Halide chemistry in future photovoltaics and solar fuels devices

Sunlight can be harvested and converted into useful energy using semiconductor–liquid junction solar cells, which generate electrical power through the transfer of electrons to molecules dissolved in solution. If two such interfacial electron‐transfer events are efficiently coupled, stable chemical bonds can be formed, an important step to powering our planet with fuels derived from renewable energy. This talk will focus on solar energy conversion systems that rely heavily on halide oxidation chemistry, and are relevant to the proposed research in The Ardo Group at UC, Irvine.



Dye‐sensitized solar cells (DSCCs) are an inexpensive alternative to traditional solid‐state inorganic photovoltaics for electricity generation. Over the course of three years (1991 – 1993) the sunlight‐toelectrical energy‐conversion efficiency of DSSCs increased by over an order of magnitude, to 10%!  However, today the world‐record energy‐conversion efficiency is only 12%. The shortcomings of current design strategies and promising alternative nanoscale molecule–material architectures designed around the complex chemistry of iodide will be presented (right figure). These DSSC architectures are not only relevant to systems that generate electricity but also those that generate fuels from sunlight. Design criteria for efficient and scalable solar fuel systems are lacking. Results from recent device physics modeling simulations will be presented that should serve as guides for engineering future systems. A rationally engineered design consists of micron‐sized Si particles/rods embedded in a proton‐exchange membrane (left figure). Three electronic device configurations will be described that each evolves H2 when immersed in aqueous hydroiodic acid (HI) and illuminated. These systems represent potentially inexpensive means of storing transient photon energy for use when sunlight is absent, via a redox flow battery, as H₂+ I₂ / I₃- → HI.

BIO:

Dr. Ardo holds a BS degree in mathematics from Towson University, an MS degree in nutrition and food science from the University of Maryland, College Park, and MA and PhD degrees in photophysical, inorganic chemistry from Johns Hopkins University.  He is currently a postdoctoral scholar in the Lewis Group at Caltech and is funded by an independent Postdoctoral Research Award through the Department of Energy’s Office of Energy Efficiency and Renewable Energy on an original research project investigating the photoelectrochemistry of solar fuels devices for hydrohalic-acid splitting.