Solar Energy Materials and Solar Cells, Feb 1, 2016
Abstract Arrays of closely packed nanocrystals show interesting properties that can be exploited ... more Abstract Arrays of closely packed nanocrystals show interesting properties that can be exploited to induce new features in nanostructured optoelectronic devices. In this work we study, by first principles calculations, effects induced on near band-edge states and on carrier multiplication by nanocrystals interplay. By considering both hydrogenated and oxygenated structures, we prove that interaction between silicon nanocrystals can alter both the energy gap of the system and dynamics of excited states with a relevance that depends on the nanocrystal–nanocrystal separation, on nanocrystals orientation and on nanocrystals surface properties.
Steven Weinberg, Nobel Prize in Physics, in his 1990\u2019s book said \u201cAs far as I know ther... more Steven Weinberg, Nobel Prize in Physics, in his 1990\u2019s book said \u201cAs far as I know there has never been a case of open falsification of data in physics\u201d. The numerous scandals exploded in this first part of the millennium joined forces immediately to prove him wrong. In recent years, in fact, false discoveries, plagiarism, manipulation, exaggerated results are so increased that many observers have concluded that not only strategies must be implemented to curb the phenomenon, but that we must also question the actual evolution in the structure of scientific research
We present density functional theory calculations of carrier multiplication processes in a system... more We present density functional theory calculations of carrier multiplication processes in a system of strongly coupled silicon nanocrystal
Although silicon is the most widely used material in microelectronics, photonics and photovoltaic... more Although silicon is the most widely used material in microelectronics, photonics and photovoltaics, in recent years concerns about the evolu-tion of these sectors have been raised which seem related to funda-mental materials and processing aspects. Example are the limitations of the operating speed of microelectronic devices due to the intercon-nect, the lack of optical second-order nonlinearities in bulk silicon, the necessity to improve the efficiency in solar cells. Silicon based systems with new functionalities able to solve these and other prob-lems are highly desirable. In the last years, our group has developed new theoretical tools to study structural, electronic and optical proper-ties of silicon based systems, in particular silicon nanostructures. Our analyses have permitted to predict new properties of silicon, thus opening new possibilities for applications of this material in different technological fields. Here we review our main results
Silicon Quantum Dots in Photovoltaic Devices: Device Fabrication, Characterization and Comparison... more Silicon Quantum Dots in Photovoltaic Devices: Device Fabrication, Characterization and Comparison of Materials Corresp. author: Philipp Löper, philipp.loeper@ise.fraunhofer.de, Co-authors: Marica Canino, Juliá Lopez-Vidrier, Manuel Schnabel, Anke Witzky, Michele Belletato, Marco Allegrezza, Daniel Hiller, Andreas Hartel, Sebastian Gutsch, Sergi Hernandez, Jan Valenta, Roberto Guerra, Stefano Ossicini, Blas Garrido, Stefan Janz, Margit Zacharias Affiliation: Fraunhofer ISE, Heidenhofstr. 2, D-79110 Freiburg, Germany, Phone: +497614588-5021 Fax: -9250, CNRIMM, Via Gobetti 101, I-Bologna, Italy, MIND-INUB, Universitat de Barcelona, Martí i Franquès 1, E-08028 Barcelona, Spain, IMTEK, University Freiburg, Georges-Koehler-Allee 103, D-79110 Freiburg, Germany, Charles University Prague, Ke Karlovu 3, CZ-121 16 Prague 2, Czech Republic, Università di Modena e Reggio Emilia, via Giovanni Amendola, 2, I-42100 Reggio Emilia, Italy
A systematic theoretical study of the work function behavior for Si1−xGex heterostructures over t... more A systematic theoretical study of the work function behavior for Si1−xGex heterostructures over the whole composition range, from Si (x = 0) to Ge (x = 1), is presented. Our results, obtained through Density Functional Theory calculations and in good agreement with experimental evidences, show that increasing the Ge content lowers the work function value. We find that in order to exactly reproduce this behaviour in relation to the work function of pure Ge and Si systems and their concentrations, a deviation from the linear Vegard's rule is necessary. However, the calculated bowing parameter is very small, thus making the simple linear interpolation a valid approximation to obtain the work function of complex SiGe alloys.
Solar Energy Materials and Solar Cells, Feb 1, 2016
Abstract Arrays of closely packed nanocrystals show interesting properties that can be exploited ... more Abstract Arrays of closely packed nanocrystals show interesting properties that can be exploited to induce new features in nanostructured optoelectronic devices. In this work we study, by first principles calculations, effects induced on near band-edge states and on carrier multiplication by nanocrystals interplay. By considering both hydrogenated and oxygenated structures, we prove that interaction between silicon nanocrystals can alter both the energy gap of the system and dynamics of excited states with a relevance that depends on the nanocrystal–nanocrystal separation, on nanocrystals orientation and on nanocrystals surface properties.
Steven Weinberg, Nobel Prize in Physics, in his 1990\u2019s book said \u201cAs far as I know ther... more Steven Weinberg, Nobel Prize in Physics, in his 1990\u2019s book said \u201cAs far as I know there has never been a case of open falsification of data in physics\u201d. The numerous scandals exploded in this first part of the millennium joined forces immediately to prove him wrong. In recent years, in fact, false discoveries, plagiarism, manipulation, exaggerated results are so increased that many observers have concluded that not only strategies must be implemented to curb the phenomenon, but that we must also question the actual evolution in the structure of scientific research
We present density functional theory calculations of carrier multiplication processes in a system... more We present density functional theory calculations of carrier multiplication processes in a system of strongly coupled silicon nanocrystal
Although silicon is the most widely used material in microelectronics, photonics and photovoltaic... more Although silicon is the most widely used material in microelectronics, photonics and photovoltaics, in recent years concerns about the evolu-tion of these sectors have been raised which seem related to funda-mental materials and processing aspects. Example are the limitations of the operating speed of microelectronic devices due to the intercon-nect, the lack of optical second-order nonlinearities in bulk silicon, the necessity to improve the efficiency in solar cells. Silicon based systems with new functionalities able to solve these and other prob-lems are highly desirable. In the last years, our group has developed new theoretical tools to study structural, electronic and optical proper-ties of silicon based systems, in particular silicon nanostructures. Our analyses have permitted to predict new properties of silicon, thus opening new possibilities for applications of this material in different technological fields. Here we review our main results
Silicon Quantum Dots in Photovoltaic Devices: Device Fabrication, Characterization and Comparison... more Silicon Quantum Dots in Photovoltaic Devices: Device Fabrication, Characterization and Comparison of Materials Corresp. author: Philipp Löper, philipp.loeper@ise.fraunhofer.de, Co-authors: Marica Canino, Juliá Lopez-Vidrier, Manuel Schnabel, Anke Witzky, Michele Belletato, Marco Allegrezza, Daniel Hiller, Andreas Hartel, Sebastian Gutsch, Sergi Hernandez, Jan Valenta, Roberto Guerra, Stefano Ossicini, Blas Garrido, Stefan Janz, Margit Zacharias Affiliation: Fraunhofer ISE, Heidenhofstr. 2, D-79110 Freiburg, Germany, Phone: +497614588-5021 Fax: -9250, CNRIMM, Via Gobetti 101, I-Bologna, Italy, MIND-INUB, Universitat de Barcelona, Martí i Franquès 1, E-08028 Barcelona, Spain, IMTEK, University Freiburg, Georges-Koehler-Allee 103, D-79110 Freiburg, Germany, Charles University Prague, Ke Karlovu 3, CZ-121 16 Prague 2, Czech Republic, Università di Modena e Reggio Emilia, via Giovanni Amendola, 2, I-42100 Reggio Emilia, Italy
A systematic theoretical study of the work function behavior for Si1−xGex heterostructures over t... more A systematic theoretical study of the work function behavior for Si1−xGex heterostructures over the whole composition range, from Si (x = 0) to Ge (x = 1), is presented. Our results, obtained through Density Functional Theory calculations and in good agreement with experimental evidences, show that increasing the Ge content lowers the work function value. We find that in order to exactly reproduce this behaviour in relation to the work function of pure Ge and Si systems and their concentrations, a deviation from the linear Vegard's rule is necessary. However, the calculated bowing parameter is very small, thus making the simple linear interpolation a valid approximation to obtain the work function of complex SiGe alloys.
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