower electrodes and the contact portion of the upper electrode, reducing leakage currents and enhancing display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a charge generation layer is arranged between light emitting layers to increase light emitting efficiency, then the efficiency of the light emitting device can be increased, but the display quality may lower due to leakage current via the charge generation layer
Solution Approach 1:
The charge generation layer is designed with spatially varying thickness: thinner in the light emitting region (over lower electrodes) to reduce leakage current and improve display quality, while thicker in the non-light emitting region (over insulating layer) to maintain sufficient charge generation capability. This local differentiation resolves the contradiction between efficiency and display quality.
Solution Approach 2:
The charge generation layer is segmented into functionally distinct regions: a first region over the insulating layer with greater thickness for charge generation, and a second region over the lower electrodes with smaller thickness for reduced leakage. This segmentation allows each region to optimize its function independently.
2Reliability
If the charge generation layer is made thinner to reduce leakage current, then display quality improves, but charge generation capability may be reduced
Solution Approach 1:
The solution moves from a single-plane thickness constraint to a multi-dimensional spatial distribution. By varying thickness in the vertical dimension across different horizontal positions (over insulating layer vs. over lower electrodes), the design achieves both reduced leakage in light emitting regions and sufficient charge generation in non-light emitting regions.
Solution Approach 2:
Different thickness values are assigned to different spatial locations of the charge generation layer. The region over the insulating layer has greater thickness for charge generation, while the region over lower electrodes has smaller thickness for leakage reduction, allowing local optimization of competing requirements.
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
The thinning of the charge generation layer in trenches effectively suppresses leakage currents, thereby improving the light emission efficiency and maintaining high display quality in light emitting devices.
Implementation Method 1
the charge generation layer is highly conductive, the display quality of an image may lower due to a leakage current via the charge generation layer
Implementation Method 2
a light emitting device using a self-light emitting element such as an organic electroluminescence (EL) element
Data Source
AI summary
A light emitting device is provided. The device includes an insulating layer arranged on a main surface of a substrate, lower electrodes arranged on the insulating layer, an organic layer arranged to cover the lower electrodes, an upper electrode arranged to cover the organic layer, and a supply electrode configured to supply a potential to the upper electrode. The organic layer includes function layers each including a light emitting layer, and a charge generation layer arranged between the function layers, the upper electrode includes a contact portion that is in contact with the supply electrode, the insulating layer includes a trench between the contact portion and each of the lower electrodes, and a thickness of the charge generation layer in the trench is thinner than the thickness of the charge generation layer on the lower electrodes.