Heliatek GmbH, a technology company in the field of organic photovoltaics, has announced that its transparent solar films could be used to be integrated between the glass sheets of double glazed windows. These windows would look like tinted glass as the unique vapor deposition technology for the solar films allows for a homogeneous coating of the solar layer without any distracting patterns or irregularities.  

 The ultra-thin solar films by Heliatek lend themselves to integration between glass. The transparency level as well as the color can be tuned to suit the customers' requirements. Measurements by SGS, an accredited and independent testing facility, have confirmed that Heliatek's lab cells still offer an efficiency of 7 % at a light transmission level of 23.5 %. Currently, the company can produce a transparency level of up to 40 % in its laboratories in Dresden, Germany, and sees the possibility to increase this to 50 % when the transparent solar films will be supplied to the building industry with the launch of the next production line in 2014. 

Heliatek transparent solar film

 SGS had previously confirmed in another measurement campaign the superior low light and high temperature performance of Heliatek's cells compared to traditional solar technologies. At an irradiation of only 100 W/msquared the efficiency is 15 % higher compared to the standard efficiency measured at 1,000 W/msquared. The cell efficiency also remains constant with rising temperatures in contrast to traditional solar technology, which efficiency drops by 15 % to 20 % at elevated temperatures. Dr. Martin Pfeiffer, co-founder and CTO of Heliatek, said, "Our thin and lightweight solar films can be integrated directly into various kinds of building materials, so there is no need for separate mounting structures. As the film maintains its efficiency at high temperatures, unlike traditional PV technologies, no cooling is required. Similarly, its low light capabilities mean that the orientation and angle of the film is not critical and it maintains its efficiency even when cloudy, north-facing, or in the morning and evening." 

 Heliatek recently announced a joint development agreement with RECKLI to integrate its solar films onto concrete building walls. This will enable vertical concrete walls to become highly efficient solar energy harvesters without the need for supporting structures or cooling mechanisms. 

Key to Heliatek's technology is the family of small organic molecules - oligomers - developed and synthesized at its own lab in Ulm, Germany. Heliatek is the only solar company in the world that uses the deposition of small organic molecules in a low temperature, roll-to-roll vacuum process. Its solar tandem cells are made of nanometers-thin layers of high purity and uniformity. This technology is very similar to the well-established OLED technology (organic LEDs) except that it operates in reverse, taking in light to create electricity.

Heliatek is currently working with glass and other building material manufacturers to include its solar film technology in their products. "Our solar films offer unique and compelling key benefits for all kinds of building integration applications. Thus, our business model is to be the leading supplier of customized solar films to the building and construction material industry. They will integrate our solar films as energy harvesting components into their products," comments Thibaud Le Séguillon, CEO of Heliatek.