title: Enhanced carrier multiplication in engineered quasi-type-II quantum dots.
abstract: One process limiting the performance of solar cells is rapid cooling (thermalization) of hot carriers generated by higher-energy solar photons. In principle, the thermalization losses can be reduced by converting the kinetic energy of energetic carriers into additional electron-hole pairs via carrier multiplication (CM). While being inefficient in bulk semiconductors this process is enhanced in quantum dots, although not sufficiently high to considerably boost the power output of practical devices. Here we demonstrate that thick-shell PbSe/CdSe nanostructures can show almost a fourfold increase in the CM yield over conventional PbSe quantum dots, accompanied by a considerable reduction of the CM threshold. These structures enhance a valence-band CM channel due to effective capture of energetic holes into long-lived shell-localized states. The attainment of the regime of slowed cooling responsible for CM enhancement is indicated by the development of shell-related emission in the visible observed simultaneously with infrared emission from the core.
authors.affiliation: Center for Advanced Solar Photophysics, Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA.
authors.forename: Claudiu M
authors.initials: CM
authors.lastname: Cirloganu
authors.affiliation: Center for Advanced Solar Photophysics, Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA.
authors.forename: Lazaro A
authors.initials: LA
authors.lastname: Padilha
authors.affiliation: Department of Chemical Engineering, New Mexico State University, Las Cruces, New Mexico 88003, USA.
authors.forename: Qianglu
authors.initials: Q
authors.lastname: Lin
authors.affiliation: Center for Advanced Solar Photophysics, Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA.
authors.forename: Nikolay S
authors.initials: NS
authors.lastname: Makarov
authors.affiliation: Center for Advanced Solar Photophysics, Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA.
authors.forename: Kirill A
authors.initials: KA
authors.lastname: Velizhanin
authors.affiliation: Department of Chemical Engineering, New Mexico State University, Las Cruces, New Mexico 88003, USA.
authors.forename: Hongmei
authors.initials: H
authors.lastname: Luo
authors.affiliation: Center for Advanced Solar Photophysics, Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA.
authors.forename: Istvan
authors.initials: I
authors.lastname: Robel
authors.affiliation: Center for Advanced Solar Photophysics, Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Pietryga
authors.affiliation: Center for Advanced Solar Photophysics, Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA.
authors.forename: Victor I
authors.initials: VI
authors.lastname: Klimov