Scientists at South Dakota State University (SDSU) are working with new materials they say can be used to make devices to convert sunlight to electricity cheaper and more efficiently. Assistant professor Qiquan Qiao in SDSU's Department of Electrical Engineering and Computer Science said so-called organic photovoltaics, or OPVs, are less expensive to produce than traditional devices for harvesting solar energy.
The new technology is sometimes referred to as "molecular electronics" or "organic electronics" - "organic" because it relies on carbon-based polymers and molecules as semiconductors, rather than inorganic semiconductors such as silicon. Organic photovoltaics comprise thin films of semiconducting organic compounds that can absorb photons of solar energy. Typically an organic polymer, or a long, flexible chain of carbon-based material is used as a substrate on which semiconducting materials are applied as a solution, using a technique similar to inkjet printing.
According to Qiao, the research at SDSU focuses on new materials with variable band gaps. The band gap determines how much solar energy the photovoltaic device can absorb and convert into electricity. SDSU's scientists plan to use the variable band gap polymers to build what are called multi-junction polymer solar cells or photovoltaics. These devices use multiple layers of polymer/fullerene films "tuned" to absorb different spectral regions of solar energy. Ideally, photons that are not absorbed by the first film layer pass through to be absorbed by the following layers. This means the devices can harvest photons from ultraviolet to visible to infrared, efficiently converting the full spectrum of solar energy to electricity.
