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

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DOI http://dx.doi.org/10.1038/ncomms9259
Reference N.J.L.K. Davis, M.L. Böhm, M. Tabachnyk, F. Wisnivesky, T.C. Jellicoe, C. Ducati, B. Ehrler and N.C. Greenham, Multiple-exciton generation in lead selenide nanorod solar cells with external quantum efficiencies exceeding 120%, Nature Commun. 6, Article number: 8259: 1-7 (2015)
Group Hybrid Solar Cells

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.