(4cs) Nanoscale Semiconductors for Energy Conversion

Inorganic semiconductors have a proven track record for high performance electronic devices.  However, they are difficult to manufacture inexpensively and the processes used to form them are do not scale well to large-area devices such as photovoltaics, displays, and sensors. Crystallization of inorganic semiconductors requires high temperature treatments which force trade-offs between device performance, fabrication costs and compatibility with flexible substrates amenable to roll-to-roll processing. Solution-based processes such as spin coating, spray-coating or inkjet printing combined with clever materials design can introduce lower cost alternatives to conventional technologyies but high perfomance must be achieved.  Colloidal nanocrystals and molecular compounds have emerged as promising alternatives that can be deposited using inexpensive, high-throughput methods.  Such semiconductor materials not only have the benefit of solution processability, they also offer optical and electronic properties that can be tuned based on size and structure.  It has also been demonstrated that the performance of these materials can approaches that of traditionally manufactured technologies for electronic and optoelectronic applications.

A major concern in nanoscale materials is the increased role of interfaces.  For example, can good charge transport be achieved in highly granular materials?  Recent breakthroughs in surface passivation techniques for nanomaterials have opened a wide variety of techniques to facilitate charge transport in nanocrystalline thin films by using molecular compounds.  These compounds can link grains electronically as well as modulate their mobility, carrier concentration, conduction type, and optical properties.  These technological breakthroughs can be exploited to design interfaces in granular materials from the bottom up.  Gaining control of interfaces in complex systems can enable the engineering of energy flows.  This concept could be used to control electron and hole flow in photovoltaics or help isolate heat and charge carrier flows in thermoelectrics. By utilizing interface engineering, the performance of these materials could match or exceed the performance of traditionally manufactured counterparts.

Studies of nanocrystal-based solar cells, transport in solution processed films based on colloidal nanocrystals and inorganic molecular semiconductors, and future research plans will be discussed.

Selected Publications

Panthani, M. G.; Akhavan, V.; Goodfellow, B.; Schmidtke, J. P.; Dunn, L.; Dodabalapur, A.; Barbara, P. F.; Korgel, B. A. "Synthesis of CuInS₂, CuInSe₂, and Cu(In_XGa_1-X)Se₂ (CIGS) Nanocrystal "Inks" for Printable Photovoltaics.” Journal of the American Chemical Society, 130 (49), 16770-16777 (2008).

Panthani, M. G.; Hessel, C. M.; Reid, D.; Casillas, G.; Jose-Yacaman, M.; Korgel, B. A. “Graphene-Supported High-Resolution TEM and STEM Imaging of Silicon Nanocrystals and their Capping Ligands.” J Phys Chem C,  116 (42), 22463-22468 (2013).

Panthani, M.G.; Stolle, C.J.; Reid, D.K.; Rhee, D.J.; Harvey, T.B.; Akhavan, V.A.; Yu, Y.; Korgel, B.A. “CuInSe₂ Quantum Dot Solar Cells with High Open Circuit Voltage,” submitted.

Panthani, M.G.; Khan, T.; Reid, D.K.; Hellebusch, D.J.; Rasch, M.; Maynard, J.; Korgel, B.A. “CuInSe_XS_2-X Quantum dots for Biological Imaging,”manuscript in preparation.

Panthani, M. G.; Korgel, B. A. "Nanocrystals for electronics." Annual review of chemical and biomolecular engineering,  3, 287-311 (2012).

Holmberg, V. C.; Panthani, M. G.; Korgel, B. A. “Phase Transitions, Melting Dynamics, and Solid-State Diffusion in a Nano Test Tube.” Science,326 (5951), 405-407 (2009).

Steinhagen, C.; Panthani, M. G.; Akhavan, V.; Goodfellow, B.; Koo, B.; Korgel, B. A. “Synthesis of Cu₂ZnSnS₄ Nanocrystals for Use in Low-Cost Photovoltaics.” Journal of the American Chemical Society,  131 (35), 12554-12555 (2009).

Akhavan, V. A.; Panthani, M. G.; Goodfellow, B. W.; Reid, D. K.; Korgel, B. A. “Thickness-limited performance of CuInSe nanocrystal photovoltaic devices.” Optics express,18 Suppl 3, A411-20 (2010).

Stolle, C. J.; Panthani, M. G.; Harvey, T. B.; Akhavan, V. A.; Korgel, B. A. “Comparison of the Photovoltaic Response of Oleylamine and Inorganic Ligand-Capped CuInSe₂ Nanocrystals.”  ACS Applied Materials & Interfaces, 4 (5), 2757-2761 (2012).