Series-Connected OLED Segmentation for Heat Reduction
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Solution Overview
Problem
The challenge in organic light-emitting devices (OLEDs) is the increased resistance of light-transmissive conductive electrode layers, leading to reduced luminance efficiency, element deterioration, and expanded brightness distribution due to heat generation, particularly in large-area applications.
Innovation Solution
A method for producing OLEDs with a plurality of light-emitting sections electrically connected in series on a light-transmissive substrate, involving the formation of patterned conductive electrode layers, laminated organic compound layers, and selectively removing parts of these layers using a laser beam to create dividing grooves, ensuring efficient electrical connection and reduced resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light-transmissive conductive material is used for electrodes to extract light, then light extraction is improved, but resistance increases causing heat generation and reduced luminance efficiency
Solution Approach 1:
The device is divided into multiple light-emitting units connected in series, with each unit having its own light-transmissive electrode. This segmentation allows each electrode to have smaller area and lower resistance, reducing heat generation while maintaining overall light extraction efficiency through the series connection architecture.
Solution Approach 2:
A charge generation layer is introduced as an intermediary component between the light-transmissive electrodes and the organic light-emitting layers. This layer generates charge carriers (electrons and holes) that are injected into the transport layers, enabling the light-transmissive electrodes to function with lower current density and reduced resistive heating.
2Illumination intensity
If current density is increased to achieve high brightness, then brightness is improved, but heat generation increases causing organic thin film deterioration
Solution Approach 1:
By dividing the device into multiple light-emitting units connected in series, the total operating voltage is distributed across units while maintaining lower current density in each unit. This allows achieving high overall brightness through series connection of multiple lower-brightness units, preventing organic film deterioration from excessive current density.
Solution Approach 2:
The invention changes the electrical operating parameters by switching from parallel connection (high current density) to series connection (lower current density, higher voltage). This parameter change maintains brightness while reducing the harmful current density that causes organic thin film deterioration.
3Power
If multiple light-emitting units are laminated in series to increase driving voltage, then driving voltage and brightness are improved, but light absorption by laminated body reduces luminance efficiency
Solution Approach 1:
The device is segmented into multiple light-emitting units with each unit having its own light-transmissive electrode and organic light-emitting layer. By connecting these segmented units in series rather than laminating thick layers, the invention achieves high driving voltage while minimizing light absorption losses, as each segment remains thin and transparent.
Solution Approach 2:
Instead of increasing luminance efficiency by laminating multiple layers in the vertical dimension (which increases absorption), the invention achieves high driving voltage by connecting units in series in the electrical circuit dimension. This dimensional change allows voltage increase without proportionally increasing light absorption losses.
4Area of stationary object
If device area is enlarged for illumination application, then illumination coverage is improved, but resistance of light-transmissive electrode increases causing heat generation and brightness distribution expansion
Solution Approach 1:
The large-area device is segmented into multiple smaller light-emitting units distributed across the area, each with its own light-transmissive electrode. This segmentation ensures each local electrode maintains low resistance, preventing heat generation and brightness non-uniformity even as the overall device area increases for illumination applications.
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 results in a high-performance OLED with minimized heat generation and improved brightness distribution, maintaining high luminance efficiency even in large-area devices.
Implementation Method 1
simultaneously removing a part of the laminated layer and a part of the second electrode layer by application of laser beam from a side of the substrate
Implementation Method 2
Organic EL elements constituting an organic EL device each are a semiconductor element converting electrical energy into optical energy
Implementation Method 3
at least one of these electrodes using a light-transmissive conductive material so that light generated within the element is extracted outside
Implementation Method 4
That causes heat generation in power distribution
Data Source
AI summary
The present invention aims to reduce a problem such as deterioration, a reduced luminance efficiency, and an enlarged brightness distribution due to heat generation mainly caused by a resistance value of a light-transmissive conductive electrode layer. In a device according to the present invention, a first conductive electrode layer being patterned and light transmissive is formed on a light-transmissive substrate and a laminated layer containing a plurality of organic-compound layers is formed so as to cover at least a part of the first electrode layer. The laminated layer is partly removed so that the first electrode layer is partly exposed. At least one layer containing a second conductive electrode layer is formed on the laminated layer and the exposed part of the first electrode layer. A part of the laminated layer and a part of the second electrode layer are simultaneously removed by application of laser beam from a side of the substrate, so that a plurality of light-emitting sections are electrically connected in series on the substrate.