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E12.01 - Developing Indium-Free High Performance Transparent Contacts for Photovoltaics 
April 24, 2014   10:00am - 10:30am

The drive to develop cost effective TW scale photovoltaics has generated renewed interest in the development of earth abundant transparent conducting oxides (TCOs). In short, indium-free TCOs with performance similar to indium-tin-oxide (ITO) are strongly desired. Further, material properties beyond just the conventional metrics of high transparency and low sheet resistance must be considered in developing TCO materials for next generation PV application. In particular, tunable band gaps and tunable band edge energies are necessary to optimize electrical contact to both current and emerging earth abundant absorbers. Often, the use of an additional thin interfacial (or charge transport) layer based on TCO-like materials improves PV performance as well. Accordingly, band edge energies, work function, dopability and morphology should also be considered in selecting TCOs for any specific PV absorber. We will demonstrate this through examples taken largely from our prior and ongoing research, a few of which are summarized next. Amorphous Zinc-Tin-Oxide (a-ZTO) is a work function tunable, but low conductivity material, that has been demonstrated utility as a charge transport layer. Crystalline Ga-doped (Zn,Mg)O is a band gap tunable TCO where the conduction band minimum (CBM) energy can be tuned over a 0.3 eV range by varying the Mg content from 0 to 30%, albeit with reduced conductivity as the Mg content increases. Sputtered SnO TCOs are being developed with the goal of making inexpensive and chemically robust SnO a viable TCO for device applications that can not tolerate the high temperatures used in making F-doped SnO by pyrolytic decomposition processes. Finally, Nb-doped anatase TiO provides a potential high index of refraction TCO. Finally, our approach to TCO materials development generally begins with a broad exploration of the relevant materials and synthesis space. This is most often done using combinatorial composition gradient samples (libraries) grown by co-sputtering. The benefits and challenges of such high-throughput approaches will also be discussed.

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Keynote Address
Panel Discussion - Different Approaches to Commercializing Materials Research
Business Challenges to Starting a Materials-Based Company
Fred Kavli Distinguished Lectureship in Nanoscience
Application of In-situ X-ray Absorption, Emission and Powder Diffraction Studies in Nanomaterials Research - From the Design of an In-situ Experiment to Data Analysis