Intermediate Band Materials for High Efficiency Solar Cells: Overview and Future Directions
Dr Jacob Krich
Physics Department at the University of Ottawa, Canada
11:30 am Monday, 30 July 2018, Virtual Reality Theatre (AR Building), Hawthorn.
Intermediate band (IB) materials are a novel class of materials that, like semiconductors, have a band gap but also have an extra set of allowed electronic levels entirely contained within the semiconductor band gap, allowing sub-gap photon absorption. Solar cells made from such materials have the potential to radically improve photovoltaic efficiencies, similar to triple-junction cells. IB materials are also being explored for use as infrared photodetectors. Current IB devices are made from three classes of materials: quantum dots, highly-mismatched alloys, and hyperdoped semiconductors, but none has simultaneously achieved high sub-gap absorption and sufficient carrier lifetime.
I will describe theoretical and experimental work to understand the material requirements for efficient IB solar cells. I will introduce a simple figure of merit that predicts the potential effectiveness of candidate IB materials for both photodetectors and solar cells in advance of device fabrication. This figure of merit captures the trade-off between enhanced absorption and enhanced recombination within an IB material, and it suggests a path toward efficient IB materials. I will give examples of promising IB material systems and of measurements and predictions of the figure of merit.
About the Speaker
Dr Krich is a condensed matter physicist in the Physics Department at the University of Ottawa. His research is focused on the theoretical understanding of materials useful for photovoltaics, spintronics, and quantum information. Developing new materials to allow high efficiency photovoltaics or novel devices requires insight into the electronic properties of materials, especially in the presence of the nearly-unavoidable disorder in real systems. A variety of techniques, from phenomenological models to ab initio calculations, are used to describe material properties and predict new useful structures.