Researchers at the University of California Los Angeles (UCLA) have developed a new transparent solar cell that could eventually be applied on windows.
The new polymer solar cell (PSC) produces energy by absorbing mainly infrared light – as opposed to visible light – making the cells nearly 70% transparent to the human eye, according to UCLA's NanoSystems Institute (CNSI). The PSCs were developed from a photoactive plastic that converts infrared light into an electrical current.
‘These results open the potential for visibly transparent polymer solar cells as add-on components of portable electronics, smart windows and building-integrated photovoltaics and in other applications,’ explains Yang Yang, a UCLA professor and director of the CNSI's Nano Renewable Energy Center." Our new PSCs are made from plastic-like materials and are lightweight and flexible. More importantly, they can be produced in high volume at low cost."
Scientists have also been studying how PSCs can be used for other applications, including building-integrated photovoltaics and integrated PV chargers.
Previously, many attempts have been made toward demonstrating visibly transparent or semitransparent PSCs, CNSI explains. However, these demonstrations often result in low visible light transparency and/or low device efficiency because suitable polymeric PV materials and efficient transparent conductors were not well deployed in device design and fabrication.
However, the CNSI researchers incorporated near-infrared, light-sensitive polymer and used silver nanowire composite films as the top transparent electrode. The near-infrared photoactive polymer absorbs more near-infrared light but is less sensitive to visible light, balancing solar cell performance and transparency in the visible wavelength region, the CNSI explains.
They also used transparent conductor made of a mixture of silver nanowire and titanium dioxide nanoparticles, which was able to replace the opaque metal electrode used in the past. This composite electrode also allows the solar cells to be fabricated economically by solution processing. With this combination, they achieved a 4% power-conversion efficiency for solution-processed and visibly transparent polymer solar cells, according to CNSI.
The study was supported by the Henry Samueli School of Engineering and Applied Science, the Office of Naval Research and The Kavli Foundation.
