Semiconducting perovskite oxides are made from earth-abundant, non-toxic elements, can be synthesized in high quality heterostructures, and have electronic properties that can be tuned through doping. While these properties make them promising candidates for solar energy conversion, fundamental scientific insights, such as understanding the mechanisms that limit recombination lifetime of photoexcited carriers, are necessary before complex oxides can be utilized for efficient solar energy conversion. The intellectual mission of this project is to identify strategies to maximize photoexcited carrier lifetime and mobility using a combination of advanced thin film deposition and ultrafast spectroscopy. Thin film heterostructures consisting of the ABO3 perovskite structure, where A is a rare earth or alkaline earth ion and B is a transition metal ion (A = Sr, La, Eu; B = Cr, Fe), will be synthesized using oxide molecular beam epitaxy. Temperature-dependent time resolved terahertz spectroscopy (TRTS), UV/visible transient absorption (TA) spectroscopies, and Hall effect measurements will be used to probe dynamics of photoexcited carriers and mobility in the perovskite thin films. Through this detailed study of perovskite photophysics, this work will lay the scientific foundation for a new generation of oxide-based solar energy conversion devices.
Broader Impact
This project will provide a rational basis for designing and selecting new perovskite oxides with long lifetimes, high carrier mobilities, and optimal band gaps for solar energy conversion. Availability of efficient, low-cost, clean, and sustainable photovoltaics and photocatalysts made from earth-abundant, non-toxic materials would have transformative impact on the US energy portfolio. The project will advance scientific education through activities including the training of graduate and undergraduate students in materials synthesis and characterization techniques, student participation in scientific conferences, and in-class demonstrations of thin film deposition and ultrafast spectroscopy equipment. Outreach will also extend to pre-college students by the PIs? continued participation in mentoring local high school teachers through NSF RET and university-initiated programs. These programs are particularly beneficial for underrepresented groups since most teachers are from the School District of Philadelphia, whose student body is over 80% minorities.
