B.A., University of Oregon, 2003. Ph.D., UC Santa Barbara (Galen D. Stucky). Postdoctoral, California Institute of Technology (Nathan S. Lewis and Harry A. Atwater). Honors and Awards: Barry M. Goldwater Scholar (2001-2003), NSF Graduate Research Fellow (2003-2006), UC Chancellors Fellow (2007), Kavli Nanoscience Institute Prize Postdoctoral Fellow (2008-2009). Dupont Young Professor (2011). At Oregon since 2010.
The Boettcher Group consists of a diverse group of chemists, physicists, and engineers who share a common passion for addressing the significant fundamental materials challenges associated with the capture and storage of solar energy. We utilize inorganic synthesis, nano and microscience, surface chemistry, simulation, physical measurement, and device fabrication to design, build and study new materials and structures. Several specific research thrusts are outlined below.
Semiconductors with nano- and microstructures designed for solar energy conversion
Inorganic semiconductors are ideal materials for solar energy conversion – many strongly absorb visible light generating long-lived excited charge carriers that can be separated and collected using interfacial electric fields. The key challenge, however, is to develop materials systems that are not only efficient, but also durable and scalable (i.e. low-cost and consisting of earth-abundant elements). The precise control of three-dimensional structure and composition will be explored as one route to achieve these goals. For example, in a traditional planar device, photogenerated carriers must traverse the entire thickness of the cell in order to be collected before recombination. This cell thickness is dictated by how much material is necessary to absorb the incoming light, ~ 1/α. In a rod-array cell, carriers must only reach the rod surface before recombination, thus enhancing the performance of materials that are charge-collection limited and broadening the range of materials suitable to achieve high efficiencies. Current projects in the group focus on the synthesis and characterization of semiconducting transition metal oxides, such as WO3, and III-V compound semiconductors, such as GaAs.
Heterogeneous Electrocatalysts for Artificial Photosynthesis
Heterogeneous Electrocatalysts for Artificial Photosynthesis. If sunlight is to provide a significant fraction of the worlds’ power consumption, methods must be developed to store solar energy at a massive scale for use when the sun doesn’t shine. Arguably, the best way to store this energy is in the form of chemical bonds. Nature does this in photosynthesis – albeit with low overall efficiencies. The goal of this research thrust is to synthesize well-defined nanoscale inorganic electrocatalysts that facilitate molecular transformations useful in energy storage (e.g. hydrogen and oxygen evolution from water) and then study fundamental structure-activity relationships. These catalysts can then be integrated with semiconductor light-absorbers to create completely inorganic artificial photosynthetic systems.
Electroactive Interfaces in Water-Splitting Systems
In multi-component inorganic water-splitting systems, photoexcited electrons and holes must traverse interfaces between different types of semiconductors and catalysts. We are working to measure and understand the fundamental properties of these interfaces, so that complete systems can be better designed.
Other research interests
Additional thrusts under development are listed in the areas below:
Earth-abundant chalcogenide semiconductors for thin film photovoltaics. (w/ Doug Keszler, Janet Tate, and John Wager at Oregon State University)
Scalable routes to multijunction (i.e. high-efficiency/ low-cost) photovoltaics.
Electrode materials/architectures for rechargeable batteries. Electrocatalysts for fuel cells.
Surface chemistry of non-traditional semiconductors for photoelectrochemistry. (sulfides, oxides, etc.)
oettcher, S. W.; Warren, E. L.; Putnam, M. C.; Santori, E. A.; Turner-Evans, D.; Kelzenberg, M. D.; Walter, M. G.; McKone, J. R.; Brunschwig, B. S.; Atwater, H. A.; Lewis, N. S. Photoelectrochemical Hydrogen Evolution Using Si Microwire Arrays. J. Am. Chem. Soc., 133, 1216-1219. 2011
Boettcher, S. W.; Spurgeon, J.M.; Putnam, M.C.; Warren, E.L.; Turner-Evans, D.B.; Kelzenberg, M.D.; Maiolo, J.R.; Atwater, H.A.; Lewis, N.S., Energy conversion properties of silicon wire-array photocathodes. Science, 327, 185. 2010.
Kelzenberg, M.D.; Boettcher, S.W.; Petykiewicz, J.A.; Turner-Evans, D.B.; Putnam, M.C.; Warren, E.L.; Spurgeon, J.M.; Lewis, N.S.; Atwater, H.A., Absorption enhancement in Si wire arrays for photovoltaic applications. Nat. Mater., 9, 239. 2010.
Schierhorn, M.; Boettcher, S. W.; Kraemer, S; Stucky, G.D.; Moskovits, M., Photoelectrochemical performance of CdSe nanorod arrays grown on a transparent conducting substrate. Nanoletters, 2009, 9(9) 3262-3267.
Boettcher, S.W.; Strandwitz, N.C.; Schierhorn, M.; Lock, N.; Lonergan, M.C.; Stucky, G.D., Tunable electronic interfaces between bulk semiconductors and ligand-stabilized nanoparticle assemblies. Nature Materials, 2007, 6(8), 592.
Boettcher, S.W.; Fan, J.; Tsung, C.K.; Shi, Q.H.; Stucky, G.D., Harnessing the sol-gel process for the assembly of non-silicate mesostructured oxide materials. Acc. Chem. Res., 2007, 40 (9), 784–792 (Cover)
Boettcher, S.W.; Berg, S.; Schierhorn, M.S., Strandwitz, N.C.; Lonergan, M.C.; Stucky, G.D., Ionic ligand mediated electrochemical charging of gold nanoparticle assemblies. Nanoletters, 2008, 8(10) 3404.
Boettcher, S.W.; Bartl, M.H.; Hu, J.G.; Stucky, G.D., Structural analysis of hybrid titania-based mesostructured composites. J. Am. Chem. Soc. 2005, 127(27), 9721.