Transparent Conductors

Transparent conducting oxides (TCOs) are ubiquitous and are found in a wide range of devices including flat panel displays, touch-sensitive screens, and solar cells. For instance, indium tin oxide (ITO) is one of the most widely used TCOs because it combines a very low resistivity (1x10^-4 ohm cm) with a high transparency of 80-90% for visible light. In most conventional devices, the TCO is used in the form of a thin film on a flat glass plate and consequently conventional thin film coating methods using line-of-sight deposition techniques are adequate. However, for advanced photovoltaics, especially those employing non-planar geometries or nanostructuring, alternative deposition techniques are required for preparing the TCO layers. Atomic layer deposition (ALD) is a synthesis technique that uses alternating, self-limiting chemical reactions to deposit materials in an atomic layer-by-layer fashion and is uniquely suited for coating porous materials. Argonne researchers are developing new techniques for preparing transparent conducting oxide thin films by ALD. In particular, they are developing new ALD chemistries capable of preparing precise, ultrathin films inside of nanoporous templates for fabricating next-generation solar cells. Another focus of their research is to scale up the ALD synthesis of transparent conducting thin films to accelerate the transition of this technology to industry. 

Concentric nanotubes of TiO2 and transparent conducting ITO provide rapid charge flow to improve the efficiency of nanostructured solar cells.

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