Sudipta Seth
@hofkenslab.com
Postdoctoral researcher at the Molecular Imaging and Photonics, Department of Chemistry, KU Leuven
Prof. Johan Hofkens
RESEARCH, TEACHING, or OTHER INTERESTS
Spectroscopy, Physical and Theoretical Chemistry, Electronic, Optical and Magnetic Materials, Materials Chemistry
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
N. V. S. Praneeth, Syed Akhil, Amitrajit Mukherjee, Sudipta Seth, Saumyakanti Khatua, and Nimai Mishra
Wiley
AbstractConventional amine‐capped perovskite nanocrystals (A‐PNCs) often show microscopic fluctuation (blinking) of photoluminescence (PL) between bright and near‐background (dark) states. The transient dark phases spanning milliseconds (ms) to several seconds timescale typically owe to the non‐radiative (NR) fate of charge carriers in crystal defect states, limiting the PNC's efficiency in optoelectronics. A PL study of a novel trioctylphosphine (TOP) capped rhombic cuboctahedron‐shaped amine‐free (AF) PNC is presented, demonstrating their fascinating nonblinking nature. While oleylamine‐capped hexahedron A‐PNCs as a reference system show long dark states, their population is completely suppressed in ≈90% of AF‐PNCs with random large‐amplitude PL fluctuations several times above the background. The PL trajectories of AF‐PNCs primarily comprise constant power spectral densities (PSDs) which are unprecedented and deviate from power‐law distribution as observed for A‐PNCs and most of the other blinking nanocrystals. Such signature of PSDs and frame‐by‐frame intensity jump analysis indicate a fast (<<ms) timescale charge‐carrier dynamics governing the PL emission of AF‐PNCs, likely involving short‐lived metastable states. Besides, long‐term stability and suppressed dark phases in ≈70% AF‐PNCs even 90 days after the synthesis is noteworthy. Altogether the study provides exceptional optical characteristics of photostable amine‐free PNCs which would be attractive to exploit in commercial display applications.
Juanzi Shi, Igor Ryabov, Sudipta Seth, Pavel A. Frantsuzov, Safi Rafie-Zinedine, Andreas Walther, Maria E. Messing, Xiangang Wu, Wengao Lu, Haizheng Zhong,et al.
American Chemical Society (ACS)
Alexander Kiligaridis, Pavel A. Frantsuzov, Aymen Yangui, Sudipta Seth, Jun Li, Qingzhi An, Yana Vaynzof, and Ivan G. Scheblykin
Springer Science and Business Media LLC
AbstractMetal halide perovskites are an important class of emerging semiconductors. Their charge carrier dynamics is poorly understood due to limited knowledge of defect physics and charge carrier recombination mechanisms. Nevertheless, classical ABC and Shockley-Read-Hall (SRH) models are ubiquitously applied to perovskites without considering their validity. Herein, an advanced technique mapping photoluminescence quantum yield (PLQY) as a function of both the excitation pulse energy and repetition frequency is developed and employed to examine the validity of these models. While ABC and SRH fail to explain the charge dynamics in a broad range of conditions, the addition of Auger recombination and trapping to the SRH model enables a quantitative fitting of PLQY maps and low-power PL decay kinetics, and extracting trap concentrations and efficacies. However, PL kinetics at high power are too fast and cannot be explained. The proposed PLQY mapping technique is ideal for a comprehensive testing of theories and applicable to any semiconductor.
Sudipta Seth, Eduard A. Podshivaylov, Jun Li, Marina Gerhard, Alexander Kiligaridis, Pavel A. Frantsuzov, and Ivan G. Scheblykin
Wiley
AbstractPhotoluminescence (PL) blinking is a common phenomenon in nanostructured semiconductors associated with charge trapping and defect dynamics. PL blinking kinetics exhibit very broadly distributed timescales. The traditionally employed analysis of probability distribution of ON and OFF events suffers from ambiguities in their determination in complex PL traces making its suitability questionable. Here, the statistically correct power spectral density (PSD) estimation method applicable for fluctuations of any complexity is employed. PSDs of the blinking traces of submicrometer MAPbI3 crystals at high frequencies follow power law with excitation power density dependent parameters. However, at frequencies less than 0.3 Hz, the majority of the PSDs saturate revealing the presence of a maximal characteristic timescale of blinking in the range of 0.5–10 s independently of the excitation power density. Super‐resolution optical microscopy shows the characteristic timescale to be an inherent material property independent of polycrystallinity. Thus, for the first time the maximum timescale of the multiscale blinking behavior of nanoparticles is observed demonstrating that the power law statistics are not universal for semiconductors. It is proposed that the viscoelasticity of metal‐halide perovskites can limit the maximum timescale for the PL fluctuations by limiting the memory of preceded deformations/re‐arrangements of the crystal lattice.
Navendu Mondal, Apurba De, Sudipta Seth, Tasnim Ahmed, Somnath Das, Sumanta Paul, Rajesh Kumar Gautam, and Anunay Samanta
American Chemical Society (ACS)
The recent emergence of metal halide perovskites as triplet sensitizers has generated new possibilities in optoelectronics, the exploitation of which requires an understanding of the characteristic...
Naupada Preeyanka, Himani Dey, Sudipta Seth, Abdur Rahaman, and Moloy Sarkar
Royal Society of Chemistry (RSC)
Highly efficient energy transfer from a water soluble quantum dot to organic J-aggregates in an inorganic–organic nanohybrid associate.
Somnath Banerjee, Naupada Preeyanka, Himani Dey, Sudipta Seth, Abdur Rahaman, and Moloy Sarkar
American Chemical Society (ACS)
With an aim to understand the interaction between the inorganic and organic components in inorganic–organic hybrid nanostructured materials, we have designed and developed an inorganic–organic nano...
Sudipta Seth, Tasnim Ahmed, Apurba De, and Anunay Samanta
American Chemical Society (ACS)
Defects have always been an integral part of semiconductor crystals, controlling their optical and electronic properties. Even though growing popularity of the CsPbX3 (X = Cl, Br, I, and their mixt...
Anil Kanwat, Won‐Chul Choi, Sudipta Seth, and Jin Jang
Wiley
AbstractHere, we demonstrate a simple method to improve photoluminescence and electroluminescent properties of MAPbBr3 perovskite thin films by monovalent Cs cation doping and treatment with UV light. It is known that the intermediate species of lead halides, which limits the photoluminescence quantum yield (PLQY) of perovskite thin films, are formed due to the presence of an organic polar solvent. In such cases, coalescence of nanocrystals is unavoidable when the thin‐films are thermally annealed to remove the intermediate phases and solvent residues. We find that PbBr2(DMSO)x complexes can effectively tune the morphology, grain boundary, PLQY, and non‐radiative loss of perovskite thin films under UV light irradiation. Upon UV exposure, highly uniform MA0.87Cs0.13PbBr3 ultra‐thin (45 nm) films with a full surface coverage of neatly packed nanocrystallites are obtained. When these films are integrated into electroluminescent devices, a current efficiency (CE) of 18.71 Cd/A and an external quantum efficiency (EQE) of 5.63% are observed for green perovskite‐based light emitting diodes (PeLEDs). These values of CE and EQE are respectively thirty‐four and forty‐three times higher than those achieved in pure MAPbBr3 based devices.
Aman Kumar Agrawal, Prabhat Kumar Sahu, Sudipta Seth, and Moloy Sarkar
American Chemical Society (ACS)
With an objective to understand the interaction between the inorganic and organic components of inorganic–organic hybrid nanomaterials, we have fabricated and studied the photonic properties of a nanocomposite system consisting of a silver-capped gold nanoparticle as the inorganic component and the J-aggregate of cyanine-based dye (S2165) as the organic component. The present hybrid construct has been fabricated by adopting electrostatically driven self-assembly of organic cyanine dye and inorganic silver-capped gold (AgCAu) nanoparticle. In contrast to the previously developed hybrid systems where fluorescent inorganic semiconductor quantum dots are integrated with J-aggregates, the formation of the hybrid system in the present work is carried out by exploiting the fluorescent AgCAu nanoparticle and the J-aggregate of the cyanine dye. The hybrid system has been characterized by spectroscopic and microscopic techniques. Steady-state and time-resolved fluorescence measurements have been performed on this h...
K. N. Krishnakanth, Sudipta Seth, Anunay Samanta, and S. Venugopal Rao
Royal Society of Chemistry (RSC)
Lead halide perovskite nanocrystals have recently demonstrated promising nonlinear optical properties such as strong two-photon absorption, three-photon absorption, four-photon absorption and their respective cross-sections.
Tasnim Ahmed, Sudipta Seth, and Anunay Samanta
American Chemical Society (ACS)
Exploration of the full potential of the perovskite nanocrystals (NCs) for different applications requires a thorough understanding of the pathways of recombination of the photo-generated charge carriers and associated dynamics. In this work, we have tracked the recombination routes of the charge carriers by probing photoluminescence (PL) intermittency of the immobilized and freely diffusing single CsPbBr3 NCs employing a time-tagged-time-resolved method. The immobilized single CsPbBr3 NCs show a complex PL time-trace, a careful analysis of which reveals nonradiative band-edge recombination through trap states, radiative and nonradiative trion recombination and trapping of the hot carriers contribute to the blinking behavior of any given NC. A drastically suppressed PL blinking observed for the NCs treated with a tetrafluoroborate salt indicates elimination of most of the undesired recombination processes. Fluorescence correlation spectroscopy (FCS) study on the freely diffusing single NCs shows that enhanced PL and suppressed blinking of the treated particles is the outcome of an increase in per-particle brightness, not due to any increase in the number of particles undergoing "off"-"on" transition in the observation volume. The mechanistic details obtained from this study on the orgin of blinking in CsPbBr3 NCs provide deep insight into the radiative and nonradiative charge carrier recombination pathways in these important materials and this knowledge is expected to be useful for better design and development of bright photoluminescent samples of this class for optoelectronic applications.
Sudipta Seth, Tasnim Ahmed, and Anunay Samanta
American Chemical Society (ACS)
To obtain an in-depth understanding of the dynamics and mechanism of carrier recombination in CsPbBr3 nanocrystals (NCs), we have investigated the photoluminescence (PL) of this material at the single-particle level using the time-tagged-time-resolved method. The study reveals two distinct types of PL fluctuations of the NCs, which are assigned to flickering and blinking. The flickering is found to be due to excess surface trap on the NCs, and the flickering single particles are transformed into blinking ones with significant enhancement of PL intensity and stability on postsynthetic surface treatment. Intensity-correlated lifetime analysis of the PL time trace reveals both trap-mediated nonradiative band-edge carrier recombination and positive trion recombination in single NCs. Dynamical and statistical analysis suggests a diffusive nature of the trap states to be responsible for the PL intermittency of the system. These findings throw light on the nature of the trap states, reveal the manifestation of these trap states in PL fluctuation, and provide an effective way to control the dynamics of CsPbBr3 NCs.
Subhasis Roy, Naupada Preeyanka, Debashis Majhi, Sudipta Seth, and Moloy Sarkar
American Chemical Society (ACS)
Despite several studies, convincing explanation for the fluorescence of carbon dots (CDs) and its excitation wavelength dependence behavior has not yet emerged. It may be noted that direct structure–property correlation can be misleading based on solely transmission electron microscopy micrographs as it does not fully reveal the possibility of heterogeneous nature of the samples in a sense that it does not fully reveal the possibility of having both carbonaceous nanoparticles as well as small organic molecular-based systems. The present work is undertaken specifically to address this issue. A detailed spectroscopic investigation comprising steady-state absorption, emission, time-resolved fluorescence, and fluorescence correlation spectroscopy (FCS) studies has been carried out on CDs, synthesized from two different sources. Similar investigations have also been carried out on the systems such as aromatic and aliphatic ionic liquids (ILs), which are known to be fluorescent in their neat conditions. Interes...
Tasnim Ahmed, Sudipta Seth, and Anunay Samanta
American Chemical Society (ACS)
Katturi Naga Krishnakanth, Sudipta Seth, Anunay Samanta, and Soma Venugopal Rao
The Optical Society
We report the broadband nonlinear optical (NLO) properties of CsPbBr3 perovskite films achieved from colloidal nanocrystals prepared following a room temperature and open atmosphere anti-solvent precipitation method. The NLO studies were performed on the films of nanocubes (NCs) and nanorods (NRs) using the Z-scan technique with 1 kHz femtosecond pulses at 600, 700, and 800 nm. Large two-photon absorption cross sections (∼105 GM) were retrieved by fitting the open-aperture Z-scan data. Strong third-order NLO susceptibility (∼10-10 esu) was observed in these films. At higher peak intensities a switching of sign (in both NCs and NRs) in the real and imaginary parts of the NLO susceptibility was observed from the studies on these CsPbBr3 nanocrystals. The obtained NLO coefficients clearly suggest that these materials are promising for ultrafast photonic applications.
Sudipta Seth and Anunay Samanta
American Chemical Society (ACS)
Zero-dimensional (0-D) perovskites and perovskite-related materials are an emerging class of optoelectronic materials exhibiting strong excitonic properties and, quite often, high photoluminescence (PL) in the solid state. Here we highlight two different classes of 0-D perovskites with contrasting structural and optical properties, focusing mainly on the less explored but rapidly growing bulk quantum materials termed as 0-D perovskite-related materials (0-D PRMs), whose PL properties are quite intriguing and a topic of recent debate. We attempt to present here a comprehensive picture to rationalize the contrasting properties of the 0-D PRMs and provide an understanding of the mechanism of exciton dynamics and PL of this class of materials. We hope that exciting PL and tunable composition of these systems will help design of new materials with versatile optical properties suited for practical applications.
Debashis Majhi, Sudipta Seth, and Moloy Sarkar
Royal Society of Chemistry (RSC)
Two imidazolium-based dicationic ionic liquids and one monocationic ionic liquid were investigated to understand their intermolecular interactions, structure and dynamics.
Sudipta Seth and Anunay Samanta
American Chemical Society (ACS)
Quantum-confined perovskites are a new class of promising materials in optoelectronic applications. In this context, a zero-dimensional perovskite-related substance, Cs4PbBr6, having high exciton binding energy can be an important candidate, but its photoluminescence (PL) is a topic of recent debate. Herein, we report an ambient condition controlled synthesis of Cs4PbBr6 microdisks of different shapes and dimensions which exhibit fairly strong green PL (quantum yield up to 38%, band gap ∼2.43 eV) in the solid state. Using confocal fluorescence microscopy imaging of the single particles, we show that the fluorescence of Cs4PbBr6 microdisks is inherent to these particles. Fluorescence intensity and lifetime imaging of the microdisks reveals significant spatial heterogeneity with a bright central area and somewhat dimmer edges. This intensity and lifetime distribution is attributed to enhanced trap-mediated nonradiative deactivation at the edges compared to the central region of the microdisks. Our results, which unambiguously establish the PL of these Cs4PbBr6 and suggest its possible origin, brighten the potential of these materials in photon-emitting applications.
Sudipta Seth and Anunay Samanta
Springer Science and Business Media LLC
AbstractA facile and highly reproducible room temperature, open atmosphere synthesis of cesium lead halide perovskite nanocrystals of six different morphologies is reported just by varying the solvent, ligand and reaction time. Sequential evolution of the quantum dots, nanoplates and nanobars in one medium and nanocubes, nanorods and nanowires in another medium is demonstrated. These perovskite nanoparticles are shown to be of excellent crystalline quality with high fluorescence quantum yield. A mechanism of the formation of nanoparticles of different shapes and sizes is proposed. Considering the key role of morphology in nanotechnology, this simple method of fabrication of a wide range of high quality nanocrystals of different shapes and sizes of all-inorganic lead halide perovskites, whose potential is already demonstrated in light emitting and photovoltaic applications, is likely to help widening the scope and utility of these materials in optoelectronic devices.
Prabhat Kumar Sahu, Raju Nanda, Sudipta Seth, Arindam Ghosh, and Moloy Sarkar
Elsevier BV
Sudipta Seth, Navendu Mondal, Satyajit Patra, and Anunay Samanta
American Chemical Society (ACS)
Study of the emission behavior of all-inorganic perovskite nanocrystals CsPbBr3 and CsPbBr2I as a function of the excitation power employing fluorescence correlation spectroscopy and conventional techniques reveals fluorescence blinking in the microsecond time scale and photoinduced emission enhancement. The observation provides insight into the radiative and nonradiative deactivation pathways of these promising substances. Because both blinking and photoactivation processes are intimately linked to the charge separation efficiency and dynamics of the nanocrystals, these key findings are likely to be helpful in realizing the true potential of these substances in photovoltaic and optoelectronic applications.
Debashis Majhi, Prabhat Kumar Sahu, Sudipta Seth, and Moloy Sarkar
Royal Society of Chemistry (RSC)
Structurally similar but chemically distinguishable solutes provide idea about intermolecular interactions in ionic liquids.
Satyajit Patra, Sudipta Seth, and Anunay Samanta
Wiley
AbstractThe effect of one and two monolayers of ZnS shells on the photostability of CdTe quantum dots (QDs) in aqueous and nonaqueous media has been studied by monitoring the fluorescence behavior of the QDs under ensemble and single‐molecule conditions. ZnS capping of the CdTe QDs leads to significant enhancement of the fluorescence brightness of these QDs. Considerable enhancement of the photostability of the shell‐protected QDs, including the suppression of photoactivation, is also observed. Fluorescence correlation spectroscopy measurements reveal an increase in the number of particles undergoing reversible fluorescent on–off transitions in the volume under observation with increasing excitation power; this effect is found to be more pronounced in the case of core‐only QDs than for core–shell QDs.
Sivalingam Soumya, Sudipta Seth, Sneha Paul, and Anunay Samanta
Wiley
AbstractThe microenvironments of a leucine‐based organogel are probed by monitoring the fluorescence behavior of coumarin 153 (C153) and 4‐aminophthalimide (AP). The steady‐state data reveals distinctly different locations of the two molecules in the gel. Whereas AP resides close to the hydroxyl moieties of the gelator and engages in hydrogen‐bonding interactions, C153 is found in bulk‐toluene‐like regions. In contrast to C153, AP exhibits excitation‐wavelength‐dependent emission, indicating that the environments of the hydrogen‐bonded AP molecules are not all identical. A two‐component fluorescence decay of AP in gel, unlike C153, supports this model. A time‐resolved fluorescence anisotropy study of the rotational motion of the molecules also reveals the strong association of only AP with the gelator. That AP influences the critical gelation concentration implies its direct involvement in the gel‐formation process. The results highlight the importance of guest–gelator interactions in gels containing guest molecules.