Multiple-exciton generation in lead selenide nanorod solar cells with external quantum efficiencies exceeding 120%
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.
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