Das Physikalische Kolloquim findet jeweils dienstags, 15.30 - 17.00 Uhr, im Hauptgebäude, Raum HG 0.20, statt.

Einladung zum Physikalischen Kolloquium
Termin:           Dienstag, 12. November 2019
Zeit:                15.30 Uhr
Ort:                 LG 1a, Raum 304

"Mechanochemical Approach to Inorganic-Organic Hybrid Materials for Perovskite Solar Cells"
D. Prochowicz^1
1Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland

The recent discovery of hybrid organic-inorganic metal halide perovskites led to a renaissance of thin film photovoltaics.¹ The great diversity of hybrid perovskite compositions and preparation pathways makes them an excellent candidate for novel photovoltaic materials with unique combination of properties, the potential for low cost and easy processing along with relatively high power conversion efficiencies.² Crystallinity, density of defects and impurities are key factors for optoelectronic properties, and are also highly dependent on the materials formation processes for most inorganic semiconductors. Understanding this behaviour and the structure/property relationship is crucial for fundamental understanding of perovskite materials, and for extending their properties to other process-tolerant systems. In that context, the synthetic approach induced by mechanical forces has appeared as a new emerging methodology in materials science.³ The mechanochemical reactions in solid state offer a significant advance by avoid the use of solvent, dramatically shortening synthesis times and simultaneously increasing the purity and amount of product.

     Herein, I will demonstrate a facile mechanochemical route for the preparation of various hybrid perovskite particles for high-efficiency thin-film photovoltaics.⁴ I will also show that such approach applied for preparation of perovskite materials has advantage over a solution-based synthetic routes in terms of hysteresis and device performance.⁵ In addition, mechanochemistry allows the facile synthesis of large quantities of polycrystalline materials that is particularly well-suited for solid-state NMR studies, which can provide direct information about cation dynamics and atomic level phase compositions.⁶ These studies highlight the essential need for atomic-level characterization of photovoltaic perovskite materials and provide fundamental understanding of photovoltaic parameters in these systems and their superior stability.
References

1. M. Grätzel, Nat. Mater. 2014, 13, 838; (b) N.-G. Park, Mater. Today2015, 18, 65.
2. W. S. Yang, B.-W. Park, E. H. Jung, N. J. Jeon, Y. C. Kim, D. U. Lee, S. S. Shin, J. Seo, E. K. Kim, J. H. Noh, S. I. Seok, Science2017, 356, 1376.
3. S. L. James et. al., Chem. Soc. Rev. 2012, 41, 413.

[4] (a) D. Prochowicz, M. Franckevičius, A. M. Cieślak, S. M. Zakeeruddin, M. Grätzel, J. Lewiński, J. Mater. Chem. A2015, 3, 20772; (b) D. Prochowicz, P. Yadav, M. Saliba, M. Saski, S. M. Zakeeruddin, J. Lewiński, M. Grätzel, Sustain. Energy Fuels2017, 1, 689.

[5]  (a) D. Prochowicz, P. Yadav, M. Saliba, M. Saski, S. Zakeeruddin, J. Lewinski, M. Grätzel, ACS Appl. Mater. Interfaces, 2017, 9, 28418; (b) D. Prochowicz, P. Yadav, M. Saliba, D. J. Kubicki, M.M. Tavakoli, S. M. Zakeeruddin, J. Lewiński, L. Emsley, M. Grätzel, Nano Energy, 2018, 49, 523.
[6]  (a) D. J. Kubicki, D. Prochowicz, A. Hofstetter, S. M. Zakeeruddin, M. Grätzel, L. Emsley. J. Am. Chem. Soc.2017, 139, 14173. (b) D. J. Kubicki, D. Prochowicz, A. Hofstetter, M. Saski, P. Yadav, D. Bi, N. Pellet, J. Lewinski, S. M. Zakeeruddin, M. Grätzel, L. Emsley. J. Am. Chem. Soc. 2018, 140, 3345.
Alle Interessenten sind sehr herzlich eingeladen!
gez. Prof. Seibold
 

Einladung
zum Sondertermin im Rahmen des
Physikalischen Kolloquiums

Termin:           Dienstag, 3. September 2019
Zeit:                15.30 Uhr
Ort:                 LG 1a, Raum 304

"Porphyrins Reactions at Near Ambient Pressure"
Matus Stredansky
University of Trieste

Porphyrins represent a class of molecules of relevant biological, chemical, physical, and industrial importance and are formed by an organic macrocycle that can bind a metal ion in the center. Both the organic part, that can be chemically functionalized, and the central single metal atom can be used to control the electronic properties of the molecule. Porphyrins have been extensively investigated in the framework of surface chemistry and physics, together with their synthetic counterpart, phthalocyanines.1,2 In this talk I will present two reactions involving porphyrin macrocycles self-assembled at surfaces, both in ultra high vacuum (UHV) and at near ambient pressure (NAP) conditions. The first example is a self-metalation reaction, a process that takes place on a metal free porphyrin deposited on a metal substrate and leads to the formation of a complex between the molecule and a metal ion coming from the surface. It is a redox reaction that has been studied for many years. There are examples of this reaction conducted in UHV with different metals.3 We have explored the self-metalation of 5,10,15,20-tetraphenylporphyrin on the Pd(100) termination. In particular, we investigated the role of pre-adsorbed oxygen in UHV as a reaction promoter, allowing it to take place at temperatures below the porphyrin decomposition yield at the supporting metal surface.5 The role of oxygen in facilitating the reaction becomes even more relevant at NAP conditions, where a different mechanism allows the metalation reaction to occur at room temperature. As a second example, I will discuss a metalorganic framework formed by 5,10,15,20-tetra(4-pyridyl)21H,23H-porphyrines with two metal species. This system has already been reported for its good electrocatalytic activity in solution for oxygen evolution reaction.4 We studied the adsorption and stabilization of molecular oxygen at NAP conditions. We propose an activated adsorption mechanism and measure the associated energy barrier.7 All experimental results were obtained by means of X-ray photoelectron spectroscopy and IR-Vis sum-frequency generation spectroscopy, both in UHV and at NAP conditions.
References:

1. Auwärter, W., Écija, D., Klappenberger, F. & Barth, J. V. Porphyrins at interfaces. Nat. Chem. 7, 105–120 (2015).

2. Gottfried, J. M. Surface chemistry of porphyrins and phthalocyanines. Surf. Sci. Rep. 70, 259–379 (2015).

3. Marbach, H. Surface-Mediated in Situ Metalation of Porphyrins at the Solid–Vacuum Interface. Acc. Chem. Res. 48, 2649–2658 (2015).

4. Wurster, B., Grumelli, D., Hötger, D., Gutzler, R. & Kern, K. Driving the Oxygen Evolution Reaction by Nonlinear Cooperativity in Bimetallic Coordination Catalysts. J. Am. Chem. Soc. 138, 3623–3626 (2016).

5. A. Goldoni, P. Shinde, G.L. Montanari, G. Di Santo, M. Caputo, L. Floreano, E. D'Incecco, M. Corva, E. Vesselli, C.A. Pignedoli, D. Passerone, A. Verdini: "Water formation for self-metalation of tetraphenyl-porphyrin on an oxidized hitherto unreactive substrate as Pd(100)", in preparation.

6. F. Armillotta, E. D’Incecco, M. Corva, M. Stredansky, J.-J. Gallet, F. Bournel, A. Goldoni, A. Morgante, E. Vesselli, A. Verdini: "Room temperature self-metalation of porphyrins at the solid-gas interface", in preparation.

7. unpublished result

Alle Interessenten sind sehr herzlich eingeladen!
gez. Prof. Seibold

Einladung zum Physikalischen Kolloquium
Termin:           Dienstag, 12. November 2019
Zeit:                15.30 Uhr
Ort:                 LG 1a, Raum 304

"Mechanochemical Approach to Inorganic-Organic Hybrid Materials for Perovskite Solar Cells"
D. Prochowicz^1
1Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland

The recent discovery of hybrid organic-inorganic metal halide perovskites led to a renaissance of thin film photovoltaics.¹ The great diversity of hybrid perovskite compositions and preparation pathways makes them an excellent candidate for novel photovoltaic materials with unique combination of properties, the potential for low cost and easy processing along with relatively high power conversion efficiencies.² Crystallinity, density of defects and impurities are key factors for optoelectronic properties, and are also highly dependent on the materials formation processes for most inorganic semiconductors. Understanding this behaviour and the structure/property relationship is crucial for fundamental understanding of perovskite materials, and for extending their properties to other process-tolerant systems. In that context, the synthetic approach induced by mechanical forces has appeared as a new emerging methodology in materials science.³ The mechanochemical reactions in solid state offer a significant advance by avoid the use of solvent, dramatically shortening synthesis times and simultaneously increasing the purity and amount of product.

     Herein, I will demonstrate a facile mechanochemical route for the preparation of various hybrid perovskite particles for high-efficiency thin-film photovoltaics.⁴ I will also show that such approach applied for preparation of perovskite materials has advantage over a solution-based synthetic routes in terms of hysteresis and device performance.⁵ In addition, mechanochemistry allows the facile synthesis of large quantities of polycrystalline materials that is particularly well-suited for solid-state NMR studies, which can provide direct information about cation dynamics and atomic level phase compositions.⁶ These studies highlight the essential need for atomic-level characterization of photovoltaic perovskite materials and provide fundamental understanding of photovoltaic parameters in these systems and their superior stability.
References

1. M. Grätzel, Nat. Mater. 2014, 13, 838; (b) N.-G. Park, Mater. Today2015, 18, 65.
2. W. S. Yang, B.-W. Park, E. H. Jung, N. J. Jeon, Y. C. Kim, D. U. Lee, S. S. Shin, J. Seo, E. K. Kim, J. H. Noh, S. I. Seok, Science2017, 356, 1376.
3. S. L. James et. al., Chem. Soc. Rev. 2012, 41, 413.

[4] (a) D. Prochowicz, M. Franckevičius, A. M. Cieślak, S. M. Zakeeruddin, M. Grätzel, J. Lewiński, J. Mater. Chem. A2015, 3, 20772; (b) D. Prochowicz, P. Yadav, M. Saliba, M. Saski, S. M. Zakeeruddin, J. Lewiński, M. Grätzel, Sustain. Energy Fuels2017, 1, 689.

[5]  (a) D. Prochowicz, P. Yadav, M. Saliba, M. Saski, S. Zakeeruddin, J. Lewinski, M. Grätzel, ACS Appl. Mater. Interfaces, 2017, 9, 28418; (b) D. Prochowicz, P. Yadav, M. Saliba, D. J. Kubicki, M.M. Tavakoli, S. M. Zakeeruddin, J. Lewiński, L. Emsley, M. Grätzel, Nano Energy, 2018, 49, 523.
[6]  (a) D. J. Kubicki, D. Prochowicz, A. Hofstetter, S. M. Zakeeruddin, M. Grätzel, L. Emsley. J. Am. Chem. Soc.2017, 139, 14173. (b) D. J. Kubicki, D. Prochowicz, A. Hofstetter, M. Saski, P. Yadav, D. Bi, N. Pellet, J. Lewinski, S. M. Zakeeruddin, M. Grätzel, L. Emsley. J. Am. Chem. Soc. 2018, 140, 3345.
Alle Interessenten sind sehr herzlich eingeladen!
gez. Prof. Seibold
 

Einladung
zum Sondertermin im Rahmen des
Physikalischen Kolloquiums

Termin:           Dienstag, 3. September 2019
Zeit:                15.30 Uhr
Ort:                 LG 1a, Raum 304

"Porphyrins Reactions at Near Ambient Pressure"
Matus Stredansky
University of Trieste

Porphyrins represent a class of molecules of relevant biological, chemical, physical, and industrial importance and are formed by an organic macrocycle that can bind a metal ion in the center. Both the organic part, that can be chemically functionalized, and the central single metal atom can be used to control the electronic properties of the molecule. Porphyrins have been extensively investigated in the framework of surface chemistry and physics, together with their synthetic counterpart, phthalocyanines.1,2 In this talk I will present two reactions involving porphyrin macrocycles self-assembled at surfaces, both in ultra high vacuum (UHV) and at near ambient pressure (NAP) conditions. The first example is a self-metalation reaction, a process that takes place on a metal free porphyrin deposited on a metal substrate and leads to the formation of a complex between the molecule and a metal ion coming from the surface. It is a redox reaction that has been studied for many years. There are examples of this reaction conducted in UHV with different metals.3 We have explored the self-metalation of 5,10,15,20-tetraphenylporphyrin on the Pd(100) termination. In particular, we investigated the role of pre-adsorbed oxygen in UHV as a reaction promoter, allowing it to take place at temperatures below the porphyrin decomposition yield at the supporting metal surface.5 The role of oxygen in facilitating the reaction becomes even more relevant at NAP conditions, where a different mechanism allows the metalation reaction to occur at room temperature. As a second example, I will discuss a metalorganic framework formed by 5,10,15,20-tetra(4-pyridyl)21H,23H-porphyrines with two metal species. This system has already been reported for its good electrocatalytic activity in solution for oxygen evolution reaction.4 We studied the adsorption and stabilization of molecular oxygen at NAP conditions. We propose an activated adsorption mechanism and measure the associated energy barrier.7 All experimental results were obtained by means of X-ray photoelectron spectroscopy and IR-Vis sum-frequency generation spectroscopy, both in UHV and at NAP conditions.
References:

1. Auwärter, W., Écija, D., Klappenberger, F. & Barth, J. V. Porphyrins at interfaces. Nat. Chem. 7, 105–120 (2015).

2. Gottfried, J. M. Surface chemistry of porphyrins and phthalocyanines. Surf. Sci. Rep. 70, 259–379 (2015).

3. Marbach, H. Surface-Mediated in Situ Metalation of Porphyrins at the Solid–Vacuum Interface. Acc. Chem. Res. 48, 2649–2658 (2015).

4. Wurster, B., Grumelli, D., Hötger, D., Gutzler, R. & Kern, K. Driving the Oxygen Evolution Reaction by Nonlinear Cooperativity in Bimetallic Coordination Catalysts. J. Am. Chem. Soc. 138, 3623–3626 (2016).

5. A. Goldoni, P. Shinde, G.L. Montanari, G. Di Santo, M. Caputo, L. Floreano, E. D'Incecco, M. Corva, E. Vesselli, C.A. Pignedoli, D. Passerone, A. Verdini: "Water formation for self-metalation of tetraphenyl-porphyrin on an oxidized hitherto unreactive substrate as Pd(100)", in preparation.

6. F. Armillotta, E. D’Incecco, M. Corva, M. Stredansky, J.-J. Gallet, F. Bournel, A. Goldoni, A. Morgante, E. Vesselli, A. Verdini: "Room temperature self-metalation of porphyrins at the solid-gas interface", in preparation.

7. unpublished result

Alle Interessenten sind sehr herzlich eingeladen!
gez. Prof. Seibold

Das Physikalische Kolloquim findet jeweils dienstags, 15.30 - 17.00 Uhr, im Lehrgebäude 1 a, Raum 304, statt.

Einladung zum Physikalischen Kolloquium

Termin:           Dienstag, 2. Juli 2019
Zeit:                15.30 Uhr
Ort:                 LG 1a, Raum 304
"Status of the new ARPES beamline at ALBA: LOREA"
Massimo Tallarida
ALBA Synchrotron Light Source, Barcelona

LOREA is the ninth beamline of the ALBA synchrotron radiation source, it is devoted to electronic structure investigations by means of Angle Resolved Photo-Emission Spectroscopy (ARPES), it is under construction and will start to be operative in 2020. The beamline and of the end-station is designed to give the possibility to perform a wide range of experiments.

After an introduction to the ARPES technique I will show the design and the status of the beamline that will cover the photon energy range of 10-1000 eV, with continuously variable polarization, resolving power of more than 10⁴ in the whole range, and spot size of about 10x10 μm².

LOREA will be suitable for high resolution ARPES measurements, as well as core level spectroscopy, resonant photoemission and X-ray absorption spectroscopy.

The end-station of LOREA will be composed by a central radial distribution chamber to which all other vessels are connected, including chambers for in situ UHV deposition and characterization, high pressure deposition (Chemical Vapor Deposition, CVD, and Atomic Layer Deposition, ALD), organic molecules deposition. The 6-axis cryo-manipulator is designed to reach temperatures better than 10K.

This project is co-funded by the European Regional Development Fund (ERDF) within the Framework of the Smart Growth Operative Programme 2014-2020.

Alle Interessenten sind sehr herzlich eingeladen!
gez. Prof. Seibold
 

Einladung
zum
Physikalischen Kolloquium
Termin:           Dienstag, 14. Mai 2019
Zeit:                15.30 Uhr
Ort:                 LG 1a, Raum 304

"High-rate laser processing for advanced micro fabrication – technological aspects, new insights into the phenomena of laser matter interactions and machining"
Jörg Schille
Hochschule Mittweida, University of Applied Science

High-rate laser machining using multi-hundred Watts ultrashort pulse lasers in combination with ultrafast laser beam movements will be introduced as key technology for advanced micro fabrication. In fact, polygon-mirror based laser beam scanning at unprecedented speeds of hundreds meters per second is the core feature to bring high-average power lasers from the laboratory to production. This is valuable for power scaling in micro machining as the processing rate scales-up with both pulse repetition frequency and average laser powers. Another advantage of ultrafast laser beam moving is that detrimental machining effects, such as high thermal loads and subsequent material melting as well as laser beam shielding by plasma/particle interactions, can be avoided even for MHz-repetitive laser pulses. In this way, highrate machining can overcome the current limitations of highly-repetitive ultrashort pulses when applied at comparably slow moving speeds, thus facilitating the high processing quality of ultrashort pulses along with high removal efficiency for high-throughput and high-precision micro fabrication. In this talk, the first part deals with how the laser parameters influence efficiency, throughput and quality in material processing. This will be complemented by a brief overview about the advantages and limitations of different strategies for efficient high-throughput laser processing. Following, the key components of the High-rate laser machining technology as established at the Laserinstitut Hochschule Mittweida will be presented, namely multi-hundreds Watt ultrashort pulse lasers in combination with polygon mirror based biaxial raster-scan systems and (external) laser beam switching for exact synchronization of laser emission and ultrafast laser beam movement. In the second part of this talk, the results obtained in flexible High-rate machining will be discussed thus to demonstrate the high potential of this advanced micro machining technology for innovative industrial applications.
Alle Interessenten sind sehr herzlich eingeladen!
gez. Prof. Seibold

Der angekündigte Vortrag kann leider wegen Krankheit zu diesem Termin nicht stattfinden. Vielen Dank für Ihr Verständnis.
Einladung zum Physikalischen Kolloquium
Termin:           Dienstag, 7. Mai 2019
Zeit:                15.30 Uhr
Ort:                 LG 1a, Raum 304

"Semiconductor growth, surface passivation and morphology modification"
Jens Falta
Institute of Solid State Physics, University of Bremen Otto-Hahn-Allee 1, D-28359 Bremen

This talk will report on growth studies of a wide variety of semiconductor systems, ranging from germanium-silicon epitaxy, over wide band gap semiconductors, like cadmium selenide and gallium oxide, to organic thin films, like PTCDA, and two-dimensional materials. Additional dsorbates have been investigated for their versatile impact on growth and surface morphology modification.

The experiments have been performed using high resolution low-energy electron diffraction (SPA-LEED), x-ray photoelectron emission spectroscopy (XPS), scanning tunneling microscopy (STM), low-energy electron microscopy (LEEM) and synchrotron radiation spectroscopy (XSW, XPEEM, NEXAFS).

Alle Interessenten sind sehr herzlich eingeladen!
gez. Prof. Seibold

Einladung zum Physikalischen Kolloquium
Termin:           Dienstag, 5. Februar 2019
Zeit:                15.30 Uhr
Ort:                 Zentrales Hörsaalgebäude, Seminarraum 2
"Oxygen storage dominated three-way catalyst modeling – concepts and applicability"
Dr. Jeremias Bickel
Robert Bosch GmbH
Compared to a conventional development and calibration of automotive catalyst control and on-board diagnosis strategies, a model-assisted workflow has a high potential for decreasing the associated testing efforts and costs. At the same time, it increases adaptivity to changing legislative boundary conditions and represents an intermediate step toward the implementation of model-based control strategies. The overall efficiency of corresponding workflows is dictated by the model development and parametrization effort as well as the model accuracy and robustness. In view of finding a good tradeoff between effort and achieved accuracy, the present talk discusses the development of simplified three-way catalyst models, focusing on the description of oxygen storage processes.
Alle Interessenten sind sehr herzlich eingeladen!
gez. Prof. Seibold