Techniques for the Molecular Design of Push-Pull Polymers towards Enhanced Organic Photovoltaic Performance

Organic photovoltaics (OPVs) hold the great promise of providing solutions towards the earth's ever-increasing energy demands. Current environmentally friendly options that have been adapted for large-scale application are primarily inorganic materials with limited sources and high materials and processing costs. Organic alternatives offer the options of inexpensive processing onto flexible, lightweight materials. The insufficient power conversion efficiencies (PCEs) as compared to the inorganic counterparts, however, drastically limit competitiveness of organic materials in the alternative energy market. Current research in the OPV field has primarily focused on maximizing efficiency through a large number of parameters from polymer design and synthesis to device processing and optimization. This review provides an outline of several current polymer design techniques and trends of push-pull and quinoid-type organic polymers to improve OPV performance. This review will highlight techniques towards improving polymer planarity not only through the choice of monomer systems, but also the decorative alkyl chains for solubility and optical property enhancement. Synthetic deviations from traditional, alternating, push-pull copolymer systems, such as ABBA tetramers to hexamers will be explored, as well as novel trends towards enhancement of polymer stability and planarity through the use of thermocleavable moieties. Predictions of the next directions for OPV design will be presented as well.