AR-coated Ultrathin Film Offers Efficiency, Flexibility

Transparent conductors are found in many devices such as displays, light emitting diodes, photovoltaic cells, and smart phones. Most of this current technology is based on the use of the semiconductor Indium Tin Oxide (ITO) as a transparent conducting material. However, ITO is expensive to produce, lacks flexibility and must be processed under high temperatures.

A flexible transparent conductor is shown. Courtesy of ICFO.

Much research has been devoted to finding an alternative process and alternative materials to replace ITO. Researchers at the Institute of Photonic Sciences (ICFO) and its Catalan Institute of Research and Advanced Studies (ICREA) think they may have found the answer in ultrathin metal films (UTMFs) coated in layers of antireflection (AR) undercoat and overcoat.

Valerio Pruneri, ICREA professor at ICFO, said they have developed a room temperature processed multilayer transparent conductor optimizing the antireflection properties to obtain high optical transmissions and low losses, with large mechanical flexibility properties.

“We have used a simple design to achieve a transparent conductor with the highest performance to date and at the same time it has other outstanding attributes required for relevant applications in industry,” said Pruneri.

The researchers applied an Al-doped ZnO overcoat and a TiO₂ undercoat layer with precise thicknesses to a highly conductive Ag ultrathin film. By using destructive interference, the researchers showed that the proposed multilayer structure could lead to an optical loss of approximately 1.6 percent and an optical transmission greater than 98 percent in the visible.

The results of this study show the potential that this multilayer structure could have in future technologies that aim at more efficient and flexible electronic and optoelectronic devices.

The results have been published in Nature Communications (doi:10.1038/ncomms13771).