The paper by R. D. Schaller and V. I. Klimov demonstrates for the first time that impact ionization (II) occurs with high efficiency in PbSe nanocrystals (NCs), which can significantly enhance the power conversion efficiency of solar cells. Interband optical excitation of PbSe NCs at low pump intensities results in the formation of multiple excitons (carrier multiplication) when the pump photon energy is more than three times the band gap energy. This process, which occurs on a picosecond timescale, can be up to 100% efficient depending on the excess energy of the absorbed photon. The authors use transient absorption (TA) to monitor the conversion of highly excited excitons into biexcitons, showing that II in PbSe NCs is highly efficient and occurs in a wavelength range that has potential to significantly increase solar cell power conversion efficiency. The efficiency of II increases as the band gap energy decreases, and efficiencies as high as 118% are observed for photon energies of 3.8Eg. The study also shows that the charge transfer step in solar cells can be very fast, allowing II-generated excitons to be useful for solar power generation. The theoretical treatment of Auger effects in NCs is complex, but the authors believe that II competes with intraband relaxation in NCs. The paper concludes by discussing the potential of PbSe NCs for high-efficiency solar cells, given their size-tunable band gap and strong absorption across the ultraviolet to near-IR spectrum.The paper by R. D. Schaller and V. I. Klimov demonstrates for the first time that impact ionization (II) occurs with high efficiency in PbSe nanocrystals (NCs), which can significantly enhance the power conversion efficiency of solar cells. Interband optical excitation of PbSe NCs at low pump intensities results in the formation of multiple excitons (carrier multiplication) when the pump photon energy is more than three times the band gap energy. This process, which occurs on a picosecond timescale, can be up to 100% efficient depending on the excess energy of the absorbed photon. The authors use transient absorption (TA) to monitor the conversion of highly excited excitons into biexcitons, showing that II in PbSe NCs is highly efficient and occurs in a wavelength range that has potential to significantly increase solar cell power conversion efficiency. The efficiency of II increases as the band gap energy decreases, and efficiencies as high as 118% are observed for photon energies of 3.8Eg. The study also shows that the charge transfer step in solar cells can be very fast, allowing II-generated excitons to be useful for solar power generation. The theoretical treatment of Auger effects in NCs is complex, but the authors believe that II competes with intraband relaxation in NCs. The paper concludes by discussing the potential of PbSe NCs for high-efficiency solar cells, given their size-tunable band gap and strong absorption across the ultraviolet to near-IR spectrum.