Highly Efficient Organic Solar Cells Using Low Band Gap Polymers and Novel Acceptor Materials

Photovoltaics is a promising clean tech approach to energy production. Organic solar cells show particular promise because they have the potential for light-weight, flexible devices with potentially low material and production costs. However, current donor materials used in organic solar cells do not absorb photons in large portions of the solar spectrum, thereby leading to inefficient photon harvesting. In addition, the molecular orbitals of current fullerene acceptor materials have a large energy offset compared to the donor polymers. These problems with the donor and acceptor materials leads to low photocurrents and low voltages, respectively, and thus to unacceptably low power conversion efficiencies. To address the low conversion efficiency, this project will synthesize low band gap polymers to enhance photon absorption and thereby increase the photocurrent. These polymers will be combined with Trimetasphere® carbon nanomaterials (TMS), which are endohedral metallofullerenes consisting of a C80 cage enclosing a trimetal nitride cluster. These nanomaterials can significantly enhance the photo-voltage of devices through better molecular orbital alignment of donor and acceptor material. Commercial Applications and other Benefits as described by the awardee: The combination of improved photocurrents and enhanced photo-voltages should lead to organic solar cell devices with commercially viable power conversion efficiencies. Applications range from rooftop photovoltaic systems to light weight, flexible solar cells integrated into tents, textiles, and small electronic devices (i.e., cell phones, PDAs, etc.).