Prof. Dr. techn. Reinhard Kienberger
Academic Research Focus
- Research in the field of ultrafast electron dynamics on the attosecond time scale to investigate intra-atomic and intra-molecular processes in the gas phase and in solids
- Time-resolved infrared spectroscopy of energy materials and nanostructures
- Development of a cavity for generating high-energy, coherent X-rays
- Advanced microscopy & SHG-CD spectroscopy of chiral films
- Time-resolved infrared spectroscopy of energy materials and nanostructures
- Development of a cavity for generating high-energy, coherent X-rays
- Advanced microscopy & SHG-CD spectroscopy of chiral films
Fields of Application
Photo-(electro)catalysis
Publications
16.
J Pittrich, K Liang, L Dörringer, R Kienberger, U Heiz, A Kartouzian, H Iglev
From molecules to materials: SHG-CD microscopy of structured chiral films Journal Article
In: Applied Surface Science, vol. 680, pp. 161331, 2025, ISSN: 0169-4332.
@article{nokey,
title = {From molecules to materials: SHG-CD microscopy of structured chiral films},
author = {J Pittrich and K Liang and L D\"{o}rringer and R Kienberger and U Heiz and A Kartouzian and H Iglev},
url = {https://www.sciencedirect.com/science/article/pii/S0169433224020464},
doi = {https://doi.org/10.1016/j.apsusc.2024.161331},
issn = {0169-4332},
year = {2025},
date = {2025-01-30},
journal = {Applied Surface Science},
volume = {680},
pages = {161331},
abstract = {The interplay between molecular and structural chirality as a function of local sample morphology determines the nonlinear optical properties of many organic and hybrid organic\textendashinorganic thin films. Here, we used second harmonic generation circular dichroism (SHG-CD) microscopy of thin molecular films of 1,1′-bi-2-naphthol (R-BINOL) as a research model. Our results show that the SHG signal measured at frequencies close to the electronic transition of BINOL molecules is resonantly enhanced by more than an order of magnitude compared to the non-resonant case. The extracted resonant SHG-CD signal is dominated by the chiral response of the molecule. In contrast, structural chirality determines the non-resonant SHG-CD images. We see clear evidence that the interference of the SHG signals caused by the molecular and structural chirality can lead to a decrease in the overall SHG intensity when both SHG signals are out of phase. These findings highlight the intricate relationship between molecular and structural chirality on the one hand and structural morphology on the other hand and pave the way for novel applications by exploiting the chiroptic properties of thin films.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The interplay between molecular and structural chirality as a function of local sample morphology determines the nonlinear optical properties of many organic and hybrid organic–inorganic thin films. Here, we used second harmonic generation circular dichroism (SHG-CD) microscopy of thin molecular films of 1,1′-bi-2-naphthol (R-BINOL) as a research model. Our results show that the SHG signal measured at frequencies close to the electronic transition of BINOL molecules is resonantly enhanced by more than an order of magnitude compared to the non-resonant case. The extracted resonant SHG-CD signal is dominated by the chiral response of the molecule. In contrast, structural chirality determines the non-resonant SHG-CD images. We see clear evidence that the interference of the SHG signals caused by the molecular and structural chirality can lead to a decrease in the overall SHG intensity when both SHG signals are out of phase. These findings highlight the intricate relationship between molecular and structural chirality on the one hand and structural morphology on the other hand and pave the way for novel applications by exploiting the chiroptic properties of thin films.
15.
D Sandner, K Sun, A Stadlbauer, M W Heindl, Q Y Tan, M Nuber, C Soci, R Kienberger, P Müller-Buschbaum, F Deschler, H Iglev
Hole Localization in Bulk and 2D Lead-Halide Perovskites Studied by Time-Resolved Infrared Spectroscopy Journal Article
In: Journal of the American Chemical Society, vol. 146, no. 29, pp. 19852-19862, 2024, ISSN: 0002-7863.
@article{nokey,
title = {Hole Localization in Bulk and 2D Lead-Halide Perovskites Studied by Time-Resolved Infrared Spectroscopy},
author = {D Sandner and K Sun and A Stadlbauer and M W Heindl and Q Y Tan and M Nuber and C Soci and R Kienberger and P M\"{u}ller-Buschbaum and F Deschler and H Iglev},
url = {https://doi.org/10.1021/jacs.4c02958},
doi = {10.1021/jacs.4c02958},
issn = {0002-7863},
year = {2024},
date = {2024-07-24},
journal = {Journal of the American Chemical Society},
volume = {146},
number = {29},
pages = {19852-19862},
abstract = {Scattering and localization dynamics of charge carriers in the soft lattice of lead-halide perovskites impact polaron formation and recombination, which are key mechanisms of material function in optoelectronic devices. In this study, we probe the photoinduced lattice and carrier dynamics in perovskite thin films (CsFAPbX3},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Scattering and localization dynamics of charge carriers in the soft lattice of lead-halide perovskites impact polaron formation and recombination, which are key mechanisms of material function in optoelectronic devices. In this study, we probe the photoinduced lattice and carrier dynamics in perovskite thin films (CsFAPbX3
14.
D Potamianos, M Schnitzenbaumer, C Lemell, P Scigalla, F Libisch, E Schock-Schmidtke, M Haimerl, C Schröder, M Schäffer, J T Küchle, J Riemensberger, K Eberle, Y Cui, U Kleineberg, J Burgdörfer, J V Barth, P Feulner, F Allegretti, R Kienberger
Attosecond chronoscopy of the photoemission near a bandgap of a single-element layered dielectric Journal Article
In: Science Advances, vol. 10, no. 26, pp. eado0073, 2024.
@article{nokey,
title = {Attosecond chronoscopy of the photoemission near a bandgap of a single-element layered dielectric},
author = {D Potamianos and M Schnitzenbaumer and C Lemell and P Scigalla and F Libisch and E Schock-Schmidtke and M Haimerl and C Schr\"{o}der and M Sch\"{a}ffer and J T K\"{u}chle and J Riemensberger and K Eberle and Y Cui and U Kleineberg and J Burgd\"{o}rfer and J V Barth and P Feulner and F Allegretti and R Kienberger},
url = {https://www.science.org/doi/abs/10.1126/sciadv.ado0073},
doi = {doi:10.1126/sciadv.ado0073},
year = {2024},
date = {2024-06-26},
journal = {Science Advances},
volume = {10},
number = {26},
pages = {eado0073},
abstract = {We report on the energy dependence of the photoemission time delay from the single-element layered dielectric HOPG (highly oriented pyrolytic graphite). This system offers the unique opportunity to directly observe the Eisenbud-Wigner-Smith (EWS) time delays related to the bulk electronic band structure without being strongly perturbed by ubiquitous effects of transport, screening, and multiple scattering. We find the experimental streaking time shifts to be sensitive to the modulation of the density of states in the high-energy region (E ≈ 100 eV) of the band structure. The present attosecond chronoscopy experiments reveal an energy-dependent increase of the photoemission time delay when the final state energy of the excited electrons lies in the vicinity of the bandgap providing information difficult to access by conventional spectroscopy. Accompanying simulations further corroborate our interpretation. Photoionization timing is exploited for detecting otherwise inaccessible high-energy region band structure features.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report on the energy dependence of the photoemission time delay from the single-element layered dielectric HOPG (highly oriented pyrolytic graphite). This system offers the unique opportunity to directly observe the Eisenbud-Wigner-Smith (EWS) time delays related to the bulk electronic band structure without being strongly perturbed by ubiquitous effects of transport, screening, and multiple scattering. We find the experimental streaking time shifts to be sensitive to the modulation of the density of states in the high-energy region (E ≈ 100 eV) of the band structure. The present attosecond chronoscopy experiments reveal an energy-dependent increase of the photoemission time delay when the final state energy of the excited electrons lies in the vicinity of the bandgap providing information difficult to access by conventional spectroscopy. Accompanying simulations further corroborate our interpretation. Photoionization timing is exploited for detecting otherwise inaccessible high-energy region band structure features.
13.
K Liang, F Ristow, K Li, J Pittrich, N Fehn, L Dörringer, U Heiz, R Kienberger, G Pescitelli, H Iglev, A Kartouzian
Negative Nonlinear CD–ee Dependence in Polycrystalline BINOL Thin Films Journal Article
In: Journal of the American Chemical Society, 2023, ISSN: 0002-7863.
@article{nokey,
title = {Negative Nonlinear CD\textendashee Dependence in Polycrystalline BINOL Thin Films},
author = {K Liang and F Ristow and K Li and J Pittrich and N Fehn and L D\"{o}rringer and U Heiz and R Kienberger and G Pescitelli and H Iglev and A Kartouzian},
url = {https://doi.org/10.1021/jacs.3c12253},
doi = {10.1021/jacs.3c12253},
issn = {0002-7863},
year = {2023},
date = {2023-12-13},
journal = {Journal of the American Chemical Society},
abstract = {Generally, the relationship between the observed circular dichroism and the enantiomeric excess in chiral systems (CD\textendashee dependence) is linear. While positive nonlinear behavior has often been reported in the past, examples of negative nonlinear (NN) behavior in CD\textendashee dependence are rare and not well understood. Here, we present a strong NN CD\textendashee dependence within polycrystalline thin films of BINOL by using second-harmonic-generation circular dichroism (SHG-CD) and commercial CD spectroscopy studies. Theoretical calculations, microscopy, and FTIR studies are employed to further clarify the underlying cause of this observation. This behavior is attributed to the changing supramolecular chirality of the system. Systems exhibiting NN CD\textendashee dependence hold promise for highly accurate enantiomeric excess characterization, which is essential for the refinement of enantio-separating and -purifying processes in pharmaceuticals, asymmetric catalysis, and chiral sensing. Our findings suggest that a whole class of single-species systems, i.e., racemate crystals, might possess NN CD\textendashee dependence and thus provide us a vast playground to better understand and exploit this phenomenon.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Generally, the relationship between the observed circular dichroism and the enantiomeric excess in chiral systems (CD–ee dependence) is linear. While positive nonlinear behavior has often been reported in the past, examples of negative nonlinear (NN) behavior in CD–ee dependence are rare and not well understood. Here, we present a strong NN CD–ee dependence within polycrystalline thin films of BINOL by using second-harmonic-generation circular dichroism (SHG-CD) and commercial CD spectroscopy studies. Theoretical calculations, microscopy, and FTIR studies are employed to further clarify the underlying cause of this observation. This behavior is attributed to the changing supramolecular chirality of the system. Systems exhibiting NN CD–ee dependence hold promise for highly accurate enantiomeric excess characterization, which is essential for the refinement of enantio-separating and -purifying processes in pharmaceuticals, asymmetric catalysis, and chiral sensing. Our findings suggest that a whole class of single-species systems, i.e., racemate crystals, might possess NN CD–ee dependence and thus provide us a vast playground to better understand and exploit this phenomenon.
12.
D Sandner, H Esmaielpour, F D Giudice, S Meder, M Nuber, R Kienberger, G Koblmüller, H Iglev
Hot Electron Dynamics in InAs–AlAsSb Core–Shell Nanowires Journal Article
In: ACS Applied Energy Materials, vol. 6, no. 20, pp. 10467-10474, 2023.
@article{nokey,
title = {Hot Electron Dynamics in InAs\textendashAlAsSb Core\textendashShell Nanowires},
author = {D Sandner and H Esmaielpour and F D Giudice and S Meder and M Nuber and R Kienberger and G Koblm\"{u}ller and H Iglev},
url = {https://doi.org/10.1021/acsaem.3c01565},
doi = {10.1021/acsaem.3c01565},
year = {2023},
date = {2023-10-05},
journal = {ACS Applied Energy Materials},
volume = {6},
number = {20},
pages = {10467-10474},
abstract = {Semiconductor nanowires (NWs) have shown evidence of robust hot-carrier effects due to their small dimensions, making them attractive for advanced photoenergy conversion concepts. Especially, indium arsenide (InAs) NWs are promising candidates for harvesting hot carriers due to their high absorption coefficient, high carrier mobility, and large effective electron-to-hole mass difference. Here, we investigate the cooling and recombination dynamics of photoexcited hot carriers in pure and passivated InAs NWs by using ultrafast near-infrared pump\textendashprobe spectroscopy. We observe reduced Auger recombination in pure InAs NWs compared to that in passivated ones and associate this with charge-carrier separation by surface band bending. Similarly, faster carrier cooling by electron\textendashhole scattering is observed in passivated InAs\textendashAlAsSb NWs at high carrier densities in excess of 1018 cm\textendash3, where hot electron lifetimes in this regime increase substantially with the pump fluence due to Auger heating. These results emphasize the importance of type-II alignment for charge-carrier separation in hot-carrier devices to suppress carrier-mediated cooling channels. In addition, a separate charge-carrier population lasting up to several nanoseconds is observed for photoexcitation of the NW shell. Despite the high conduction band offset, carrier migration is not observed in the range of 40 ps to 2 ns. This observation may open avenues for core\textendashshell NW multijunction solar cells.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Semiconductor nanowires (NWs) have shown evidence of robust hot-carrier effects due to their small dimensions, making them attractive for advanced photoenergy conversion concepts. Especially, indium arsenide (InAs) NWs are promising candidates for harvesting hot carriers due to their high absorption coefficient, high carrier mobility, and large effective electron-to-hole mass difference. Here, we investigate the cooling and recombination dynamics of photoexcited hot carriers in pure and passivated InAs NWs by using ultrafast near-infrared pump–probe spectroscopy. We observe reduced Auger recombination in pure InAs NWs compared to that in passivated ones and associate this with charge-carrier separation by surface band bending. Similarly, faster carrier cooling by electron–hole scattering is observed in passivated InAs–AlAsSb NWs at high carrier densities in excess of 1018 cm–3, where hot electron lifetimes in this regime increase substantially with the pump fluence due to Auger heating. These results emphasize the importance of type-II alignment for charge-carrier separation in hot-carrier devices to suppress carrier-mediated cooling channels. In addition, a separate charge-carrier population lasting up to several nanoseconds is observed for photoexcitation of the NW shell. Despite the high conduction band offset, carrier migration is not observed in the range of 40 ps to 2 ns. This observation may open avenues for core–shell NW multijunction solar cells.
11.
C Schröder, J Riemensberger, R Kuzian, M Ossiander, D Potamianos, F Allegrett, L Bignardi, S Lizzit, A Akil, A Cavalieri, D Menzel, S Neppl, R Ernstorfer, J Braun, H Ebert, J Minar, W Helml, M Jobst, M Gerl, E Bothschafter, A Kim, K Hütten, U Kleineberg, M Schnitzenbaumer, J V Barth, P Feulner, E Krasovskii, R Kienberger
Attosecond dynamics of photoemission over a wide photon energy range Miscellaneous
2023.
@misc{nokey,
title = {Attosecond dynamics of photoemission over a wide photon energy range},
author = {C Schr\"{o}der and J Riemensberger and R Kuzian and M Ossiander and D Potamianos and F Allegrett and L Bignardi and S Lizzit and A Akil and A Cavalieri and D Menzel and S Neppl and R Ernstorfer and J Braun and H Ebert and J Minar and W Helml and M Jobst and M Gerl and E Bothschafter and A Kim and K H\"{u}tten and U Kleineberg and M Schnitzenbaumer and J V Barth and P Feulner and E Krasovskii and R Kienberger},
url = {http://europepmc.org/abstract/PPR/PPR750080
https://doi.org/10.21203/rs.3.rs-3024896/v1},
doi = {10.21203/rs.3.rs-3024896/v1},
year = {2023},
date = {2023-10-01},
urldate = {2023-10-01},
publisher = {Research Square},
abstract = {Dynamics of photoemission from surfaces are usually studied at low photon energies (\<100 eV). Here, we report on new findings on these dynamics observed at a tungsten surface on the attosecond time scale at photon energies exceeding 100 eV, over a range of almost 50 eV. While photoemission, a fundamental process in quantum mechanics, is often described within a semiclassical three-step model, we find that even at high photon energies only a full quantum treatment in one step predicts the measured attosecond dynamics correctly. On this time scale the intuitive, mechanistic interpretation of the photoelectric effect breaks down. This underlines the necessity to further develop experimental and theoretical tools to be used in improving our understanding of the fundamental process of light-matter interaction underlying many methods in extreme ultraviolet and soft x-ray spectroscopy.},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Dynamics of photoemission from surfaces are usually studied at low photon energies (<100 eV). Here, we report on new findings on these dynamics observed at a tungsten surface on the attosecond time scale at photon energies exceeding 100 eV, over a range of almost 50 eV. While photoemission, a fundamental process in quantum mechanics, is often described within a semiclassical three-step model, we find that even at high photon energies only a full quantum treatment in one step predicts the measured attosecond dynamics correctly. On this time scale the intuitive, mechanistic interpretation of the photoelectric effect breaks down. This underlines the necessity to further develop experimental and theoretical tools to be used in improving our understanding of the fundamental process of light-matter interaction underlying many methods in extreme ultraviolet and soft x-ray spectroscopy.
10.
M Nuber, Q Y Tan, D Sandner, J Yin, R Kienberger, C Soci, H Iglev
Accelerated polaron formation in perovskite quantum dots monitored via picosecond infrared spectroscopy Journal Article
In: Journal of Materials Chemistry C, vol. 11, no. 10, pp. 3581-3587, 2023, ISSN: 2050-7526.
@article{nokey,
title = {Accelerated polaron formation in perovskite quantum dots monitored via picosecond infrared spectroscopy},
author = {M Nuber and Q Y Tan and D Sandner and J Yin and R Kienberger and C Soci and H Iglev},
url = {http://dx.doi.org/10.1039/D2TC04519B},
doi = {10.1039/D2TC04519B},
issn = {2050-7526},
year = {2023},
date = {2023-02-06},
journal = {Journal of Materials Chemistry C},
volume = {11},
number = {10},
pages = {3581-3587},
abstract = {The formation and nature of polarons in perovskite quantum dots (QDs) are still unclear. Due to the very limited crystal size and quantum confinement, influences on the polaron stabilization dynamics could be expected. Here, we investigate the coupling of photoexcited charges to vibrational modes in mixed cation lead halide Cs0.2FA0.8PbBr3 QDs via picosecond mid-infrared spectroscopy in comparison to the bulk film. We find additional processes occurring in an infrared activated vibrational (IRAV) mode compared to the ground-state bleaching and screened carrier background signal. Using that mode as a proxy for the charge-molecular bond coupling, we interpret additional time constant as a polaron stabilization time. With the confinement effects present in the QDs, this time shortens from tens of picoseconds in the bulk to only a few picoseconds.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The formation and nature of polarons in perovskite quantum dots (QDs) are still unclear. Due to the very limited crystal size and quantum confinement, influences on the polaron stabilization dynamics could be expected. Here, we investigate the coupling of photoexcited charges to vibrational modes in mixed cation lead halide Cs0.2FA0.8PbBr3 QDs via picosecond mid-infrared spectroscopy in comparison to the bulk film. We find additional processes occurring in an infrared activated vibrational (IRAV) mode compared to the ground-state bleaching and screened carrier background signal. Using that mode as a proxy for the charge-molecular bond coupling, we interpret additional time constant as a polaron stabilization time. With the confinement effects present in the QDs, this time shortens from tens of picoseconds in the bulk to only a few picoseconds.
9.
M Nuber, L V Spanier, S Roth, G N Vayssilov, R Kienberger, P Müller-Buschbaum, H Iglev
In: The Journal of Physical Chemistry Letters, pp. 10418-10423, 2022.
@article{nokey,
title = {Picosecond Charge-Transfer-State Dynamics in Wide Band Gap Polymer\textendashNon-Fullerene Small-Molecule Blend Films Investigated via Transient Infrared Spectroscopy},
author = {M Nuber and L V Spanier and S Roth and G N Vayssilov and R Kienberger and P M\"{u}ller-Buschbaum and H Iglev},
url = {https://doi.org/10.1021/acs.jpclett.2c02864},
doi = {10.1021/acs.jpclett.2c02864},
year = {2022},
date = {2022-11-03},
journal = {The Journal of Physical Chemistry Letters},
pages = {10418-10423},
abstract = {Organic solar cells based on wide band gap polymers and nonfullerene small-molecule acceptors have demonstrated remarkably good device performances. Nevertheless, a thorough understanding of the charge-transfer process in these materials has not been achieved yet. In this study, we use Fano resonance signals caused by the interaction of broad electronic charge carrier absorption and the molecular vibrations of the electron acceptor molecule to monitor the charge-transfer state dynamics. In our time-resolved infrared spectroscopy experiments, we find that in the small-molecule acceptor, they have additional dynamics on the order of a few picoseconds. A change in the solvent used in thin film deposition, leading to different morphologies, influences this time further. We interpret our findings as the dynamics of the charge-transfer state at the interface of the electron donor and the electron- acceptor. The additional mid-infrared transient signal is generated in this state, as both electron and hole polarons can interact with small-molecule acceptor vibrational modes.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Organic solar cells based on wide band gap polymers and nonfullerene small-molecule acceptors have demonstrated remarkably good device performances. Nevertheless, a thorough understanding of the charge-transfer process in these materials has not been achieved yet. In this study, we use Fano resonance signals caused by the interaction of broad electronic charge carrier absorption and the molecular vibrations of the electron acceptor molecule to monitor the charge-transfer state dynamics. In our time-resolved infrared spectroscopy experiments, we find that in the small-molecule acceptor, they have additional dynamics on the order of a few picoseconds. A change in the solvent used in thin film deposition, leading to different morphologies, influences this time further. We interpret our findings as the dynamics of the charge-transfer state at the interface of the electron donor and the electron- acceptor. The additional mid-infrared transient signal is generated in this state, as both electron and hole polarons can interact with small-molecule acceptor vibrational modes.
8.
D Sandner, H Esmaielpour, F Del Giudice, M Nuber, R Kienberger, G Koblmüller, H Iglev
Hot Carrier Dynamics in InAs-AlAsSb Core-Shell Nanowires Journal Article
In: arXiv preprint arXiv:2210.11886, 2022.
@article{nokey,
title = {Hot Carrier Dynamics in InAs-AlAsSb Core-Shell Nanowires},
author = {D Sandner and H Esmaielpour and F Del Giudice and M Nuber and R Kienberger and G Koblm\"{u}ller and H Iglev},
url = {https://arxiv.org/abs/2210.11886},
doi = {https://doi.org/10.48550/arXiv.2210.11886},
year = {2022},
date = {2022-10-25},
journal = {arXiv preprint arXiv:2210.11886},
abstract = {Semiconductor nanowires (NWs) have shown evidence of robust hot carrier effects due to their small dimensions. The relaxation dynamics of hot carriers in these nanostructures, generated by photo-absorption, are of great importance in optoelectronic devices and high efficiency solar cells, such as hot carrier solar cells. Among various III-V semiconductors, indium arsenide (InAs) NWs are promising candidates for their applications in advanced light harvesting devices due to their high photo-absorptivity and high mobility. Here, we investigate the hot carrier dynamics in InAs-AlAsSb core-shell NWs, as well as bare-core InAs NWs, using ultrafast pump-probe spectroscopy with widely tuned pump and probe energies. We have found a lifetime of 2.3 ps for longitudinal optical (LO) phonons and hot electron lifetimes of about 3 ps and 30 ps for carrier-carrier interactions and electron-phonon interactions, respectively. In addition, we have investigated the electronic states in the AlAsSb-shell and found that, despite the large band offset of the core-shell design in the conduction band, excited carriers remain in the shell longer than 100 ps. Our results indicate evidence of plasmon-tailored core-shell NWs for efficient light harvesting devices, which could open potential avenues for improving the efficiency of photovoltaic solar cells.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Semiconductor nanowires (NWs) have shown evidence of robust hot carrier effects due to their small dimensions. The relaxation dynamics of hot carriers in these nanostructures, generated by photo-absorption, are of great importance in optoelectronic devices and high efficiency solar cells, such as hot carrier solar cells. Among various III-V semiconductors, indium arsenide (InAs) NWs are promising candidates for their applications in advanced light harvesting devices due to their high photo-absorptivity and high mobility. Here, we investigate the hot carrier dynamics in InAs-AlAsSb core-shell NWs, as well as bare-core InAs NWs, using ultrafast pump-probe spectroscopy with widely tuned pump and probe energies. We have found a lifetime of 2.3 ps for longitudinal optical (LO) phonons and hot electron lifetimes of about 3 ps and 30 ps for carrier-carrier interactions and electron-phonon interactions, respectively. In addition, we have investigated the electronic states in the AlAsSb-shell and found that, despite the large band offset of the core-shell design in the conduction band, excited carriers remain in the shell longer than 100 ps. Our results indicate evidence of plasmon-tailored core-shell NWs for efficient light harvesting devices, which could open potential avenues for improving the efficiency of photovoltaic solar cells.
7.
F Ristow, K Liang, J Pittrich, J Scheffel, N Fehn, R Kienberger, U Heiz, A Kartouzian, H Iglev
Large-area SHG-CD probe intrinsic chirality in polycrystalline films Journal Article
In: Journal of Materials Chemistry C, vol. 10, no. 35, pp. 12715-12723, 2022, ISSN: 2050-7526.
@article{nokey,
title = {Large-area SHG-CD probe intrinsic chirality in polycrystalline films},
author = {F Ristow and K Liang and J Pittrich and J Scheffel and N Fehn and R Kienberger and U Heiz and A Kartouzian and H Iglev},
url = {http://dx.doi.org/10.1039/D2TC01700H},
doi = {10.1039/D2TC01700H},
issn = {2050-7526},
year = {2022},
date = {2022-08-01},
journal = {Journal of Materials Chemistry C},
volume = {10},
number = {35},
pages = {12715-12723},
abstract = {We used second harmonic generation (SHG) spectroscopy to study the chiroptical properties of R-, S- and racemic (RAC-) 1,1′-bi-2-naphthol (BINOL) films with various thicknesses, incidence angles and degrees of crystallization in the film. The SHG intensity measured at 337 nm increases for thicker films and upon crystallization, while the extracted SHG-circular dichroism (SHG-CD) shows two different regimes depending on the size of the investigated sample area. The data measured at small beam areas, compared to the supramolecular domain size, show strong variation of SHG-CD values depending on the local crystalline structure. In contrast, the anisotropy values measured for beam areas larger than the domain size are almost independent of local sample morphology, film thickness and incidence angle. The SHG-CD values change their sign upon sample flipping or going from R- to S-BINOL. Most interestingly, the observed SHG-CD almost coincides with the value reported for molecular monolayers. Our study reveals that SHG-CD measured with large beam areas can nullify the in-plane anisotropy by averaging over many domains, and thus directly probes intrinsic chirality of the sample. Molecule- and enantiospecific SHG-CD values for BINOL were obtained: ±1.06 for R- and S-BINOL, and 0.01 for racemic BINOL.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We used second harmonic generation (SHG) spectroscopy to study the chiroptical properties of R-, S- and racemic (RAC-) 1,1′-bi-2-naphthol (BINOL) films with various thicknesses, incidence angles and degrees of crystallization in the film. The SHG intensity measured at 337 nm increases for thicker films and upon crystallization, while the extracted SHG-circular dichroism (SHG-CD) shows two different regimes depending on the size of the investigated sample area. The data measured at small beam areas, compared to the supramolecular domain size, show strong variation of SHG-CD values depending on the local crystalline structure. In contrast, the anisotropy values measured for beam areas larger than the domain size are almost independent of local sample morphology, film thickness and incidence angle. The SHG-CD values change their sign upon sample flipping or going from R- to S-BINOL. Most interestingly, the observed SHG-CD almost coincides with the value reported for molecular monolayers. Our study reveals that SHG-CD measured with large beam areas can nullify the in-plane anisotropy by averaging over many domains, and thus directly probes intrinsic chirality of the sample. Molecule- and enantiospecific SHG-CD values for BINOL were obtained: ±1.06 for R- and S-BINOL, and 0.01 for racemic BINOL.
6.
M Nuber, D Sandner, T Neumann, R Kienberger, F Deschler, H Iglev
Bimolecular Generation of Excitonic Luminescence from Dark Photoexcitations in Ruddlesden–Popper Hybrid Metal-Halide Perovskites Journal Article
In: The Journal of Physical Chemistry Letters, vol. 12, no. 42, pp. 10450-10456, 2021.
@article{nokey,
title = {Bimolecular Generation of Excitonic Luminescence from Dark Photoexcitations in Ruddlesden\textendashPopper Hybrid Metal-Halide Perovskites},
author = {M Nuber and D Sandner and T Neumann and R Kienberger and F Deschler and H Iglev},
url = {https://doi.org/10.1021/acs.jpclett.1c03099},
doi = {10.1021/acs.jpclett.1c03099},
year = {2021},
date = {2021-10-21},
journal = {The Journal of Physical Chemistry Letters},
volume = {12},
number = {42},
pages = {10450-10456},
abstract = {The nature of photoexcitations in Ruddlesden\textendashPopper (RP) hybrid metal halide perovskites is still under debate. While the high exciton binding energy in the hundreds of millielectronvolts indicates excitons as the primary photoexcitations, recent reports found evidence for dark, Coulombically screened populations, which form via strong coupling of excitons and the atomic lattice. Here, we use time-resolved mid-infrared spectroscopy to gain insights into the nature and recombination of such dark excited states in (BA)2(MA)n−1PbnI3n+1 (n = 1,2,3) via their intraband electronic absorption. In stark contrast to results in the bulk perovskites, all samples exhibit a broad, unstructured mid-IR photoinduced absorbance with no infrared activated modes, independent of excitonic confinement. Further, the recombination dynamics are dominated by a bimolecular process. In combination with steady-state photoluminescence experiments, we conclude that screened, dark photoexcitations act as a population reservoir in the RP hybrid perovskites, from which nongeminate formation of bright excitons precedes generation of photoluminescence.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The nature of photoexcitations in Ruddlesden–Popper (RP) hybrid metal halide perovskites is still under debate. While the high exciton binding energy in the hundreds of millielectronvolts indicates excitons as the primary photoexcitations, recent reports found evidence for dark, Coulombically screened populations, which form via strong coupling of excitons and the atomic lattice. Here, we use time-resolved mid-infrared spectroscopy to gain insights into the nature and recombination of such dark excited states in (BA)2(MA)n−1PbnI3n+1 (n = 1,2,3) via their intraband electronic absorption. In stark contrast to results in the bulk perovskites, all samples exhibit a broad, unstructured mid-IR photoinduced absorbance with no infrared activated modes, independent of excitonic confinement. Further, the recombination dynamics are dominated by a bimolecular process. In combination with steady-state photoluminescence experiments, we conclude that screened, dark photoexcitations act as a population reservoir in the RP hybrid perovskites, from which nongeminate formation of bright excitons precedes generation of photoluminescence.
5.
M Mittermair, F Martin, M Wörle, D Bloß, A Duensing, R Kienberger, A Hans, H Iglev, A Knie, W Helml
Water jet space charge spectroscopy: Route to direct measurement of electron dynamics for organic systems in their natural environment Journal Article
In: arXiv preprint arXiv:2110.10044, 2021.
@article{nokey,
title = {Water jet space charge spectroscopy: Route to direct measurement of electron dynamics for organic systems in their natural environment},
author = {M Mittermair and F Martin and M W\"{o}rle and D Blo\ss and A Duensing and R Kienberger and A Hans and H Iglev and A Knie and W Helml},
year = {2021},
date = {2021-10-19},
journal = {arXiv preprint arXiv:2110.10044},
abstract = {The toolbox for time-resolved direct measurements of electron dynamics covers a variety of methods. Since the experimental effort is increasing rapidly with achievable time resolution, there is an urge for simple and robust measurement techniques. Within this paper prove of concept experiments and numerical simulations are utilized to investigate the applicability of a new setup for the generation of ultrashort electron pulses in the energy range of 300 eV up to 1.6 keV. The experimental approach combines an in-vacuum liquid microjet and a few-cycle femtosecond laser system, while the threshold for electron impact ionization serves as a gate for the effective electron pulse duration. The experiments prove that electrons in the keV regime are accessible and that the electron spectrum can be easily tuned by laser intensity and focal position alignment with respect to the water jet. Numerical simulations show that a sub-picosecond temporal resolution is achievable.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The toolbox for time-resolved direct measurements of electron dynamics covers a variety of methods. Since the experimental effort is increasing rapidly with achievable time resolution, there is an urge for simple and robust measurement techniques. Within this paper prove of concept experiments and numerical simulations are utilized to investigate the applicability of a new setup for the generation of ultrashort electron pulses in the energy range of 300 eV up to 1.6 keV. The experimental approach combines an in-vacuum liquid microjet and a few-cycle femtosecond laser system, while the threshold for electron impact ionization serves as a gate for the effective electron pulse duration. The experiments prove that electrons in the keV regime are accessible and that the electron spectrum can be easily tuned by laser intensity and focal position alignment with respect to the water jet. Numerical simulations show that a sub-picosecond temporal resolution is achievable.
4.
D Potamianos, M Nuber, A Schletter, M Schnitzenbaumer, M Haimerl, P Scigalla, M Wörle, L I Wagner, R Kienberger, H Iglev
Full Dynamics Description of Mg Phthalocyanine Crystalline and Amorphous Semiconductor Systems Journal Article
In: The Journal of Physical Chemistry C, 2021, ISSN: 1932-7447.
@article{nokey,
title = {Full Dynamics Description of Mg Phthalocyanine Crystalline and Amorphous Semiconductor Systems},
author = {D Potamianos and M Nuber and A Schletter and M Schnitzenbaumer and M Haimerl and P Scigalla and M W\"{o}rle and L I Wagner and R Kienberger and H Iglev},
url = {https://doi.org/10.1021/acs.jpcc.1c04698},
doi = {10.1021/acs.jpcc.1c04698},
issn = {1932-7447},
year = {2021},
date = {2021-08-16},
journal = {The Journal of Physical Chemistry C},
abstract = {Based on visible and mid-infrared transient absorption studies, probing the inter- and intraband dynamics, respectively, of magnesium phthalocyanine (MgPc) organic semiconductors, we were able to develop a model to describe the dynamics and the resulting optical response. We demonstrate how the model could offer insights into the dynamics of more complicated systems such as amorphous MgPc samples obtained by established preparation methods. In particular, we show a clear dimensionality difference of the exciton dissipation mechanism between crystalline and amorphous MgPc, which we resolve in the intraband dynamics, and how this result can also be deduced from the interband dynamics through the implementation of the developed model.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Based on visible and mid-infrared transient absorption studies, probing the inter- and intraband dynamics, respectively, of magnesium phthalocyanine (MgPc) organic semiconductors, we were able to develop a model to describe the dynamics and the resulting optical response. We demonstrate how the model could offer insights into the dynamics of more complicated systems such as amorphous MgPc samples obtained by established preparation methods. In particular, we show a clear dimensionality difference of the exciton dissipation mechanism between crystalline and amorphous MgPc, which we resolve in the intraband dynamics, and how this result can also be deduced from the interband dynamics through the implementation of the developed model.
3.
K Stallhofer, M Nuber, D Cortecchia, A Bruno, R Kienberger, F Deschler, C Soci, H Iglev
Picosecond Charge Localization Dynamics in CH3NH3PbI3 Perovskite Probed by Infrared-Activated Vibrations Journal Article
In: The Journal of Physical Chemistry Letters, pp. 4428-4433, 2021.
@article{,
title = {Picosecond Charge Localization Dynamics in CH3NH3PbI3 Perovskite Probed by Infrared-Activated Vibrations},
author = {K Stallhofer and M Nuber and D Cortecchia and A Bruno and R Kienberger and F Deschler and C Soci and H Iglev},
url = {https://doi.org/10.1021/acs.jpclett.1c00935},
doi = {10.1021/acs.jpclett.1c00935},
year = {2021},
date = {2021-05-05},
journal = {The Journal of Physical Chemistry Letters},
pages = {4428-4433},
abstract = {Hybrid metal halide perovskites exhibit well-defined semiconducting properties and efficient optoelectronic performance considering their soft crystal structure and low-energy lattice motions. The response of such a crystal lattice to light-induced charges is a fundamental question, for which experimental insight into ultrafast time scales is still sought. Here, we use infrared-activated vibrations (IRAV) of the organic components within the hybrid perovskite lattice as a sensitive probe for local structural reorganizations after photoexcitation, with femtosecond resolution. We find that the IRAV signal response shows a delayed rise of about 3 ps and subsequent decay of pronounced monomolecular character, distinguishing it from absorption associated with free carriers. We interpret our results as a two-step carrier localization process. Initially, carriers localize transiently in local energy minima formed by lattice fluctuations. A subpopulation of these can then fall into deeper trapped states over picoseconds, likely due to local reorganization of the organic molecules surrounding the carriers.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hybrid metal halide perovskites exhibit well-defined semiconducting properties and efficient optoelectronic performance considering their soft crystal structure and low-energy lattice motions. The response of such a crystal lattice to light-induced charges is a fundamental question, for which experimental insight into ultrafast time scales is still sought. Here, we use infrared-activated vibrations (IRAV) of the organic components within the hybrid perovskite lattice as a sensitive probe for local structural reorganizations after photoexcitation, with femtosecond resolution. We find that the IRAV signal response shows a delayed rise of about 3 ps and subsequent decay of pronounced monomolecular character, distinguishing it from absorption associated with free carriers. We interpret our results as a two-step carrier localization process. Initially, carriers localize transiently in local energy minima formed by lattice fluctuations. A subpopulation of these can then fall into deeper trapped states over picoseconds, likely due to local reorganization of the organic molecules surrounding the carriers.
2.
M Wörle, A W Holleitner, R Kienberger, H Iglev
Ultrafast hot carrier relaxation in silicon monitored by phase-resolved transient absorption spectroscopy Journal Article
In: arXiv preprint arXiv:2101.01439, 2021.
@article{,
title = {Ultrafast hot carrier relaxation in silicon monitored by phase-resolved transient absorption spectroscopy},
author = {M W\"{o}rle and A W Holleitner and R Kienberger and H Iglev},
year = {2021},
date = {2021-01-05},
journal = {arXiv preprint arXiv:2101.01439},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
1.
H Bi, C A Palma, Y X Gong, K Stallhofer, M Nuber, C Jing, F Meggendorfer, S Z Wen, C Y Yam, R Kienberger, M Elbing, M Mayor, H Iglev, J V Barth, J Reichert
Electron-Phonon Coupling in Current-Driven Single-Molecule Junctions Journal Article
In: Journal of the American Chemical Society, vol. 142, no. 7, pp. 3384-3391, 2020, ISSN: 0002-7863.
@article{,
title = {Electron-Phonon Coupling in Current-Driven Single-Molecule Junctions},
author = {H Bi and C A Palma and Y X Gong and K Stallhofer and M Nuber and C Jing and F Meggendorfer and S Z Wen and C Y Yam and R Kienberger and M Elbing and M Mayor and H Iglev and J V Barth and J Reichert},
url = {\<Go to ISI\>://WOS:000515214000020},
doi = {10.1021/jacs.9b07757},
issn = {0002-7863},
year = {2020},
date = {2020-02-19},
journal = {Journal of the American Chemical Society},
volume = {142},
number = {7},
pages = {3384-3391},
abstract = {Vibrational excitations provoked by coupling effects during charge transport through single molecules are intrinsic energy dissipation phenomena, in close analogy to electron-phonon coupling in solids. One fundamental challenge in molecular electronics is the quantitative determination of charge-vibrational (electron-phonon) coupling for single-molecule junctions. The ability to record electron-phonon coupling phenomena at the single-molecule level is a key prerequisite to fully rationalize and optimize charge-transport efficiencies for specific molecular configurations and currents. Here we exemplarily determine the pertaining coupling characteristics for a current-carrying chemically well-defined molecule by synchronous vibrational and current- voltage spectroscopy. These metal-molecule-metal junction insights are complemented by time-resolved infrared spectroscopy to assess the intramolecular vibrational relaxation dynamics. By measuring and analyzing the steady-state vibrational distribution during transient charge transport in a bis-phenylethynyl-anthracene derivative using anti-Stokes Raman scattering, we find similar to 0.5 vibrational excitations per elementary charge passing through the metal-moleculemetal junction, by means of a rate model ansatz and quantum-chemical calculations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Vibrational excitations provoked by coupling effects during charge transport through single molecules are intrinsic energy dissipation phenomena, in close analogy to electron-phonon coupling in solids. One fundamental challenge in molecular electronics is the quantitative determination of charge-vibrational (electron-phonon) coupling for single-molecule junctions. The ability to record electron-phonon coupling phenomena at the single-molecule level is a key prerequisite to fully rationalize and optimize charge-transport efficiencies for specific molecular configurations and currents. Here we exemplarily determine the pertaining coupling characteristics for a current-carrying chemically well-defined molecule by synchronous vibrational and current- voltage spectroscopy. These metal-molecule-metal junction insights are complemented by time-resolved infrared spectroscopy to assess the intramolecular vibrational relaxation dynamics. By measuring and analyzing the steady-state vibrational distribution during transient charge transport in a bis-phenylethynyl-anthracene derivative using anti-Stokes Raman scattering, we find similar to 0.5 vibrational excitations per elementary charge passing through the metal-moleculemetal junction, by means of a rate model ansatz and quantum-chemical calculations.