Newly Developed Transparent Plastic is Also Conductive

Researchers at the University of Michigan have made plastic conductive while also being more transparent.

In their open-source recipe, the researchers sandwiched a conductive metal layer between two "dielectric" materials that allow light to pass through easily. The dielectrics reduce the reflection from both the plastic and metal layer between them.

The researchers hope that their new plastic recipe will improve large touchscreens, LED light panels, and other electronic screen devices.

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"We developed a way to make coatings with high transparency and conductivity, low haze, excellent flexibility, easy fabrication and great compatibility with different surfaces," Jay Guo, U-M professor of electrical engineering and computer science, who led the work, said in a press release. 

The dielectrics chosen by the team for their conducting plastic are aluminum oxide and zinc oxide. On the side closest to the light source, the aluminum oxide reflects less light back to the source than a plastic surface would.

Then comes the metal layer, only 6.5 nanometers thick, which is composed of silver with a tiny amount of copper in it. Zinc oxide in the metal layer helps guide the light into the plastic surface.

Though some light still gets reflected back where the plastic meets the air on the opposite side, the overall light transmission is better than plastic alone — the transmittance is 88.4%, up from 88.1% for plastic alone.

"It was taken for granted that the transmittance of the conductor is lower than that of the substrate, but we show that this is not the case," said Chengang Ji, first author of the study in Nature Communications, who worked on the project as a Ph.D. student in electrical and computer engineering. Ji received his doctorate from U-M in 2019.

Guo and his team are pushing their technology forward by collaborating on a project that uses transparent conductors in solar cells for mounting on windows. The team hopes these could absorb infrared light and convert it into electricity while letting the visible spectrum pass through and brighten the room.

Guo has also proposed large panel interactive displays and car windshields that can melt ice the way rear windows can. The work is part of a concerted effort to find new ways to use surfaces for sustainable and efficient technologies.