All-optical augmentation of solar cells using a combination of up- and downconversion

We acknowledge EPSRC and the Winton Programme for the Physics of Sustainability for funding. This work was supported by a Marie Sklodowska Curie Individual Fellowship (705113). T.W.S. acknowledges the Australian Research Council for a Future Fellowship (FT130100177). This work was supported by the Australian Research Council (Centre of Excellence in Exciton Science CE170100026).