Browsing by Author "Pardeep K. Jha"

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Anisotropic photoconduction in ultrathin CuO: A nonreciprocal system?
(American Institute of Physics Inc., 2022) Ashish K. Ranjan; Priyanka A. Jha; Pardeep K. Jha; Prabhakar Singh
With the recent global surge in the research on perovskite halides, CuO is one of the binary oxides, which gets attention as a hole transport material. In centrosymmetric CuO, parity-time (P T) violation leads to photoconduction. The P Tsymmetry can be preserved if the system were non-reciprocal. Thus, in the current work, we fabricated an ultra-thin film of CuO using pulsed laser deposition and observed anisotropic photoconduction. The semiconductor parameters estimated from the photoresponse suggest that the relative value of free charge carrier density is neither altered significantly with thickness reduction nor with light exposure as it is quite low (∼10 - 7) suggesting high trap (deep) density. Further, anisotropic photocurrent in the absence of an electric field suggests the alteration in electromagnetic potential due to the existence of self-biasing and structural asymmetry. The application of Gauge field variance on 2D photonic metasurface reveals the non-chiral nature. It is suggesting T-symmetry breaking, and, therefore, the possibility of the photonic Aharonov-Bohm effect is expected in CuO thin films. © 2022 Author(s).
Bandgap and electrochemical engineering for disordered LaFeO3
(American Institute of Physics Inc., 2022) Uma Sharma; U.K. Kailash Veerappan; Pardeep K. Jha; Priyanka A. Jha; Prabhakar Singh
Being a charge transfer Mott insulator with low metal-insulator temperature, disordered LaFeO 3 (as an air electrode) is a potential material for electrochemical engineering. High electronic conductivity and inexpensive catalytic activity are the prime requisites for electrode materials. Here, we systematically substituted hole (Sr) at La-site and electron (Ti) at Fe-site. Our objective is here twofold, first to get material with improved catalytic behavior and to understand the role of bandgap engineering. All the investigated samples are oxygen-rich and show orthorhombic(Pbnm) phase at 300 K. The prominent cation vacancies are closely associated with the self-trapping of carriers. These trapping centers may be detrimental if they shift toward conduction band minima. However, this energy shift can be controlled with proper selection of substitution but require intricate understanding. At 300 K, we observe higher conductivity with band shrinkage for hole substitution, i.e., La 0.5Sr 0.5FeO 3 (LSF). A field dependent electrical study reveals trap free conduction for the hole substituted sample while undoped and compensated show ohmic conduction. Our results suggest that there is a correlation between band tuning and corrosion resistance. Dynamic numerical simulation, where interfacial electrochemical behavior up to 4000 s is studied, suggests that LSF has the least surface charge degradation. Experimentally, LSF proves to be a robust and efficient electrode due to chronopotentiometry stability with a potential of 2 V (vs Ag/AgCl) at a higher current of 150 mA/cm 2 in neutral media. Further, this study provides concomitant charge dynamics for these samples and the foster mechanism to get better air electrodes. © 2022 Author(s).
Bandgap engineering in TiO2/rGO 1D photonic metasurfaces as broadband solar absorber
(American Institute of Physics Inc., 2022) Yash K. Saurabh; Priyanka A. Jha; Pawan K. Dubey; Pardeep K. Jha; Prabhakar Singh
Inability to use full solar energy, especially near infrared radiation (NIR: 780-1400 nm), is one of the major limitations for solar energy harvesting due to the narrow bandgap (electronic as well as photonic). In this work, we designed the 1D photonic metasurfaces of TiO 2 with reduced graphene oxide (rGO) in an attempt to obtain broader absorption bandwidth in NIR. Further, to realize this experimentally, graphene oxide reduced TiO 2 nanocomposites are synthesized using the hydrothermal method to form a quantum well. The composites are observed in the anatase phase of TiO 2 with graphitic reflection, and microstructural studies that indicate the conversion of TiO 2 nanoparticles into nanotubes with reduced graphene oxide intercalation forming a kind of self-assembled metasurfaces. UV-vis absorption studies indicate a significant reduction in bandgap energy; typically, the indirect bandgap reduces near to zero. The experimental and numerical simulation results suggest phonon scattering dominated free carrier absorption in NIR in the TiO 2/rGO metasurface leading to wide broadband absorption (700-10 000 nm). © 2022 Author(s).
Bandgap tuning for transition metal oxides via PEGylation
(Institute of Physics, 2025) Priyanka A. Jha; Jay N. Mishra; Gargi Yadav; Harinder Kumar Tanti; Ashish K. Ranjan; Pardeep K. Jha; Prabhakar Singh
Bandgap engineering is controlled manipulation of the bandgap of materials/meta-materials to achieve desired properties. The electrical and optical properties of materials are significantly affected by bandgap tuning; therefore, bandgap engineering is a powerful technique for designing electronic and optoelectronic devices. Compositional engineering, strain engineering, and nanoscience and technology are the three major fields associated with bandgap engineering. Any unique combination of this engineering can provide novel strategies to produce novel band-structured devices. In this method article, we have demonstrated how solvation energy can alter the bandgap energy, a fact that is generally ignored due to misconceptions about quantum/size confinement. Here, we prepare nanostructured transition metal oxides (Co3O4, CuO, and ZnO) with polyethylene glycol (PEG), and the method is termed PEGylation. We investigate the influence of PEGylation on the structural, electrochemical, and electronic nature of these oxides. It is observed that the bandgap tunability (7.33%) is maximum for ZnO. Our study suggests that band alteration is significantly correlated with the change in lattice parameters; however, it is orientation dependent as the correlation coefficient reduces to 0.85 from 1 for the change in lattice parameter b along the y-axis compared to the other two lattice parameters. Similarly, band alteration is also known to have some correlation with the electrochemical potential, but is surprisingly almost independent of size confinement. © 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.
Catalyzing hydrogen production: Exploring plasmonic effects in self-assembled CuO/Cu2O thin films via pulsed laser deposition
(American Institute of Physics, 2024) Ashish K. Ranjan; Pardeep K. Jha; Priyanka A. Jha; Prabhakar Singh
Plasmonic catalysis triggers the dissociation of H 2 or adsorbed O 2 (sluggish processes) under continuous wave excitation via plasmon decay. This is coupled to interband or intraband excitation of d-band or sp-band, respectively, to levels above fermi level of metals. Here, we have studied the plasmonic and photocatalytic behavior in an environment friendly medium with AM 1.5 G sunlight of CuO/ Cu 2 O thin films fabricated by pulsed laser deposition technique in vacuum with varying thickness. We have achieved ∼ 0.59 kmol h − 1 g − 1 H 2 production in the CuO/ Cu 2 O film with a thickness of ∼ 27 nm. The role of plasmons with metal-dielectric and semiconductor-semiconductor interfaces is conducted through both experimental and theoretical approaches. The results suggest that the impact of plasmonic catalysis/synthesis is subject to the dimension, composition, and band alignment of two interface materials. © 2024 Author(s).
Compositional degradation with Br content in Cesium lead halide CsPbBrxI3-x
(Academic Press Inc., 2022) Manish Kumar; Vani Pawar; Pardeep K. Jha; Priyanka A. Jha; Prabhakar Singh
The inorganic cesium lead halide CsPbX3 (where X = I, Br, Cl) are reported to possess good stability than that of organic-inorganic hybrid halides. CsPbI3 is reported to have four phases: perovskite black phase (cubic (α), tetragonal (β), orthorhombic(γ)) and non-perovskite yellow orthorhombic (δ). With band gap of ∼ 1.73eV, CsPbI3-α is most suitable phase among all-inorganic lead halide Perovskites. However, in ambient atmosphere (almost instantly) the perovskite black phase convert into non-perovskite yellow orthorhombic phase. At the same time CsPbBr3 remains in the orthorhombic phase at room temperature. Thus, in the present investigation, compositional variation of Br in Cesium lead iodide CsPbBrxI3-x (x = 0.0 to 3.0 at the step of 0.5) samples synthesized by cold sintering technique is studied. The XRD patterns showed the orthorhombic phase for CsPbBr3. Further, CsPbBrxI3-x (x ≤ 1.0) have shown double phase corresponding to CsPbI3 (Pnma) + PbI2 ( R3¯m). However, the compound with 1.5 ≤ x < 3.0 showed the presence of various phases with and without oxygen including the CsPbBr3 (orthorhombic, Pnma) phase which has also been confirmed through UV–visible spectroscopy, impedance and Schottky anomaly. This compositional failure is also suggested by deviation from Vegards law showing volumetric expansion. The role of oxygen vacancy has been probed for the compositional failure for 1.5 ≤ x < 3.0 using XPS characterization and Raman spectroscopy. © 2022 Elsevier Inc.
Electrical conductivity study of A-site non-stoichiometric Na0.5+xBi0.5-xTiO3-δ
(American Institute of Physics Inc., 2020) Pragati Singh; Priyanka A. Jha; Raghvendra Pandey; Pardeep K. Jha; Prabhakar Singh
In the present work effect of A-site non-stoichiometry on the bulk conductivity of sodium bismuth titanate ceramic is studied. Dense ceramic samples of Na0.5+xBi0.5-xTiO3-δ (x = -0.02, 0.00 and 0.02) were prepared using solid-state reaction route at the sintering temperature of 1150 °C. The XRD results show the formation of rhombohedral phase with R3c symmetry. The electrical studies suggest increase in conductivity with the change in stoichiometry. This increase in the conductivity is associated with the increase in the oxygen vacancies, lattice distortion and defects with the change in stoichiometry. © 2020 Author(s).
Electrolytes for electrochemical energy storage supercapacitors
(Bentham Science Publishers, 2024) Priyanka A. Jha; Pardeep K. Jha; Prabhakar Singh
In this chapter, the types of electrolytes and the alteration in capacitance with pore size, their power density, and energy density along with the interaction of electrolytes with current collectors are discussed. The electrolytes' electrochemical stability broadly estimates the working cell voltage provided that the electrodes are stable under operating cell voltage. The electrolytes are divided into various categories such as liquid electrolyte, solid-state, and redox-active electrolyte. The liquid electrolytes are further categorized into aqueous and non-aqueous electrolytes. The critical performance parameters such as stability, lifetime, operating temperature, operating voltage, etc. are believed to be affected by electrolytes. Moreover, the electrolytes are believed to interact with the current collectors, additives, binders, separators, and electrode material to affect the practical performance of supercapacitors. However, the capacitance of the electrolyte depends upon the ion size and the matching between the electrode pore size and electrolyte ion size. The power density and energy density depend upon the potential window, ionic conductivity, and electrochemical stability along with concentration, respectively. Further, the ionelectrode interaction is supposed to affect the cycle life and power density as well. The thermal stability of electrolytes depends upon their boiling points, freezing points, and salt solubility and the equivalent series resistance depends upon ion conductivity, mobility, and viscosity. © 2024 Bentham Science Publishers. All rights reserved.
Hysteresis and pyroelectric behaviour at isomorphic transition in green CsSnI3
(Institute of Physics, 2025) Prem C. Bharti; Priyanka A. Jha; Pardeep K. Jha; Prabhakar Singh
Lead-free perovskite halide CsSnI3 has emerged as a promising material for optoelectronic applications due to its direct bandgap (1.3-1.4 eV), high charge carrier mobility, and strong visible-spectrum absorption. Among its polymorphs, the green phase, with a favorable bandgap of ∼1.24 eV, demonstrates enhanced structural stability and resistance to phase degradation under ambient conditions. In this study, we investigate the green polymorph of CsSnI3 and observe pyroelectric behavior, indicative of ferroelectric-like properties despite its globally centrosymmetric ( P a 3 ― ) cubic structure. Utilizing Piezo-force microscopy, dielectric measurements, impedance spectroscopy, and Raman spectroscopy, we identified local non-centrosymmetry influencing hysteresis and conduction properties. Impedance spectroscopy further reveals the interaction of grains and grain boundaries under a low AC electric field, both before and after light exposure and poling. A reduction in relaxation time with increasing temperature in poled samples is observed, while the combined effects of light exposure and poling result in an increased relaxation time. Our results indicate that local non-centrosymmetry plays a critical role in influencing hysteresis and conduction behavior. These findings highlight the importance of phase transitions and vibrational mode dynamics in optimizing the performance of CsSnI3-based devices, paving the way for their broader application in advanced optoelectronic technologies. © 2025 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.
Hysteric photo-conduction and negative differential resistance in cesium lead bromide
(American Institute of Physics, 2020) Manish Kumar; Priyanka A. Jha; Pardeep K. Jha; Prabhakar Singh
For the perovskite halides, current voltage hysteresis is the biggest puzzle to be solved before industrialization in spite of promising features for future photo-voltaic applications. All the possible causes, from the classical (viz., morphology, defects, slow transient capacitance, etc.) to quantum (viz., spin-orbit interaction) ones, are investigated. However, its origin is still under debate, as possibilities showed some ambiguity on the science known until now. In the present work, we have studied the time dependent photo-conduction behavior of CsPbBr 3 in continuous illumination of AM 1.5 G Sun light for 3 h. We observed a negative differential resistance for a forward scanned current-voltage curve in AM 1.5 G Sun light. Our investigations suggest that the photo-current voltage hysteresis is primarily affected by the thermionic-field emission, which slows down the drift velocity of hot charge carriers with field applications. This study will further lead the scientific community to investigate whether this slowdown in drift velocity is related to the Gunn effect or the Rashba effect. © 2020 Author(s)
La0.5Sr0.5Fe0.5Ti0.5O3 as a Bifunctional Catalyst for H2/O2 Fuel Cells: Towards Enhanced Stability and Electroactivity
(Institute of Physics, 2024) Uma Sharma; Pardeep K. Jha; Priyanka A. Jha; Prabhakar Singh
To address the rising demand for H2 for fuel cells, hydrogen is produced through water splitting (electrochemically/photoelectrochemically).Although perovskite-structured materials show promise for the oxygen reduction reaction (ORR), their effectiveness in the oxygen evolution reaction (OER) poses a challenge. Consequently, there’s a growing demand for bifunctional catalysts exhibiting high electroactivity across a broad pH range. One potential candidate for exploration as a negative electrode in batteries and fuel cells is LaFeO3. With co-substitution of Sr and Ti, La0.5Sr0.5Fe0.5Ti0.5O3 (LSFT) is formed and explored as an air electrode. In this study, we systematically assess LSFT as a bifunctional catalyst across a broad pH spectrum of electrolytic solutions. LSFT displays increased current densities in both the OER and hydrogen evolution reaction (HER) domains, alongside improved stability, notably in neutral conditions. Our investigation incorporates Density Functional Theory (DFT) simulations to determine surface binding energies and construct a Pourbaix diagram. The results underscore the robustness of LSFT as a perovskite-based bifunctional catalyst, achieving a cycle stability exceeding 600 cycles and a chronopotentiometric stability of 1500 h with a stable potential of ∼2 V at the current density of 150 mA/cm2 in the neutral environment. © 2024 The Electrochemical Society (“ECS”). Published on behalf of ECS by IOP Publishing Limited.
Metal-Organic Frameworks (MOFs) based nanomaterials for supercapacitor applications
(Bentham Science Publishers, 2024) Pardeep K. Jha; Priyanka A. Jha; Prabhakar Singh
In the last two decades, nanomaterials with enhanced active sites and better surface kinetics as compared to their bulk counterpart, have been significantly studied for supercapacitor electrode materials. Contemporarily, Metal-organic frameworks (MOFs) by virtue of versatile structure, charge conduction, high porosity, and redoxactive functionality have also emerged as the most potential materials for nextgeneration energy storage technologies. Despite these excellent features, the bulk phase inorganic-MOFs have some chemical and physical limitations that hinder cell performance and thus novel materials are required. Recently, MOFs-based nanomaterials(nMOF) got due attention leading to the discovery of a variety of properties not observed or relevant in bulk systems, such as well-defined 3D structures, permanent porosity, and accelerated adsorption/desorption kinetics. That's why nMOFs are considered an emerging class of modular nanomaterials. However, understanding of nMOFs is still in its infancy, film uniformity along with the unstable structure in a highly corrosive electrolyte is still a bottleneck problem. In this chapter, the recent developments of pristine MOF and MOF-derived porous nanocomposites for the nextgeneration supercapacitor applications will be discussed. © 2024 Bentham Science Publishers. All rights reserved.
Observation of grey cesium tin bromide with unusual phase transition
(Institute of Physics, 2023) Swarnima Singh; Manish Kumar; Pardeep K. Jha; Priyanka A. Jha; Prabhakar Singh
A new grey colour polymorph of CsSnBr3 with non-cubic phase at 295(±1) K is observed. Contrary to black and yellow polymorphs, it seems that not only the β-α transition at 292 K shifted to 304 K but also the new β 3-phase with second-order phase transition (β 2-β 3) can be seen in this new grey polymorph. The structural refinement shows the monoclinic phase with holohedry for β 3-CsSnBr3 against the group-subgroup theory. However, the parameters and are suggesting pseudo-tetragonality for β 3-CsSnBr3 Copyright © 2023 EPLA.
Photoconduction in CuO
(Elsevier Ltd, 2020) Ashish K. Ranjan; Priyanka A. Jha; Pardeep K. Jha; Prabhakar Singh
With the global surge in the research on perovskite halides as cost effective alternative Silicon solar cells, it is necessary to find the replacement of very expensive hole transport materials (HTM). Copper oxide (CuO) is one of the inorganic binary compound and much cheaper than the organic HTMs. In this work, light absorption behaviour and photoconductivity of CuO are examined. The band gap and Urbach energy is estimated using UV-visible absorbance spectrum. The photo-conduction study of the CuO is carried in 1.5AM-G solar light. © 2019 Elsevier Ltd.