July 22, 2012
Solar Cells Could Produce Energy-Generating Windows
redOrbit Staff & Wire Reports - Your Universe Online
Researchers from a prominent California university have developed a new transparent solar cell that they say could be used to create windows which generate electricity.Writing in the journal ACS Nano, UCLA Materials Science and Engineering Professor Yang Yang and colleagues describe a polymer solar cell (PSC) which is capable of producing energy by absorbing primarily infrared light, not visible light.
As such, this allows the cells, which were crafted from a type of photoactive plastic that converts infrared light into an electrical current, but be nearly 70% transparent to the human eye, the Los Angeles-based university said in a recent statement.
"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," Yang, who also serves as the director of the Nano Renewable Energy Center at California NanoSystems Institute (CNSI), said in a statement. "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."
According to UCLA, PSCs are in demand because of their advantages over other forms of solar cell technology, and scientists have been studying their potential applications in high-performance visibly transparent photovoltaic (PV) devices, including building-integrated photovoltaics, integrated PV chargers for portable electronics, and other similar instruments.
Previous attempts to create transparent or semitransparent PSCs have typically resulted in low visible light transparency, low device efficiency, or both. The reason for this, the university explained, is because suitable polymeric PV materials and efficient transparent conductors had not been well deployed in device design and fabrication.
So Yang's team attempted to tackle the issue, successfully demonstrating "high-performance, solution-processed, visibly transparent polymer solar cells through the incorporation of near-infrared light-sensitive polymer and using 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."
"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," the university added. "This composite electrode also allows the solar cells to be fabricated economically by solution processing. With this combination, 4% power-conversion efficiency for solution-processed and visibly transparent polymer solar cells has been achieved."
Along with Yang, CNSI Director Paul S.Weiss, materials science and engineering postdoctoral researcher Rui Zhu, doctoral candidates Chun-Chao Chen, Letian Dou, Choong-Heui Chung, Tze-Bin Song and Steve Hawks; Gang Li, and CNSI postdoctoral researcher Yue Bing Zheng were all credited as authors on the study, UCLA said. Their work was supported by the Henry Samueli School of Engineering and Applied Science, the Office of Naval Research, and The Kavli Foundation.