This new polymer solar cell or PSC, produces energy by absorbing infrared light and is not visible. The cells are thus nearly 70 percent transparent to the human eye. Made of photoactive plastic, the cells are seen as highly viable solutions for building integrated solar installations.
"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," says study leader Yang Yang, a UCLA professor of materials science and engineering, who also is director of the Nano Renewable Energy Center at California NanoSystems Institute (CNSI) and holder of the Carol and Lawrence E. Tannas Jr. Endowed Chair in Engineering.
The cells are lightweight and flexible being made of plastic-like materials and can be produced in high volume at low costs. Previously, many attempts have been made toward demonstrating visibly transparent or semitransparent PSCs. 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.
A team of UCLA researchers from the California NanoSystems Institute, the UCLA Henry Samueli School of Engineering and Applied Science and UCLA’s Department of Chemistry and Biochemistry have demonstrated high-performance, solution processed, visibly transpatent polymer solar cells through the incorporation of near-infrared light-sensitive polymer and silver nanowire composite films as the top transparent electrode. The photoactive polymer absorbs more near-infrared light thus balancing performance and transparency in the visible wavelength region.
Another breakthrough is the 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, four percent power-conversion efficiency for solution-processed and visibly transparent polymer solar cells has been achieved.