A mechanistic understanding of processing additive-induced efficiency enhancement in bulk heterojunction organic solar cells.

The addition of processing additives is a widely used approach to increase power conversion efficiencies for many organic solar cells. We present how additives change the polymer conformation in the casting solution leading to a more intermixed phase-segregated network structure of the active layer which in turn results in a 5-fold enhancement in efficiency.

Tunneling characteristics of Au-alkanedithiol-Au junctions formed via nanotransfer printing (nTP).

Construction of permanent metal-molecule-metal (MMM) junctions, though technically challenging, is desirable for both fundamental investigations and applications of molecule-based electronics. In this study, we employed the nanotransfer printing (nTP) technique using perfluoropolyether (PFPE) stamps to print Au thin films onto self-assembled monolayers (SAMs) of alkanedithiol formed on Au thin films. We show that the resulting MMM junctions form permanent and symmetrical tunnel junctions, without the need for an additional protection layer between the top metal electrode and the molecular layer.

Metal-molecule-metal junctions via PFPE assisted nanotransfer printing (nTP) onto self-assembled monolayers.

We report a simple method to form metal-molecule-metal junctions (MMMs) via nanotransfer printing with low surface energy perfluoropolyether (PFPE) based stamps. Transfer printing is demonstrated onto thermally deposited metal thin film electrodes where the root-mean-squared roughness of these films is controlled by the deposition process and varies by 40% or more. Transfer of Au and Co thin films is reported onto Au/SAM and Co/SAM electrodes in well-ordered, 200 nm MMM arrays; furthermore, nickel nanotransfer printing is shown for the first time in the construction of 200 nm arrays of Ni/SAM/Ni junctions.

Comprehensive investigation of self-assembled monolayer formation on ferromagnetic thin film surfaces.

We report a simple, universal method for forming high surface coverage SAMs on ferromagnetic thin (< or =100 nm) films of Ni, Co, and Fe. Unlike previous reports, our technique is broadly applicable to different types of SAMs and surface types. Our data constitutes the first comprehensive examination of SAM formation on three different ferromagnetic surface types using two different surface-binding chemistries (thiol and isocyanide) under three different preparation conditions: (1) SAM formation on electroreduced films using a newly developed electroreduction approach, (2) SAM formation on freshly evaporated surfaces in the glovebox, and (3) SAM formation on films exposed to atmospheric conditions beforehand.