Potential and challenges of intermediate band and hot carrier solar cells

I will discuss the status of intermediate band (IB) solar cells and of a recently proposed hot carrier solar cell concept called valley photovoltaics (VPV). I will discuss the development of a trio of models, with varying computational cost, for understanding and designing advanced concept photovoltaics. I will describe Simudo, a Poisson/drift-diffusion solver for advanced PV, and use it to validate a semi-analytic model for IB devices, which allows rapid exploration of the design space. Including realistic nonradiative losses, efficient IBSCs will be easier to make with higher bandgap materials than are most commonly studied, and I will show experiments and design concepts for GaN-based IB devices. The VPV concept is that hot carriers can be maintained in and extracted from metastable valleys of the conduction band. Devices so far have JV curves with a strong S-shape and low power generation. We adapt Simudo to treat VPV and well reproduce experimental JV curves. I will discuss the various origins of the S-shape. I will introduce an equivalent circuit model for the S-shape and connect it to physics in the device, giving insight into the obstacles to achieving high efficiency.