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High Aspect Ratio Metallic Structures for Use as Transparent Electrodes

Ames Laboratory

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Technology Marketing SummaryIowa State University and Ames Laboratory researchers have developed metallic structures that can be used as transparent electrodes or to enhance the performance of solar cells or LEDs. Efforts to develop new energy sources and more energy efficient devices has lead to advancements such as organic solar cells (OSC) and organic light emitting devices (OLEDs). These advancements have included the development of processing techniques that offer lower cost and more simple fabrication methods, as well as the ability to employ flexible substrates in fabrication.DescriptionMost OSCs and OLEDS use indium tin oxide (ITO)-coated substrates as the anode electrode since it provides good transparency for visible light and low sheet resistance for electrical current conduction. However, the use of ITO for anode electrodes suffers from several drawbacks, including brittleness, high cost, poor mechanical stability, poor chemical compatibility with active organic materials, and high cost due to limited indium availability. As a consequence, there has been an active search for conducting electrodes with optical and electrical properties that are the same or better than ITO, and which could lead to improved device performance.

Potential replacements for ITO include carbon nanotube networks, random silver nanowire meshes, and patterned nanowire grids. Carbon nanotube networks and random silver nanowire meshes have suitable optical transparencies, but their electrical conductivities are not as good as that for ITO and they also suffer from current shunting. Patterned nanowire grids have good visible transparency, but their sheet resistance is significantly higher than that for bulk metals (although it is similar to that for ITO). To address these limitations, ISU and Ames Laboratory researchers have developed a method for fabricating high aspect ratio metallic structures that can be used as transparent electrodes for organic solar cells. Because these structures have high light transmission and superior electrical conductivity, they may also enhance solar cell performance. In addition, different metallic materials may be chosen to the address requirements of specific applications such as OSCs or OLEDs.

These structures may also have utility as infrared heat control filters due to their high reflection of infrared radiation, and are fabricated using techniques amenable to high throughput and mass production. Since the electrodes can be fabricated on flexible substrates, applications involving flexible displays and flexible solar panels may be enabled.
Benefits# High light transmission ( approximately 80% in the visible spectrum)
# Superior electrical conductivity compared to standard ITO glass (resistance is from 2.4 -7.3 Ω)
# Versatile (different materials can be employed to optimize specific applications)
# Flexible (can be fabricated on flexible substrates)
Applications and IndustriesSolar cell manufacturing; solid state lighting; optical systems.More InformationSamples of the electrodes are available for testing, and ISU is seeking partners interested in commercializing this technology.Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated

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