We show that nanoimprinting can be robust and reliable enough to be compatible with device optimization procedure. This is enabled by a method for producing nanoimprint master stamps using block copolymer lithography. This method is not only robust and low cost but it also allows patterning with nanometer size features over centimeter scale area. The large number of stamps easily produced in parallel are used to fabricate organic solar cells with controlled interpenetrating heterojunction. The power conversion efficiency is shown to increase with the pattern depth reaching a two fold increase for only similar to 35 nm deep pattern. (C) 2011 Elsevier B.V. All rights reserved.

A family of block copolymers featuring dynamically controlled compositions is presented. These copolymers, termed ‘‘quasi-block copolymers’’ (q-BCP), consist of a supramolecular polymer as one of the blocks. A conventional polymer end-capped with a functionality that is complementary to the supramolecular monomer is used to terminate the supramolecular block, giving rise to a block copolymer architecture. In this work we have utilized N,N’-2,4-bis((2-ethylhexyl)ureido)toluene (EHUT) as the supramolecular monomer and employed two types of modified 2,4-bis(ureido)toluene polystyrenes as the end-functionalized conventional polymer. Solution viscosity measurements with different solvent compositions and DSC analysis of poly(EHUT)/functionalized-PS blends provide compelling evidence for the formation of self-assembled q-BCP structures both in solution and in the melt. The qualitative role of chain stoppers on the molecular weight distribution is studied by simulations.

The creation of ordered nanoparticle assemblies is one of the main prerequisites for the utilization of nanoparticles in advanced device applications. However, while considerable progress has been made in the precision synthesis of high quality, uniform nanoparticles of different compositions, sizes and shapes, our ability to organize them into ordered structures still faces major challenges. This Feature Article focuses on a facile approach developed in recent years for the fabrication of two-dimensionally organized nanoparticle assemblies, which is based on patterning as a simple and straightforward assembly mechanism and on block copolymer films as easily created templates.