Low Cost “ Plastic ” Solar Cells : A Dream or Reality ? ? ? :

8:30 AM Plenary Low Cost “Plastic” Solar Cells: A Dream or Reality???: Alan Heeger1; 1University of California, Santa Barbara Polymer solar cells with power conversion efficiencies in excess of 5% are demonstrated using bulk heterojunction materials. Spatial Fourier transform methods have been used to study and optimize the morphology. Light harvesting has been improved by using a novel low-bandgap conjugated polymer, with an optical energy gap of Eg~1.5 eV. Solar cells with a TiOx layer (deposited by a sol-gel process) between the active layer and the electron collecting aluminum electrode exhibit enhanced power conversion efficiency and significantly improved lifetime compared to similar devices without the TiOx layer. The use of TiOx provides several important opportunities; specifically, the TiOx layers enable higher performance from single cells, longer lifetime as a result of reduced sensitivity of the solar cell to oxygen and water vapor, and the fabrication of bulk heterojunction cells in the ‘Tandem Cell’ architecture, a multilayer structure that is equivalent to two photovoltaic cells in series.