Organic photovoltaic (OPV) technology is the latest generation of technology for producing solar power. The advantages over conventional solar cells are the flexibility, low weight, and low cost. This allows many options for integrating these solar cells into buildings. For example, they can be attached as a film to panes of glass, corrugated roofing, and awnings in order to capture solar energy. The energy generating industry also has a huge interest in this technology for low-cost and robust fields of solar panels.
The aim of the collaborative EU-funded SUNFLOWER project is to develop advanced flexible plastic solar cells which are favorable in cost, energy-efficient, and have long service life. The challenge is to combine these features: The efficiency of the solar cells must be 8-10%, the expected service life must be at least 20 years, and the production costs must be reduced to less than 0.70 euro/Wp* (in 2008 the production costs were still 100 euro/Wp according to the OE-A roadmap). Special attention in the development work will be put on the environmental impact and CO2 balance.
The European project will be coordinated by the Schweizer Zentrum für Elektronik und Mikrotechnik (CSEM). The project consortium comprises 17 partners from industry and R&D organizations.
In order to protect the individual layers in the organic solar cells from oxygen and water vapor, the cells must be encapsulated in barrier films. These barrier films consist of a plastic substrate film that is coated with several alternating layers of inorganic materials and hybrid polymers. In order to achieve a service life of at least 20 years, the films must have water vapor transmission of less than 5x10-4 gm-2d-1 and oxygen transmission of less than 1x10-3 cm3m-2d-1bar-1.
In addition, the films must be stabilized against environmental effects such as UV light, high and low temperatures, and rain, and also against mechanical stresses.
Using the state-of-the-art laminating plant at the Fraunhofer IVV, barrier films can be coated with hybrid polymer lacquers to produce high-barrier laminates. Our many years of experience developing barrier films means that we can customize and measure the water vapor and oxygen transmission and the mechanical stability of the barrier films.
*Wp = Watt peak; nominal power of a solar panel