Structure Measurements for Polymer-Fullerene Solar Cells
Organic photovoltaic (OPV) technology has the potential to lower the cost of solar power by enabling solar cell fabrication using high-throughput printing techniques. In bulk heterojunction (BHJ) OPV devices, the power conversion efficiency is widely thought to depend on the morphology of the polymer absorber and the fullerene electron acceptor, but robust correlations have been elusive. The first step toward correlation is the collection of quantitative structural information, which can be done using a variety of measurement methods. This talk will include several structure measurement themes including interface composition, order and orientation, solubility and miscibility, and nanoscale morphology.
A particular focus will be our recent work to establish a link between bimolecular recombination and microstructure/morphology. Very few polymer-fullerene BHJ activelayers exhibit slower-than-Langevin charge carrier recombination, which is a requirement for fabricating thick active layers (> 100 nm) while maintaining high fill factors. In collaboration with the Mozer lab at Wollongong, we evaluate a variety of hypotheses related to nanoscale film structure in an attempt to determine why some special systems exhibit this unusual and desirable feature.