Mike McGehee, Stanford University, Robert D. Miller, IBM Almaden Research Center, Joe DeSimone, University of North Carolina
Highlight from Stanford MRSEC 0213618
A major effort in CPIMA has been to control and characterize interfacial charge transport in directed nanoassemblies. Such research is motivated by basic issues that relate to the performance of organic electronic devices, including photovoltaics, field-effect transistors, biological sensors, and memory elements. This highlight focuses on recent activity in photovoltaics. Prior work in CPIMA by McGehee in collaboration with Miller has demonstrated that poly(3-hexylthiophene) (P3HT) has much larger charge carrier mobility when confined in straight nanopores than when confined in disordered nanopores. In these initial experiments, Miller fabricated templates using diblock copolymers and reactive ion etching with varying pore size, periodicity, and pore depth. The efficiency of straight nanopore bulk heterojunction solar cells greatly benefited from this higher mobility. In current work, McGehee has collaborated with Joe DeSimone to fabricate vertical nanopore titania by imprinting sol-gel titania using perfluoropolyether-based molds. These titania nanostructures were then used to make vertical nanopore bulk heterojunction cells, as shown in the figure prior to infiltration of P3HT. The templating method allows for variation in pore size, periodicity, and depth while also allowing suitable modifications of the titania-P3HT interface in a separate step. From IRG-3
