Research

Organic Semiconductors (2009-current)

Organic semiconductors are an emerging technology that promises to revolutionize electronics and computing, especially in light-emitting diodes. In particular, we are examining prototypical semiconductors (tetracene, rubrene, pentacene) which have excellent electronic properties, but whose interfacial structure limits its adoption into modern displays and devices. We have developed a means for chemically reacting the surface via the classic Diels-Alder reaction (via a vapor/surface reaction) and use a variety of surface analysis techniques (XPS, PM-IRRAS, MALDI) to study the reacted surface. Device and materials properties of functionalized acenes are examined to discern their performance improvement.

From a chemistry and fundamental scientific standpoint, the reactions of these materials are even more fascinating. Solution based precedence has little predictive power when reacting a solid organic substrate. Likewise, many of the properties unique to molecular solids (weak intermolecular forces, molecular anisotropy, etc.) mean the reaction of these surfaces bear little resemblance to their inorganic counterparts. Effectively the factors determining reactivity must be reevaluated with these surfaces.

In conjunction with these classical transistor materials, the group is now looking at improving OLED interfaces by developing an interlayer that can be applied chemically on the surface of common electron transport layers. Similar chemical challenges must be surmounted and the group develops chemistry from solution phase, to surface reaction, to device optimized conditions.

Photochromophore-Induced Electronic Effects (2008-2017)

Applying a self-assembled monolayer (SAM) to a gold surface is an effective means for altering the Fermi level of that species (as measured by the work function). Judiciously done, this can result in alignment of the metal's energy levels with those of the organic semiconductor active element. Such alignment can decrease contact resistance and results in dramatically decreased threshold voltages and up to six orders of magnitude increases in efficiencies in devices such as organic solar cells, organic light-emitting diodes, and organic field effect transistors.

We examined this phenomena in the context of a stimuli-induced response. By including a photochromic (light responsive) molecule in the monolayer, we controllably and reversibly altered the Fermi level of the surface. Spectroscopic studies of the molecular structure were correlated to the changes in the metal's Fermi level.

After years of synthesis and extensive studies on surface spectroscopy and device behavior, this project was ended to focus the group on the rich field of surface chemistry on organic semiconductors.

Surface Based Metal Organic Frameworks (MOFs) (2009-2012)

This project studied how the surface energy and terminal groups within a monolayer impact the adhesion of MOFs to surfaces. This project was discontinued in 2012.

Molecule Based Patterning (2009-2011)

The project examined how tethered catalysts could pattern the surfaces. This brief foray was discontinued in 2011.