title: Auger Up-Conversion of Low-Intensity Infrared Light in Engineered Quantum Dots.
abstract: One source of efficiency losses in photovoltaic cells is their transparency toward solar photons with energies below the band gap of the absorbing layer. This loss can be reduced using a process of up-conversion whereby two or more sub-band-gap photons generate a single above-gap exciton. Traditional approaches to up-conversion, such as nonlinear two-photon absorption (2PA) or triplet fusion, suffer from low efficiency at solar light intensities, a narrow absorption bandwidth, nonoptimal absorption energies, and difficulties for implementing in practical devices. Here we show that these deficiencies can be alleviated using the effect of Auger up-conversion in thick-shell PbSe/CdSe quantum dots. This process relies on Auger recombination whereby two low-energy, core-based excitons are converted into a single higher-energy, shell-based exciton. Compared to their monocomponent counterparts, the tailored PbSe/CdSe heterostructures feature enhanced absorption cross-sections, a higher efficiency of the "productive" Auger pathway involving re-excitation of a hole, and longer lifetimes of both core- and shell-localized excitons. These features lead to effective up-conversion cross-sections that are more than 6 orders of magnitude higher than for standard nonlinear 2PA, which allows for efficient up-conversion of continuous wave infrared light at intensities as low as a few watts per square centimeter.
authors.affiliation: Center for Advanced Solar Photophysics, Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Nikolay S
authors.initials: NS
authors.lastname: Makarov
authors.affiliation: Center for Advanced Solar Photophysics, Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Qianglu
authors.initials: Q
authors.lastname: Lin
authors.affiliation: Center for Advanced Solar Photophysics, Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Pietryga
authors.affiliation: Center for Advanced Solar Photophysics, Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: István
authors.initials: I
authors.lastname: Robel
authors.affiliation: Center for Advanced Solar Photophysics, Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Victor I
authors.identifier: 0000-0003-1158-3179
authors.initials: VI
authors.lastname: Klimov
keywords: Auger recombination; Auger up-conversion; biexciton; core/shell PbSe/CdSe quantum dot; single exciton; trion; two-photon absorption; up-conversion