uri physics colloquium

Investigating the photophysics of solar energy conversion materials using ultrafast optical, X-ray, and Mössbauer spectroscopies.

Dugan Hayes, Ph.D. Department of Chemistry  ,University of Rhode Island, Kingston, RI.

Date and Time: Friday ,Nov 9th 2018 at 4 pm

Location : East Hall , Room 112

abstract

Global human power consumption represents less than 0.2% of the solar power incident upon Earth, but this clean, renewable resource remains drastically underexploited. Improving the function of solar energy conversion devices made from durable, earth-abundant materials is necessary to make solar technology an integral part of a clean, renewable energy strategy. Energy conversion in photovoltaic and photocatalytic materials begins with the formation of excitons and/or free carriers, and the fates of these transient species – whether or not they can be separated and extracted before they recombine – is what ultimately determines conversion efficiency. Thus, a thorough understanding of the dynamics of charge separation, migration, and recombination on timescales ranging from femtoseconds to microseconds is crucial for guiding the design of next-generation materials. To this end, our group employs a variety of cross-regime ultrafast transient absorption spectroscopies to characterize these dynamics. By combining ultrafast optical, terahertz, and X-ray pulses in different experimental configurations, we can probe a broad manifold of transient chemical and physical properties of materials as they evolve during photochemical or thermochemical processes. The insights gained from these techniques collectively give a picture of how solar energy conversion materials work and what properties could be targeted to improve performance. In this talk I will give an overview of optical and X-ray transient absorption spectroscopies and provide a few examples of transition metal complexes and oxides that we have studied using this technique. I will conclude with a discussion of time-resolved synchrotron radiation Mössbauer spectroscopy, an entirely novel transient absorption technique for studying solid state materials that we are currently developing in collaboration with Rhode Island College and Argonne National Laboratory.