Sahu, Satyajit

2024, Dibyajyoti Saikia, Sahu, Satyajit

All inorganic halide perovskites have received tremendous significance in the perovskite solar cells (PSCs) technology. The toxicity in PSCs due to Pb element concerns to the environment, thus replacement of Pb is a prerequisite in the development of PSCs. In this study, we have studied strain-induced structural and electronic properties of lead-free ASnBr3 (A = Cs, Rb, K) perovskites using density functional theory based first principles calculation. The band gap values of these perovskites are varied from 0 to 1.14 eV within the strain range of -4 to 4%.

2024, Chayan Das, Suresh Kumar, Neha V. Dambhare, Mahesh Kumar, Arup K. Rath, Satyajit Sahu

Semiconducting 2D transition metal dichalcogenides (TMDC) became very popular in photodetection due to their high mobility and high rate of generating electron and hole pairs. Over the past decade, MoS2 and WS2 became the most popular TMDC for several applications. On the other hand, due to the complex synthesis process compared to MoS2 and WS2, SnS2 became a less popular 2D material for photodetection. We synthesized vertically aligned SnS2 flakes by a chemical vapor deposition (CVD) process with three temperature zones with controlled argon (Ar) gas flow. Pristine SnS2-based devices are not very suitable for photodetection applications because of their low photo-to-dark current ratio (Iph/Idark), high response time, and low stability. So, they need to be decorated with oppositely doped materials. We decorated pristine SnS2-based devices with rGO nanoparticles, which significantly increased the device’s performance. We found a high responsivity (R) of 1.33 A/W, detectivity (D) of 6.95 × 1011 Jones, Iph/Idark of 102, and a rise time of 0.241 ms (fall time of 1.318 ms) with the rGO decorated SnS2-based device.

2024, Suresh Kumar, Ashok Kumar, Amit Kumar, Atul G. Chakkar, Atanu Betal, Pradeep Kumar, Sahu, Satyajit, Kumar, Mahesh

Hydrogen (H2) is widely used in industrial processes and is one of the well-known choices for storage of renewable energy. H2 detection has become crucial for safety in manufacturing, storage, and transportation due to its strong explosivity. To overcome the issue of explosion, there is a need for highly selective and sensitive H2 sensors that can function at low temperatures. In this research, we have adequately fabricated an unreported van der Waals (vdWs) PdSe2/WS2 heterostructure, which exhibits exceptional properties as a H2 sensor. The formation of these heterostructure devices involves the direct selenization process using chemical vapor deposition (CVD) of Pd films that have been deposited on the substrate of SiO2/Si by DC sputtering, followed by drop casting of WS2 nanoparticles prepared by a hydrothermal method onto device substrates including pre-patterned electrodes. The confirmation of the heterostructure has been done through the utilization of powder X-ray diffraction (XRD), depth-dependent X-ray photoelectron spectroscopy (XPS) and field-emission scanning electron microscopy (FE-SEM) techniques. Also, the average roughness of thin films is decided by Atomic Force Microscopy (AFM). The comprehensive research shows that the PdSe2/WS2 heterostructure-based sensor produces a response that is equivalent to 67.4% towards 50 ppm H2 at 100 °C. The response could be a result of the heterostructure effect and the superior selectivity for H2 gas in contrast to other gases, including NO2, CH4, CO and CO2, suggesting tremendous potential for H2 detection. Significantly, the sensor exhibits fast response and a recovery time of 31.5 s and 136.6 s, respectively. Moreover, the explanation of the improvement in gas sensitivity was suggested by exploiting the energy band positioning of the PdSe2/WS2 heterostructure, along with a detailed study of variations in the surface potential. This study has the potential to provide a road map for the advancement of gas sensors utilizing two-dimensional (2D) vdWs heterostructures, which exhibit superior performance at low temperatures.

2022-03-01, Chetia, Anupam, Bera, Jayanta, Betal, Atanu, Sahu, Satyajit

Photodetectors (PD) are highly useful components in the field of imaging and communication devices. Although the PDs using standard semiconductor materials have numerous benefits, these have certain drawbacks regarding manufacturing costs and integration processes to improve performance. Because of which a niche area towards application in consumer goods and defense is inhibited. This review article discussed the photodetection mechanism, their performance parameter, and the PDs based on low dimensional materials such as zero-dimensional, two dimensional, and their hybrid structures. Owing to the unique and excellent optoelectronic properties of low dimensional materials, and by choosing a facile, improved preparation method, we can achieve high-performance PDs.

2021-01-01, Betal, Atanu, Bera, Jayanta, Sahu, Satyajit

The thermoelectric materials so far discovered have shown thermoelectric behavior at relatively higher temperatures. Low temperature thermoelectric materials are the need of the hour and in this work we have studied the thermoelectric behavior of 2D monolayer of XI2 (X = Sn, Si) at relatively low temperature by using Density Functional Theory (DFT) along with the Boltzmann Transport equation. We have found high thermoelectric figure of merit (ZT) for SnI2 and SiI2 at 600 K. At room temperature the maximum ZT is 0.66 (0.35), 0.78 (0.51) for p-type (n-type) SnI2 and SiI2 respectively and at 600 K it is 0.83 for SiI2. The study of the optical properties of both the materials shows that both of them have indirect band gap with SnI2 having a band gap of 2.06 eV where as SiI2 has a band gap of 1.63 eV. Both the materials have a very high absorption coefficient in the ultraviolet (UV) region hence these materials can be used as high sensitive UV photodetectors. Thus the SnI2 and SiI2 2D monolayers can have potential application in optoelectronic as well as thermoelectric device fabrication.

2023, Dibyajyoti Saikia, Mahfooz Alam, Atanu Betal, Chayan Das, Gandi, Appala Naidu, Sahu, Satyajit

Recently, researchers have focused on developing more stable, Pb-free perovskites with improved processing efficiency and notable light harvesting ability. In this regard, Sn-based (Sn-b) perovskites have gained considerable interest in developing eco-friendly perovskite solar cells (PSCs). However, the oxidation of Sn2+ to Sn4+ deteriorates the performance of Sn-b PSCs. Nevertheless, this issue could be mitigated by doping alkaline earth (AE) metal. Herein, we have studied the significance of AE doping on CsSnX3 (X = Br, I) perovskites using density functional theory based calculations. The structural, electronic, and optical properties of CsAE y Sn1−y X3 (y = 0, 0.25; AE = Be, Mg, Ca, Sr) compounds were systematically investigated to explore potential candidate materials for photovoltaic applications. Formation energy calculations suggested that the synthesis of other AE-doped compounds is energetically favorable except for the Be-doped compounds. The band gaps of the materials were calculated to be in the range of 0.12-1.02 eV using the generalized gradient approximation. Furthermore, the AE doping considerably lowers the exciton binding energy while remarkably enhancing the optical absorption of CsSnX3, which is beneficial for solar cells. However, in the case of Be and Mg doping, an indirect band gap is predicted. Our theoretical findings demonstrate the potential of executing AE-doped perovskites as absorber material in PSCs, which could deliver better performance than pristine CsSnX3 PSCs.

2024, Jai Mishra, Nipun Sharma, Sumit Kumar, Chayan Das, Amit Kumar, Monika Kwoka, Sahu, Satyajit, Kumar, Mahesh

Mercury (Hg2+) sensors play a crucial role in monitoring the quality of drinking water and ensuring that the concentration of Hg2+ ions remains within the permissible limits set by the World Health Organization (WHO). This study introduces a carefully fabricated electrochemical sensor that can accurately detect Hg2+, with high selectivity and sensitivity. The sensor utilizes cyclic voltammetry (CV) to accurately measure Hg2+ concentrations. An advanced composite electrode is fabricated by combining multi-walled carbon nanotubes (MWCNT) and MoS2 on a glassy carbon electrode (GCE) substrate, which functions as the sensing element. The interaction between MWCNT and MoS2 enhances electron transfer kinetics at the electrode interface, leading to faster reactions. These results show a significant 32-times increase in the peak current response for Hg2+ reduction compared to the bare GCE. As a result, the sensor can achieve a low detection limit (LoD) of 2 nM, surpassing the strict safety standards set by the WHO for Hg2+ in water. In addition, the fabricated electrode shows exceptional selectivity towards Hg2+. There are very few changes in the current when different heavy metal ions, such as Pb2+, Co2+, and As3+, are present. In addition, the sensor demonstrates exceptional repeatability, reproducibility and stability, showcasing its great promise for real-world use in monitoring the environment and conducting advanced chemical analysis.

2024, Chayan Das, Suresh Kumar, Neha V. Dambhare, Kumar, Mahesh, Arup K. Rath, Sahu, Satyajit

Semiconducting 2D transition metal dichalcogenides (TMDC) became very popular in photodetection due to their high mobility and high rate of generating electron and hole pairs. Over the past decade, MoS2 and WS2 became the most popular TMDC for several applications. On the other hand, due to the complex synthesis process compared to MoS2 and WS2, SnS2 became a less popular 2D material for photodetection. We synthesized vertically aligned SnS2 flakes by a chemical vapor deposition (CVD) process with three temperature zones with controlled argon (Ar) gas flow. Pristine SnS2-based devices are not very suitable for photodetection applications because of their low photo-to-dark current ratio (Iph/Idark), high response time, and low stability. So, they need to be decorated with oppositely doped materials. We decorated pristine SnS2-based devices with rGO nanoparticles, which significantly increased the device’s performance. We found a high responsivity (R) of 1.33 A/W, detectivity (D) of 6.95 × 1011 Jones, Iph/Idark of 102, and a rise time of 0.241 ms (fall time of 1.318 ms) with the rGO decorated SnS2-based device.

2024, Mubashir Mushtaq Ganaie, Amit Kumar, Amit K. Shringi, Sahu, Satyajit, Michael Saliba, Kumar, Mahesh

In conventional designs, sensory systems are segregated from memory and computing units. The conversion and transmission of data from analog sensing domains to digital storage result in inefficient power utilization and increased latency. Here, a multifunctional memristor capable of detecting gamma radiation while also serving as a data storage device and an artificial synapse is reported. Large-scale integration of oxide-based memristors for artificial neural networks faces major challenges due to the sneak-path current issue in crossbar arrays. Consequently, material combinations and fabrication variables significantly shape nanoscale processes, which are essential in determining resistive switching properties and functionalities. Resistive switching in AlFeO3 is studied using different electrode materials (silver (Ag), gold (Au), chromium (Cr), fluorine-doped tin oxide, and silicon), embedding metal (Ag, Au) nanocrystals to engineer a class of tunable memories capable of functioning as selector, memory, artificial synapse, and dosimeter. Techniques like electrode engineering, nanocrystal seeding, and temperature-dependent thin film deposition are employed to tune resistive and threshold switching functionalities. Accessing different functionalities requires changing the electrode materials or changing the synthesis conditions of the AlFeO3 resistive switching layer and are not interconvertible in the same device simultaneously. The devices emulate critical neural functions and demonstrate interconversion dynamics between short-term and long-term plasticity.

2024, Shubham Bawa, Anil Kumar, Gaurav Kumar Nim, Jayanta Bera, Samaresh Ghosh, Sahu, Satyajit, Prasenjit Kar, Anasuya Bandyopadhyay

The tunable molecular scaffold of organic moieties in metallopolymers generates variation in their properties, but what could be the minimal change that can produce variation in the properties of these macromolecules is still untouched. This research has meticulously explored the trivial change in the molecular scaffold of the ligand capable of making a mammoth difference in the nonvolatile memory and coordination pattern in two metallopolymers. The significance of this research lies in the fact that it demonstrates how a slight change in the organic building block can significantly alter the memristive and fluorescence properties of iron(ii) metallopolymers, opening up new possibilities for their design and synthesis. Two novel positional isomeric ligands and their corresponding iron(ii)-polymers were synthesized and thoroughly characterized using NMR, XRD, ATR-IR, FESEM, AFM and other techniques. Bright orange solid and solution state fluorescence was observed both in the solid and solution states for ligand L2 (3,3′-bis((E)-(pyridin-3-ylimino)methyl)-[1,1′-biphenyl]-4,4′-diol), while ligand L1 (3,3′-bis((E)-(pyridin-2-ylimino)methyl)-[1,1′-biphenyl]-4,4′-diol) showed blue fluorescence in the solution state only. A robust memristive property for Fe(ii)-L1-poly with a high current ON/OFF ratio of 104, remarkable random access behaviour, and a long retention time greater than 35 000 seconds was observed while its counterpart was entirely silent. Both polymers showed solution-state electrochromism. These synthesised metallopolymers also showed good specific capacitance in the range of 50-60 F g−1 with a remarkable retention of 98% of the initial value even after 5000 charge-discharge cycles. The AFM and FESEM micrographs revealed the formation of long polymer nano-rods, which correlates with the NMR, ATR-IR, and XRD results. The difference in the properties of polymers generated by such a slight change in the organic building block forces different coordination patterns of these two ligands around the same central metal ion, and this is also evident in all the characterization methods.