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John E. Anthony

Gill Professor of Chemistry

Professor of Chemistry
Organic Synthesis and Materials Chemistry

Office: 027 Chemistry-Physics Building
Phone: (859) 257-8844
FAX: (859) 323-1069
Email: anthony@uky.edu

B.A., Reed College, 1989. Ph. D., University of California, Los Angeles, 1994 (F. N. Diederich). Postdoctoral: UCLA 1994-96 (Y. F. Rubin). Honors and Awards: Reed College Certificate of Academic Achievement (1986, 1987); ACS Undergraduate Award in Analytical Chemistry (1988); DuPont Graduate Teaching Award (1990); Clorox Graduate Research Award (1990); American Chemical Society, Division of Organic Chemistry Fellowship, 1991-92; Camille and Henry Dreyfus New Faculty Award, 1996; NSF CAREER Award, 1999 - 2002; Gill Professorship, 2002 - 2008.

Faculty associate, Center for Applied Energy Research


 

Anthony group publications.

Aromatic molecules constitute a robust and versatile platform for the development of functional materials for electronic applications. Using a tandem organic synthesis / device analysis approach, we seek to determine structure-property relationships that lead to materials with exceptional performance in organic thin-film transistors (for flexible flat-panel displays), organic solar cells (for low-cost generation of electricity) and organic light-emitting diodes (for low-power emissive displays). Needless to say, students in my group learn a wide range of skills, from organic synthesis to device fabrication materials characterization.

Soluble functionalized acenes from naphthalene (left) to heptacene.

Larger acenes - pushing the boundaries of aromatic stability: In order to prepare useful, robust materials from aromatic compounds, we must have a thorough understanding of their physical, spectroscopic and electronic properties. In our case, since we have chosen the linearly-fused acenes as our core chromophore, this issue is complicated by a number of issues. First, acenes larger than the pentamer (pentacene) are essentially unknown. Further, acenes larger than the trimer (anthracene) suffer from low solubility and in many cases very poor stability. Under this synthesis-oriented project, we focus on the synthesis of larger acenes (hexacene, heptacene, etc.) in order to determine what types of functionalization will yield stable, characterizable materials. We have already had some success in isolating and fully characterizing (including obtaining the first reported crystal structures) a substituted heptacene and heteroheptacene. Note that the determination of these structures relied heavily on the Department's outstanding X-ray diffraction laboratory, run by Dr. Sean Parkin.



We are currently exploring new functionalization strategies to further enhance the stability of these molecules, to allow us to prepare characterizable derivatives of the heretofore unknown acenes octacene and nonacene.

Materials: This set of projects involves the specific tuning of functionalization to yield optimum performance in a variety of electronic device applications. We have developed a rough model that allows us to predict the solid-state order of acenes functionalized by our method - the fine-tuning allows us to make subtle changes that improve film morphology, electrode contacts or photostability. Following this model, we have prepared materials with record-high performance in a number of areas.

Transistors: A field-effect transistor is a three-electrode device that turns current between two of the electrodes (labeled "source" and "drain") off or on by application of voltage across the third electrode (called the "gate"). For use in organic transistors, we have obtained the best results using molecules that exhibit two-dimensional pi-stacking in the sold state.


Working with the Jackson group at Penn State, devices with hole mobility as high as 1.7 cm2/Vs have been prepared. Rather than the complicated vacuum deposition usually required to deposit un-substituted pentacenes, our materials are easily deposited by a number of solution-based methods, including dip-casting, spin-casting and drop-casting. Along with high-performance devices, the slow crystallization afforded by solution deposition yields some beautiful microscope images. The Martin group at U. Michigan has also prepared high mobility transistors, and through their ability to grow highly oriented films, has been able to observe anisotropy in the mobility of these systems.

We are lucky to have many great collaborators in this area. For example, the Loo group has found that with our anthradithiophene-class of materials, exposure of films to solvent vapor for only a few minutes will dramatically improve the device performance of the materials. We're also working closely with the Gundlach group at NIST to elucidate the properties of some substituted heteroacenes - more here soon.

Solar cells: TIPS pentacene can also be used as the donor material in organic solar cells. We've been working with the Kafafi group at the Naval Research Laboratory on vapor-deposited TIPS pentacene, and with the Malliaras group at Cornell on solution-deposited TIPS pentacene. Both of these devices are single-heterojunction solar cells, and both yield power conversion efficiencies of approximately 0.5%. The rapid reaction between TIPS pentacene and fullerene derivatives precludes the use of this material in all-solution-processed devices.


We're also working with the Malliaras group on new heteroacenes for solar cells, since the stability of these materials toward fullerenes allows solution processing of both donor and acceptor, for the formation of bulk-heterojunction solar cells. We have noted a strong correlation between film morphology and device performance in these simple cells, and have already prepared devices with efficiencies > 1.0%. Just as with TIPS pentacene films, these anthradithiophene spherulite structures yield awesome micrograph images, and in fact Matt Lloyd, one of Malliaras' graduate students, recently won the MRS "science as art" image competition with a picture of just such a structure (from a failed device, unfortunately). You can see the winning image here.

Light-emitting diodes: Using a variety of functionalized acenes, we've been able to make OLEDs that emit in a variety of colors. Working with the Kafafi group, we optimized one of our pentacene derivatives to yield a red-emitting material that exhibited very high efficiency in an Alq3-based device configuration.


I am grateful to all of my collaborators for their insight, assistance, and for being such fantastic people to work with. I also thank the support (both intellectual and financial) of our research programs by the Office of Naval Research, the Defense Advanced Projects Agency , and the Department of Homeland Security.


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