A Kinetic Rate Model of Novel Upconversion Nanostructures for High-Efficiency Photovoltaics

We present a computational model for predicting the net solar energy conversion efficiency of a single-junction solar cell backed by a solid-state photon upconverter. We describe and model the upconversion process using a series of kinetic rate equations to calculate equilibrium populations in a single upconversion nanostructure. We determine the internal upconversion quantum efficiency of the proposed nanostructure as a function of intentionally introduced photon energy sacrifice. We integrate the results of this model with the detailed balance method for estimating solar cell efficiency to determine the optimal nanostructure design to achieve maximum net solar energy conversion efficiency for a host solar cell backed by this upconverter. We show that net efficiencies in excess of 40% could be possible for a wide-bandgap host cell using this upconversion nanostructure.