Multiple-exciton generation—a process in which multiple charge-carrier pairs are generated from a single optical excitation—is a promising way to improve the photocurrent in photovoltaic devices and offers the potential to break the Shockley–Queisser limit. One-dimensional nanostructures, for example nanorods, have been shown spectroscopically to display increased multiple exciton generation efficiencies compared with their zero-dimensional analogues. Here we present solar cells fabricated from PbSe nanorods of three different bandgaps. All three devices showed external quantum efficiencies exceeding 100% and we report a maximum external quantum efficiency of 122% for cells consisting of the smallest bandgap nanorods. We estimate internal quantum efficiencies to exceed 150% at relatively low energies compared with other multiple exciton generation systems, and this demonstrates the potential for substantial improvements in device performance due to multiple exciton generation.

NPG
dx.doi.org/10.1038/ncomms9259
Nature Commun.
LMPV
Hybrid Solar Cells

Davis, N.J.L.K, Böhm, M.L, Tabachnyk, M, Wisnivesky, F, Jellicoe, T.C, Ducati, C, … Greenham, N.C. (2015). Multiple-exciton generation in lead selenide nanorod solar cells with external quantum efficiencies exceeding 120%. Nature Commun., 6(Article number: 8259), 1–7. doi:10.1038/ncomms9259