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Ł. Kłopotowski

Polish Academy of Sciences

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P. Wojnar

Polish Academy of Sciences

T. Wójtowicz

Institute of Physics

J. Kossut

Polish Academy of Sciences

K. Fronc

Polish Academy of Sciences

G. Karczewski

Institute of Physics

Paulina Płochocka

Centre National de la Recherche Scientifique

T. Kazimierczuk

University of Warsaw

M. Szymura

Institute of Physics

L. Viña

Universidad Autónoma de Madrid

Alessandro Surrente

Wrocław University of Science and Technology

Cooperative Institutions

Polish Academy of Sciences

Institute of Physics

University of Warsaw

Centre National de la Recherche Scientifique

Czech Academy of Sciences, Institute of Physics

Université Grenoble Alpes

Laboratoire National des Champs Magnétiques Intenses

Sorbonne Université

Institute of High Pressure Physics

Wojewódzki Inspektorat Ochrony Środowiska w Warszawie

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Influence of oversized cations on electronic dimensionality of d-MAPbI₃ crystals

Journal of Materials Chemistry C (2020)

Mateusz Dyksik Michał Baranowski Antonin Leblanc Alessandro Surrente Miriam Karpińska

Here we show the hybrid nature of lead-deficient perovskites reflected by the surprising coexistence of 3D-like and lower dimensional domains.

10.1039/d0tc01566k

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Citations (2)

Intervalley scattering of excitons and trions in monolayer WSe$_{2}$ under strong excitation

arXiv (Cornell University) (2015)

Anatolie Mitioglu Ł. Kłopotowski D. K. Maude G. Deligeorgis S. Anghel

Monolayer transition metal dichalcogenides offer the possibility of optical control of the valley degree of freedom. In order to asses the potential of these materials in applications, detailed knowledge of the valley dynamics is essential. In this work, we apply low temperature time-resolved photoluminescence (PL) measurements to investigate exciton valley relaxation dynamics and, in particular, its behavior under strong excitation. At the lowest excitation powers the inter valley scattering time is $\simeq 50$ ps, but shortens by more than a factor of two at the highest powers. We attribute this acceleration to either heating of the exciton system or the presence of a dense exciton gas, which could influence the exciton valley properties. Furthermore, we analyze the PL dynamics of excitons and trions. We find that the PL decays for all peaks are bi-exponential and approximately independent of the excitation power. We attribute the short decay to radiative recombination and escape to a reservoir of dark states. The long decay is ascribed to a transfer of excitons back from the reservoir. For the first time, we evaluate the exciton PL decay time of $\simeq$ 10 ps. The latter process is valley-conserving and occurs on a timescale of $\simeq$ 50 ps.

Exponential decay

10.48550/arxiv.1507.00496

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Citations (1)

Non equilibrium anisotropic excitons in atomically thin ReS ₂

2D Materials (2018)

J. Urban Michał Baranowski Agnieszka Kuc Ł. Kłopotowski Alessandro Surrente

We present a systematic investigation of the electronic properties of bulk and few layer ReS$_2$ van der Waals crystals using low temperature optical spectroscopy. Weak photoluminescence emission is observed from two non-degenerate band edge excitonic transitions separated by $\sim$ 20 meV. The comparable emission intensity of both excitonic transitions is incompatible with a fully thermalized (Boltzmann) distribution of excitons, indicating the hot nature of the emission. While DFT calculations predict bilayer ReS$_2$ to have a direct fundamental band gap, our optical data suggests that the fundamental gap is indirect in all cases.

10.1088/2053-1583/aae9b9

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Stark spectroscopy of CdTe and CdMnTe quantum dots embedded in n-i-p diodes

Journal of Applied Physics (2014)

Ł. Kłopotowski K. Fronc P. Wojnar M. Wiater T. Wójtowicz

We investigate charging effects in CdTe and Cd1−xMnxTe quantum dots embedded in n-i-p diodes. The tunneling of holes out of the dots at reverse bias and hole injection at forward bias control the dot charge state and allow for its electric field tuning. Furthermore, we analyze the Stark shifts of the photoluminescence transitions and evaluate the effect of the electric field on the binding of the observed excitonic complexes. We find that the binding can be strengthened or weakened depending on the zero-field alignment of the electron and hole wavefunctions.

Cadmium telluride photovoltaics

Quantum-confined Stark effect

10.1063/1.4878978

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Magnetic polaron formation and exciton spin relaxation in single Cd1−xMnxTe quantum dots

Physical Review B (2011)

Ł. Kłopotowski Łukasz Cywiński P. Wojnar V. Voliotis K. Fronc

We study the formation dynamics of a spontaneous ferromagnetic order in single self-assembled CdMnTe quantum dots. By measuring time-resolved photoluminescence, we determine the formation times for QDs with Mn ion contents x varying from 0.01 to 0.2. At low x these times are orders of magnitude longer than exciton spin relaxation times evaluated from the decay of photoluminescence circular polarization. This allows us to conclude that the direction of the spontaneous magnetization is determined by a momentary Mn spin fluctuation rather than resulting from an optical orientation. At higher x, the formation times are of the same order of magnitude as found in previous studies on higher dimensional systems. We also find that the exciton spin relaxation accelerates with increasing Mn concentration.

10.1103/physrevb.83.081306

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Citations (44)

Charge storage in self-assembled CdTe quantum dots

Journal of Physics Conference Series (2010)

Ł. Kłopotowski M. Goryca P. Kossacki A. Kudelski Oliver Krebs

We demonstrate storage of photoexcited electrons in a layer of self assembled CdTe quantum dots embedded in a field-effect structure. We study the storage efficiency with respect to the duration of the photoexcitation pulse. The electrons persist in the quantum dots for as long as 9 milliseconds.

Photoexcitation

Cadmium telluride photovoltaics

10.1088/1742-6596/210/1/012007

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Citations (2)

Tunneling of spin polarized excitons in CdTe based asymmetric double quantum well structure

Solid State Communications (2001)

Ł. Kłopotowski M. Nawrocki J. A. Gaj Sebastian Maćkowski E. Janik

Cadmium telluride photovoltaics

Biexciton

10.1016/s0038-1098(01)00230-7

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Citations (11)

Synthesis and magnetooptic characterization of Cu-doped ZnO/MgO and ZnO/oleic acid core/shell nanoparticles

RSC Advances (2016)

J. Mikulski Bożena Sikora K. Fronc P. Aleshkevych S. Kret

The effect of Cu ion doping on the photoluminescence (PL) and magnetic behavior of ZnO/MgO and ZnO/oleic acid core/shell nanoparticles is investigated.

Characterization

10.1039/c6ra01453d

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Citations (8)

Exciton recombination dynamics in single ZnO tetrapods

AIP conference proceedings (2013)

Lígia C. Fernandes-Silva M. D. Martı́n H. P. van der Meulen Ł. Kłopotowski J. M. Calleja

We present the optical properties of individual ZnO tetrapods as a function of excitation power and temperature by time-integrated and time-resolved spectroscopy. At 10K, we identify the different excitonic transitions by both their characteristic energy and their excitation power dependence. When we increase the tetrapod temperature we observe that the emission intensity decrease and occur a red shift of the emission energies. Our time-resolved studies confirm the predominance of the radiative recombination at low temperatures (< 45 K). Increasing the temperature opens up the non-radiative channels, which are evidenced by a much faster decay time.

10.1063/1.4848293

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Interlayer excitons in MoSe₂/2D perovskite hybrid heterostructures – the interplay between charge and energy transfer

Nanoscale (2022)

Miriam Karpińska J. Jasiński Roman Kempt Jonas D. Ziegler Harry C. Sansom

van der Waals crystals have opened a new and exciting chapter in heterostructure research, removing the lattice matching constraint characteristics of epitaxial semiconductors. They provide unprecedented flexibility for heterostructure design. Combining two-dimensional (2D) perovskites with other 2D materials, in particular transition metal dichalcogenides (TMDs), has recently emerged as an intriguing way to design hybrid opto-electronic devices. However, the excitation transfer mechanism between the layers (charge or energy transfer) remains to be elucidated. Here, we investigate PEA2PbI4/MoSe2 and (BA)2PbI4/MoSe2 heterostructures by combining optical spectroscopy and density functional theory (DFT) calculations. We show that band alignment facilitates charge transfer. Namely, holes are transferred from TMDs to 2D perovskites, while the electron transfer is blocked, resulting in the formation of interlayer excitons. Moreover, we show that the energy transfer mechanism can be turned on by an appropriate alignment of the excitonic states, providing a rule of thumb for the deterministic control of the excitation transfer mechanism in TMD/2D-perovskite heterostructures.

10.1039/d2nr00877g

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Citations (16)