MSc. Chemistry from IIT Madras, 2009
PhD from IISc Bangalore, 2015
RESEARCH, TEACHING, or OTHER INTERESTS
Chemistry, Physical and Theoretical Chemistry, Spectroscopy, Energy
27
Scopus Publications
799
Scholar Citations
16
Scholar h-index
17
Scholar i10-index
Scopus Publications
Study of Positive Ageing Effect in Halide Perovskite Quantum Dots Prepared via Novel Alendronic Acid-Based Surface-Passivating Ligand Bharti Kumari, Joydeep Dhar Chemnanomat, 2026 Caesium lead bromide (CsPbBr 3 ) perovskite quantum dots (QDs) are one of the promising materials for the fabrication of green light‐emitting diodes (LEDs) for their near‐unity photoluminescence quantum yield (PLQY) with narrow emission and high brightness. However, its ionic nature makes it susceptible to degradation from moisture, heat and light. Various surface‐passivating ligands were attempted, but with limited success in rendering long‐term stability. Here, we have developed a novel bisphosphonate ligand, alendronate (ALEN), by alkylating with hexyl chains of acidic protons of alendronic acid, which is otherwise sparingly soluble in common organic solvents. The ligand was characterised by spectroscopic techniques such as NMR, FT‐IR, and mass spectroscopies. The CsPbBr 3 QDs prepared with ALEN‐oleylamine ligand combination showed narrow particle‐size distribution as determined by high‐resolution transmission electron microscopy and dynamic light scattering measurements. The photostability of the QDs in solution and thin film was analysed by photoluminescence spectroscopy, revealing an interesting phenomenon called positive ageing effect, in which the PLQY of QD dispersion gradually increased by 140% from its initial value of 7 to 16.94% after two and a half months of storage. The defect passivation through multidentate binding sites of ALEN is the most plausible reason for such behaviour in ALEN‐stabilised CsPbBr 3 QDs.
Studying the Effect of Mn2+ Doping on Structural and Photophysical Properties of Morpholinium Lead Bromide Perovskite Vishal Singh, Joydeep Dhar Chempluschem, 2025 Organic–inorganic lead halide perovskite is under intense focus on developing different optoelectronic devices because of its exceptional optical and electrical properties and ease of processing. However, the Pb 2+ toxicity and the luminescence instability of these classes of semiconductors require continuous development of newer luminescent variants. Herein, Mn 2+ is used as a dopant in luminescent morpholinium lead bromide perovskite, (C 4 H 10 NO)PbBr 3 , to substitute Pb 2+ with Mn 2+ with varied doping percentage to develop two different analogs of Mn 2+ ‐doped (C 4 H 10 NO)PbBr 3 with varied optical properties. The incorporation of the dopant ion is investigated using various characterization techniques like inductively coupled plasma‐optical emission spectroscopy, single‐crystal and powder X‐ray diffraction, infrared, and electron paramagnetic resonance spectroscopies. The photophysical properties are characterized by absorption and emission spectroscopies. With the increase in Mn 2+ ‐dopant amount, the emission maxima showed a blueshift with respect to the pristine sample and exhibited an enhanced (about 40%) photoluminescence quantum yield. Finally, the possibility of utilizing these semiconductors for practical applications is conducted by studying the structural and photophysical properties after embedding them into an optically transparent polymer, polymethyl methacrylate.
Positron annihilation studies of methylammonium lead bromide perovskite Sudipta Moshat, Partha Pratim Ray, Sayantan Sil, Joydeep Dhar, Dirtha Sanyal Physica Scripta, 2023 Methylammonium lead halide-based perovskite has shown excellent optoelectronic properties. But their performances and stability are critically affected by the ionic defects present in the crystal lattice. In this article, we have investigated the presence of ionic vacancy mediated defects formation in ball mill ground methylammonium lead bromide (MAPbBr3) which has applications in tandem solar cell, light emitting diodes and laser devices. The evaluation of those point defects with temperature was analysed by employing the positron annihilation spectroscopic (PAS) studies. The phase transition from tetragonal to cubic phases around 260 K was exactly correlated with the temperature-dependent ‘S parameter’ determination from PAS analysis and with dc conductivity measurement. From coincidence Doppler broadening (CDB) spectroscopy significant proportion of defects arising from lead vacancy was observed whose magnitude reduces from the low-temperature tetragonal phase to higher temperature cubic phases.
Investigating the effect of applied bias on methylammonium lead iodide perovskite by electrical and positron annihilation spectroscopic studies Sayantan Sil, Sudipta Moshat, Partha Pratim Ray, Joydeep Dhar, Dirtha Sanyal Journal of Physics D Applied Physics, 2021 The formation of point defects in the crystal lattice of organic–inorganic hybrid perovskites is detrimental to the long-term stability of the perovskite-based solar cell. The observed hysteresis in organolead halide perovskite solar cell during the photocurrent measurement is believed to be the consequence of such defect sites. In the present work, we are reporting the formation of reversible and/or irreversible lattice defects in methylammonium lead iodide perovskite depending on the magnitude of bias voltage studied by electrical measurements and positron annihilation spectroscopy (PAS). Current vs voltage ( I – V ) measurements support the formation of p/n junction at the metal/semiconductor interfaces, suggesting the defects-driven ion migration under the applied bias. In-situ PAS has elucidated the nature of vacancy sites formed due to the application of bias voltage. In the lower biased voltage (<1 V), the formation of lattice defects is reversible, while beyond a threshold voltage of 1.2 V, the defects become permanent as observed by the PAS.
Study of Positive Ageing Effect in Halide Perovskite Quantum Dots Prepared via Novel Alendronic Acid‐Based Surface‐Passivating Ligand B Kumari, J Dhar ChemNanoMat 12 (4), e202500667 , 2026 2026
Role of positional isomerism in A-site organic cation: structural variation driven photophysical and ferroelectric responses in centrosymmetric layered perovskites V Singh, P Moar, D Sanyal, S Barua, J Dhar Journal of Materials Chemistry C , 2026 2026 Citations: 1
Studying the Effect of Mn 2+ Doping on Structural and Photophysical Properties of Morpholinium Lead Bromide Perovskite V Singh, J Dhar ChemPlusChem 90 (10), e202500241 , 2025 2025 Citations: 3
Zn (II) based fluorescent metal-organic framework as a'turn-off'sensor for Al3+ and Fe3+ ions in aqueous solution: Synthesis, DFT calculations and Hirshfeld surface analysis A De, V Singh, J Dhar, S Mishra Journal of Molecular Structure 1329, 141426 , 2025 2025 Citations: 12
Investigating the effect of lead substitution on the optical, electrical, and photoresponse properties of Quasi-2D double perovskites V Singh, M Das, K Mondal, S Barua, D Sanyal, PP Ray, J Dhar Journal of Physics and Chemistry of Solids 192, 112082 , 2024 2024 Citations: 4
Positron annihilation spectroscopic studies of ferromagnetic methylammonium lead iodide perovskite S Moshat, J Dhar, S Sil, D Sanyal Journal of Materials Science 59 (9), 3919-3929 , 2024 2024 Citations: 1
Positron annihilation studies of methylammonium lead bromide perovskite S Moshat, PP Ray, S Sil, J Dhar, D Sanyal Physica Scripta 98 (3), 035822 , 2023 2023 Citations: 4
Investigating the effect of applied bias on methylammonium lead iodide perovskite by electrical and positron annihilation spectroscopic studies S Sil, S Moshat, PP Ray, J Dhar, D Sanyal Journal of Physics D: Applied Physics 54 (46), 465502 , 2021 2021 Citations: 5
Defect induced room temperature ferromagnetism in methylammonium lead iodide perovskite S Sil, H Luitel, J Dhar, M Chakrabarti, PP Ray, B Bandyopadhyay, ... Physics Letters A 384 (14), 126278 , 2020 2020 Citations: 30
NMR study of defect-induced magnetism in methylammonium lead iodide perovskite B Bandyopadhyay, H Luitel, S Sil, J Dhar, M Chakrabarti, P Nath, PP Ray, ... Physical Review B 101 (9), 094417 , 2020 2020 Citations: 24
Analysis of interfaces in Bornite (Cu5FeS4) fabricated Schottky diode using impedance spectroscopy method and its photosensitive behavior S Sil, A Dey, J Datta, M Das, R Jana, S Halder, J Dhar, D Sanyal, PP Ray Materials Research Bulletin 106, 337–345 , 2018 2018 Citations: 64
Bias voltage-dependent impedance spectroscopy analysis of hydrothermally synthesized ZnS nanoparticles A Dey, J Dhar, S Sil, R Jana, PP Ray Journal of Materials Engineering and Performance 27 (6), 2727-2733 , 2018 2018 Citations: 21
Lattice‐defect‐induced piezo response in methylammonium‐lead‐iodide perovskite based nanogenerator J Dhar, S Sil, NA Hoque, A Dey, S Das, PP Ray, D Sanyal ChemistrySelect 3 (19), 5304-5312 , 2018 2018 Citations: 35
Gaussian Distribution of Inhomogeneous Barrier Height of Al/ZnS/ITO Schottky Barrier Diodes A Dey, R Jana, J Dhar, P Das, PP Ray Materials Today: Proceedings 5 (3), 9958–9964 , 2018 2018 Citations: 19
Positron annihilation spectroscopic investigation on the origin of temperature-dependent electrical response in methylammonium lead iodide perovskite J Dhar, S Sil, A Dey, PP Ray, D Sanyal The Journal of Physical Chemistry Letters 8 (8), 1745-1751 , 2017 2017 Citations: 25
Investigation of ion-mediated charge transport in methylammonium lead iodide perovskite J Dhar, S Sil, A Dey, D Sanyal, PP Ray The Journal of Physical Chemistry C 121 (10), 5515-5522 , 2017 2017 Citations: 27
Is the chemical strategy for imbuing “polyene” character in diketopyrrolopyrrole-based chromophores sufficient for singlet fission? T Mukhopadhyay, AJ Musser, B Puttaraju, J Dhar, RH Friend, S Patil The Journal of Physical Chemistry Letters 8 (5), 984-991 , 2017 2017 Citations: 39
Trends in molecular design strategies for ambient stable n-channel organic field effect transistors J Dhar, U Salzner, S Patil Journal of Materials Chemistry C 5 (30), 7404-7430 , 2017 2017 Citations: 72
Development of large area nanostructured silicon-hydrogen alloy material with improved stability for solar cell application by argon dilution method A Dey, M Das, J Datta, R Jana, J Dhar, S Sil, D Biswas, C Banerjee, ... Electronic Materials Letters 12 (4), 456-461 , 2016 2016 Citations: 1
Effect of chalcogens on electronic and photophysical properties of vinylene-based diketopyrrolopyrrole copolymers J Dhar, T Mukhopadhay, N Yaacobi-Gross, TD Anthopoulos, U Salzner, ... The Journal of Physical Chemistry B 119 (34), 11307-11316 , 2015 2015 Citations: 35
MOST CITED SCHOLAR PUBLICATIONS
Photophysical, electrochemical and solid state properties of diketopyrrolopyrrole based molecular materials: importance of the donor group J Dhar, N Venkatramaiah, S Patil Journal of Materials Chemistry C 2 (17), 3457-3466 , 2014 2014 Citations: 143
Self-assembly and catalytic activity of metal nanoparticles immobilized in polymer membrane prepared via layer-by-layer approach J Dhar, S Patil ACS applied materials & interfaces 4 (3), 1803-1812 , 2012 2012 Citations: 83
Herringbone to cofacial solid state packing via H-bonding in diketopyrrolopyrrole (DPP) based molecular crystals: influence on charge transport J Dhar, DP Karothu, S Patil Chemical Communications 51 (1), 97-100 , 2015 2015 Citations: 74
Trends in molecular design strategies for ambient stable n-channel organic field effect transistors J Dhar, U Salzner, S Patil Journal of Materials Chemistry C 5 (30), 7404-7430 , 2017 2017 Citations: 72
Analysis of interfaces in Bornite (Cu5FeS4) fabricated Schottky diode using impedance spectroscopy method and its photosensitive behavior S Sil, A Dey, J Datta, M Das, R Jana, S Halder, J Dhar, D Sanyal, PP Ray Materials Research Bulletin 106, 337–345 , 2018 2018 Citations: 64
Is the chemical strategy for imbuing “polyene” character in diketopyrrolopyrrole-based chromophores sufficient for singlet fission? T Mukhopadhyay, AJ Musser, B Puttaraju, J Dhar, RH Friend, S Patil The Journal of Physical Chemistry Letters 8 (5), 984-991 , 2017 2017 Citations: 39
Multilayer single-component thin films and microcapsules via covalent bonded layer-by-layer self-assembly U Manna, J Dhar, R Nayak, S Patil Chemical communications 46 (13), 2250-2252 , 2010 2010 Citations: 39
Lattice‐defect‐induced piezo response in methylammonium‐lead‐iodide perovskite based nanogenerator J Dhar, S Sil, NA Hoque, A Dey, S Das, PP Ray, D Sanyal ChemistrySelect 3 (19), 5304-5312 , 2018 2018 Citations: 35
Effect of chalcogens on electronic and photophysical properties of vinylene-based diketopyrrolopyrrole copolymers J Dhar, T Mukhopadhay, N Yaacobi-Gross, TD Anthopoulos, U Salzner, ... The Journal of Physical Chemistry B 119 (34), 11307-11316 , 2015 2015 Citations: 35
Defect induced room temperature ferromagnetism in methylammonium lead iodide perovskite S Sil, H Luitel, J Dhar, M Chakrabarti, PP Ray, B Bandyopadhyay, ... Physics Letters A 384 (14), 126278 , 2020 2020 Citations: 30
Investigation of ion-mediated charge transport in methylammonium lead iodide perovskite J Dhar, S Sil, A Dey, D Sanyal, PP Ray The Journal of Physical Chemistry C 121 (10), 5515-5522 , 2017 2017 Citations: 27
Positron annihilation spectroscopic investigation on the origin of temperature-dependent electrical response in methylammonium lead iodide perovskite J Dhar, S Sil, A Dey, PP Ray, D Sanyal The Journal of Physical Chemistry Letters 8 (8), 1745-1751 , 2017 2017 Citations: 25
NMR study of defect-induced magnetism in methylammonium lead iodide perovskite B Bandyopadhyay, H Luitel, S Sil, J Dhar, M Chakrabarti, P Nath, PP Ray, ... Physical Review B 101 (9), 094417 , 2020 2020 Citations: 24
Modulation of electronic and self-assembly properties of a donor–acceptor–donor-based molecular materials via atomistic approach J Dhar, K Swathi, DP Karothu, KS Narayan, S Patil ACS Applied Materials & Interfaces 7 (1), 670-681 , 2015 2015 Citations: 24
Bias voltage-dependent impedance spectroscopy analysis of hydrothermally synthesized ZnS nanoparticles A Dey, J Dhar, S Sil, R Jana, PP Ray Journal of Materials Engineering and Performance 27 (6), 2727-2733 , 2018 2018 Citations: 21
Gaussian Distribution of Inhomogeneous Barrier Height of Al/ZnS/ITO Schottky Barrier Diodes A Dey, R Jana, J Dhar, P Das, PP Ray Materials Today: Proceedings 5 (3), 9958–9964 , 2018 2018 Citations: 19
Zn (II) based fluorescent metal-organic framework as a'turn-off'sensor for Al3+ and Fe3+ ions in aqueous solution: Synthesis, DFT calculations and Hirshfeld surface analysis A De, V Singh, J Dhar, S Mishra Journal of Molecular Structure 1329, 141426 , 2025 2025 Citations: 12
Selenium in Diketopyrrolopyrrole‐based Polymers: Influence on Electronic Properties and Charge Carrier Mobilities J Dhar, C Kanimozhi, N Yaccobi‐Gross, TD Anthopoulos, U Salzner, ... Israel Journal of Chemistry 54 (5‐6), 817-827 , 2014 2014 Citations: 9
Investigating the effect of applied bias on methylammonium lead iodide perovskite by electrical and positron annihilation spectroscopic studies S Sil, S Moshat, PP Ray, J Dhar, D Sanyal Journal of Physics D: Applied Physics 54 (46), 465502 , 2021 2021 Citations: 5
Correlation between Optical Properties and Nanomorphology of Fluoranthene-Based Conjugated Copolymer J Dhar, S Kumar, S Patil The Journal of Physical Chemistry C 118 (27), 15079-15085 , 2014 2014 Citations: 5