1. A new architecture for transparent electrodes: relieving the trade-off between electrical conductivity and optical transmittance
- Author
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Rakesh C. Mahadevapuram, Tae Geun Kim, Wai Leung, Kristen P. Constant, Ping Kuang, Joong Mok Park, Kai-Ming Ho, Sumit Chaudhary, and Kanwar S. Nalwa
- Subjects
Materials science ,Organic solar cell ,Optical Phenomena ,Polymers ,Surface Properties ,Nanotechnology ,Carbon nanotube ,law.invention ,law ,Transmittance ,General Materials Science ,Electrical conductor ,Electrodes ,Sheet resistance ,business.industry ,Mechanical Engineering ,Electric Conductivity ,Tin Compounds ,Indium tin oxide ,Mechanics of Materials ,Metals ,Electrode ,Optoelectronics ,business ,Light-emitting diode - Abstract
Transparent conducting electrodes with the combination of high optical transmission and good electrical conductivity are essential and desirable in solar energy harvesting and electric lighting devices including organic solar cells and light-emitting diodes (LEDs) as well as in their inorganic counterparts. Currently, indium tin oxide (ITO) coated glass is most often used because ITO has relatively high transparency to visible light and low sheet resistance for electrical current conduction. However, ITO is costly due to limited resources, is brittle, [ 1 ] and has poor chemical compatibility with the active organic materials. [ 2 ] These disadvantages have motivated the search for other conducting electrodes with similar or better optical and electrical properties. In recent research efforts, carbon nanotube networks, unpatterned thin metal fi lms, random silver metal nanowire meshes, graphene fi lms, and patterned metal nanowire grids have been evaluated as potential replacements for ITO electrodes. [ 3โ11 ] Although these alternative transparent electrode approaches do have the potential to replace ITO, they still suffer from the classic trade-off between the optical transmittance and electrical conductivity. Thicker layers offer higher conductivity, but this comes at the expense of optical transmittance, and vice versa. Here, we report a new architecture for transparent electrodes, which leads to quasi-elimination of this tradeoff. This architecture consists of high-aspect-ratio metallic ribbons with nanoscale thickness and microscale width, spaced at desired periodicities and held in place by a polymer matrix to provide a fl at top surface for fabrication of active layers in solar cells or LEDs. By design, the light path is only obstructed by the nanoscale thickness of the ribbons, thus decoupling the conductivity and transmittance properties from each other. Catrysse and Fan performed theoretical investigations on similar nanopatterned metallic structures, and their simulations indicate that such structures have excellent optical and electrical properties for potential use as transparent conductive electrodes. [ 12 ] Our experimental results show that the novel structure is very promising for such applications.
- Published
- 2011