Public Research Seminar

This Public Research Seminar is on 19 July 2012

Resonant light trapping in ultrathin films: Boosting the efficiency of a-Fe₂O₃ photoanodes for water splitting

Avner Rothschild
Department of Materials Engineering,
Technion – Israel Institute of Technology, Haifa, Israel

Location:  UNSW Building H6 – Tyree Energy Technologies Building -  Room G17
Time: 12pm - 1pm

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Semiconductor photoelectrodes for efficient solar hydrogen production by water photoelectrolysis must employ stable, non-toxic, abundant and inexpensive semiconductor visible light absorbers. Iron oxide (a-Fe₂O₃) is one of few materials meeting these requirements, but its poor transport properties present challenges for efficient charge carrier generation, separation, collection and injection. Here we show that these challenges can be addressed by means of resonant light trapping in ultrathin films designed as optical cavities. Interference effects between forward and backward propagating waves enhance light absorption in quarter-wave or, in some cases, deeper sub-wavelength films, amplifying the intensity close to the surface wherein photogenerated minority charge carriers (holes) can reach the surface and oxidize water before recombination takes place. Our approach enables efficient light harvesting in a-Fe₂O₃ films thinner than 50 nm, thereby suppressing the recombination loss and overcoming the tradeoff between light absorption and charge collection efficiencies. We show that water photo-oxidation current densities as high as 4.8 mA cm^-2 may be achieved in simple stratified structures comprising ultrathin a-Fe₂O₃ films on a reflective substrates.

BRIEF BIOGRAPHY

Avner Rothschild is an associate professor at the Department of Materials Engineering of the Technion – Israel Institute of Technology. After graduating from the Technion (BSc in Physics and in Materials Engineering in 1997, PhD in 2003) he spent three years at MIT as a postdoc in Harry Tuller’s group. In 2006 he returned back to the Technion as a faculty member. Avner is heading the Electroceramic Materials & Devices research group, working on semiconducting, ionic and mixed ionic electronic conducting oxides for applications in electronic and optoelectronic devices, gas sensors and solar cells. He is a member of the editorial board of the Journal of Electroceramics, the Technion Energy Team, and Israel’s Solar Fuels Consortium.