Transparent solar cells could enable windows that generate electricity

The team developed a new kind of polymer solar cell that produces energy by absorbing infrared light instead of visible light, making the cells 70% transparent to the human eye. "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," said Yang Yang, professor of materials science and engineering at UCLA. The cells are made from a photoactive plastic and are lightweight and flexible. The researchers say they could be produced in high volume at low cost. Part of the breakthrough is the development of a transparent conductor made of a mixture of silver nanowire and titanium dioxide nanoparticles. According to the researchers, this composite electrode allows the transparent solar cells to be fabricated economically by solution processing and also achieves 4% power conversion efficiency. German photovoltaics manufacturer Heliatek also recently announced that its transparent solar films could be integrated within double glazing to create energy harvesting windows that look like tinted glass. The company said that the transparency level and colour could be adjusted to suit customers' requirements with the cells achieving up to 40% transparency and 7% efficiency. The firm recently signed a development agreement with Reckli to integrate the solar films onto concrete building walls.