Condensed Matter Physics, Renewable Energy, Sustainability and the Environment, Surfaces, Coatings and Films, Instrumentation
31
Scopus Publications
467
Scholar Citations
12
Scholar h-index
13
Scholar i10-index
Scopus Publications
Negative Ion Implantation Enabled Controlled Oxygen Doping in Iron Pyrite Thin Films Rudra Narayan Chakraborty, Dipta Suryya Mahanta, Kshetrimayum Devarani Devi, Kasilingam Senthilkumar Small Methods, 2026 Iron pyrite (FeS 2 ) is a promising material for next‐generation photovoltaic and optoelectronic applications. However, the origin of p ‐type conductivity in thin films, unlike the n ‐type behavior of bulk FeS 2 , remains unknown and is often attributed to unintentional impurity incorporation, particularly oxygen. This study explores the role of oxygen in tuning the electrical and optical properties of FeS 2 thin films. Phase‐pure FeS 2 thin film is deposited on glass substrates via single‐step co‐sputtering using FeS 2 and S 8 targets at 430°C substrate temperature. The resulting films exhibit p ‐type conductivity with a carrier concentration and mobility of 4.18 × 10 19 cm −3 and 5.06 cm 2 V −1 s −1 respectively. Controlled oxygen incorporation is achieved through negative ion implantation at fluences ranging from 9 × 10 14 to 1 × 10 16 ions cm −2 . X‐ray photoelectron spectroscopy and time of flight secondary ion mass spectrometry confirm successful oxygen doping, with oxygen atoms preferentially occupying sulfur vacancies for higher doses. This incorporation enhances p ‐type conductivity and induces direct bandgap widening up to 1.48 eV. The results demonstrate a pathway to fabricate FeS 2 thin films with high hole concentration and offer a strategy for optimizing the optoelectronic properties for advanced semiconductor applications.
Correlation between microstructural changes and phonon shifts in O−-implanted FeS2 thin films Rudra Narayan Chakraborty, Dipta Suryya Mahanta, Kasilingam Senthilkumar Applied Physics Letters, 2025 This work systematically studies microstructural modifications in FeS2 thin films induced by low-energy oxygen implantation at different fluences. Crystallite size was determined from x-ray diffraction (XRD), while phonon shifts in the Ag Raman vibrational mode were analyzed for all samples. A clear correlation was established between Raman shift, crystallite size, and ion fluence. This approach highlights Raman scattering as a rapid, nondestructive, and complementary alternative to XRD, with significant implications for in situ monitoring of implantation processes. The results provide a robust foundation for linking implantation parameters to structural evolution and phonon behavior of ion-implanted FeS2 thin films.
Machine Learning-Driven Optimization of CuAl1–xFexS2-based Solar Cells with Oxygen-Implanted FeS2Thin Films as the Hole Transport Layer Rudra Narayan Chakraborty, Dipta Suryya Mahanta, Kasilingam Senthilkumar ACS Applied Energy Materials, 2025 Incorporating a hole transport layer (HTL) in a solar cell provides a promising approach to enhance charge extraction and suppress recombination; however, identifying a compatible HTL with a given absorber material remains challenging. This study investigates oxygen-implanted FeS 2 thin films as HTLs in CuAl 1– x Fe x S 2 -based solar cells using a machine learning-assisted framework. A total of 187,200 device simulations were carried out in the SILVACO ATLAS simulator by systematically varying absorber and HTL parameters. Random Forest regression coupled with SHAP analysis identified the absorber bandgap as the most influential factor, with an optimal value of 1.63 eV, corresponding to 41% Fe-substitution in CuAlS 2 . Among the evaluated device structures, the device incorporating oxygen-implanted FeS 2 with a dose of 9 × 10 14 ions cm –2 as HTLs achieved the highest power conversion efficiency of 14.77%, along with an open-circuit voltage of 0.92 V, due to reduced interfacial recombination losses.
Interplay of Polymorphism in FeS2Thin Films by Phosphorus Doping Dipta Suryya Mahanta, Rudra Narayan Chakraborty, Sethuraman Divagar, Rajalingam Thangavel, Kasilingam Senthilkumar ACS Applied Energy Materials, 2025 Achieving p -type pyrite FeS 2 is essential for its effective use in thin film photovoltaics. Phosphorus (P) is emerging as a prominent anionic dopant in pyrite to induce p -type electrical conductivity. This study investigates the impact of P doping on the structural and electrical characteristics of pyrite thin films. Films are fabricated using DC magnetron sputtering, initially yielding sulfur (S)-poor FeS 2– x phase. Annealing in S atmosphere yields phase-pure pyrite, while coannealing with higher P introduces mixed pyrite-marcasite phase p -type conductivity. An Increasing of band gap from 1.08 to 1.43 eV is also observed, with high hole mobility of 150.62 cm 2 V –1 s –1 . P integration in FeS 2 is confirmed by X-ray photoelectron spectroscopy (XPS) via P–S and Fe–P binding energies. The mixed pyrite-marcasite phase is confirmed by Raman results. This mixed phase p -type FeS 2 can help increase the photovoltaic performance. However, it also shows excessive doping causing nonuniformity and contact behavior.
Integrated Design for High-Efficiency Copper Zinc Tin Sulfide Solar Cells: Harnessing Mg-Alloyed Buffer and Advanced Interface Engineering Santu Mazumder, Mubbasilkhan Ayubkhan Pathan, Dipta Suryya Mahanta, Kasilingam Senthilkumar Langmuir, 2025 The promise of high-efficiency copper zinc tin sulfide or CZTS-based solar cells is hindered by critical challenges such as detrimental defects and problematic interfaces. The conventional ZnS/CZTS junction exhibits a large conduction band offset, leading to a reduced short-circuit current density ( J SC ), while the open-circuit voltage ( V OC ) remains consistently low. Additionally, the use of a toxic CdS layer raises serious environmental and disposal concerns. To address these issues and eliminate degradation at the CZTS/Mo interface, this study explores performance enhancement through systematic optimization of material parameters, including defect density, acceptor concentration, interface quality, electron affinity, and alloying ratio. We introduce TiN as a back contact due to its high reflectance and favorable work function and NiO as an effective hole transport layer. Our analysis reveals that defect density within NiO has a minor effect on device efficiency, whereas increasing acceptor concentration significantly improves built-in potential and band bending, enhancing charge transport. However, the CZTS/NiO interface suffers from severe recombination losses due to lattice mismatch. To further improve performance, we investigate Mg-alloyed ZnS as a buffer layer. By tuning the Mg alloying ratio, we effectively tailor its electrical and optical properties, reducing conduction band offset and minimizing interface losses. The interplay between electron affinity and Mg concentration is shown to be critical for optimal band alignment. Through this integrated approach, we achieve a power conversion efficiency of 18.95% at 300 K using an Mg alloying ratio of 0.45. This work marks a significant step toward high-efficiency, environmentally friendly CZTS solar cells, eliminating reliance on toxic Cd and detrimental MoS x contacts.
Investigation of FeS2 Thin Film as a Hole Transport Layer in CuAl1-xFexS2-Based Solar Cells: A Strategy to Improve Efficiency Rudra Narayan Chakraborty, Dipta Suryya Mahanta, Kasilingam Senthilkumar ACS Applied Energy Materials, 2025 To minimize losses due to recombination in solar cells, the incorporation of a hole transport layer (HTL) has emerged as a promising strategy. However, selecting the appropriate HTL for a given absorber material presents several challenges. This study focuses on modeling and optimization of two solar cell configurations utilizing CuAl 1– x Fe x S 2 [ x = 1 (Cell-1) and 0.75 (Cell-2)] as the absorber material and sputtering deposited FeS 2 thin film as the HTL material to enhance their efficiency using the Silvaco ATLAS device simulator. The deposition of FeS 2 thin film by direct current sputtering, followed by annealing in a sulfur environment, is also demonstrated. The sulfurized thin films exhibit a p -type conductivity. Following the incorporation of HTL and the optimization of different parameters, both solar cells exhibit significantly increased hole current toward back contact, indicating less recombination and efficient charge extraction. The experimental efficiencies of Cell-1 (3.58%) and Cell-2 (5.29%) improved to 7.28% and 9.80% in the simulation with an optimized structure, showing enhancements of 103% and 85%, respectively.
Simulation Study for Nb-Doped MoS2 Layer in CZTS-Based Solar Cells: Assessment of Challenges Santu Mazumder, Supriya Borgohain, Senthilkumar Kasilingam Advanced Theory and Simulations, 2024 The unintentional formation of a layer as a reaction product between the copper zinc tin sulfide (CZTS) thin film and the Mo back contact reduces cell efficiency due to high sheet resistance and carrier recombination. To limit the formation of , an intentionally grown p‐type Nb‐doped layer can serve as an effective hole transport layer. This study presents a detailed study and calculations for CZTS/Mo‐based solar cells, providing guidelines for calibration. Optimizing cell efficiency is influenced by various interconnected factors in Nb‐doped . While a high carrier concentration in Nb‐doped is assumed to enhance efficiency, other parameters such as band state, optical absorption, and carrier mobility also play crucial roles and can limit cell performance. This simulation study evaluated the effect of Nb‐doped layers with different carrier concentrations to determine the optimal conditions for this p‐type layer. This work reveals that a very thin layer (13 nm) of Nb‐doped p‐type can achieve a maximum efficiency of 11.34% (with = 1.5 ) and that for an Nb‐doped p‐type 62 nm is 15.82 % (with = 4.03 ).
Ion implantation induced p-type conductivity in FeS2 thin film Rudra Narayan Chakraborty, Dipta Suryya Mahanta, Santu Mazumder, Kasilingam Senthilkumar Physica Scripta, 2024 In pursuing sustainable energy solutions, thin-film solar cells based on the Copper zinc tin sulfide (CZTS) absorber material have garnered significant attention due to their earth-abundant and non-toxic composition. However, the modest efficiency demonstrated by CZTS solar cells has prompted researchers to investigate novel approaches to improve their performance. An area of potential advancement entails the integration of appropriate hole transport layers (HTLs). In this simulation-based study, we focused on FeS2 as a highly promising candidate for use as an HTL in CZTS-based solar cells. FeS2, traditionally considered n-type, was tailored to achieve p-type conductivity through the negative ion implantation (O, P, and As) process. 40 keV ion beam was utilized, with three doses (105, 1010, 1015 cm−2) applied for each ion beam. We demonstrate successful p-type doping of FeS2 with a hole concentration of ∼1020 cm−3 in case of 1015 cm−2 dose, paving the way for its integration as an effective HTL within the CZTS solar cell structure.
A first principle +U correction to the investigation of intrinsic vacancy and zinc vacancy-cluster induced magnetism in w-ZnO Eliyash Ahmed, K Senthilkumar Physica Scripta, 2023 Pure ZnO shows the probable origin of the magnetic nature. Microscopic correlation to point defect VO and the cluster VZn is obtained by first-principle calculation and +U interaction energy of the p-d orbital subjected to improve band and DOS. Hydrogen contribution to the magnetic moment (MM) due to the coupling of vacancy and 1 s electron correlates with the experimental outcomes. Intrinsic vacancy modulates Fermi surface electron density, leading to the stoner criterion. A higher-order magnetic moment is associated with the cluster vacancy, and the change in the MM has accounted for the +U adjustment to the relevant orbital impact. Nonlinear relations are due to cluster vacancy complexes VZn-x/Oi-x (x = H, 2H), and the FM and AFM exchange has been analyzed. The material encloses large grains; hence, it is advantageous for VZn to develop near the grain edge, and in O-rich environments, chemisorbed O2 is formed near the grain surface.
UV-blue light emission from ZnO nanoparticles Obuliraj Senthilkumar, Kazuki Yamauchi, Kasilingam Senthilkumar, Takahiro Yamamae, Yasuhisa Fujita, Naoki Nishimoto Journal of the Korean Physical Society, 2008
RECENT SCHOLAR PUBLICATIONS
Negative ion implantation enabled controlled oxygen doping in iron pyrite thin films RN Chakraborty, DS Mahanta, KD Devi, K Senthilkumar Small Methods, e01185 , 2026 2026 Citations: 1
Correlation between microstructural changes and phonon shifts in O−-implanted FeS2 thin films RN Chakraborty, DS Mahanta, K Senthilkumar Applied Physics Letters 127 (26) , 2025 2025 Citations: 1
Machine Learning-Driven Optimization of CuAl 1– x Fe x S 2 -based Solar Cells with Oxygen-Implanted FeS 2 Thin Films as the Hole Transport Layer RN Chakraborty, DS Mahanta, K Senthilkumar ACS Applied Energy Materials 8 (22), 17054-17060 , 2025 2025 Citations: 1
Single-step deposition of phase-pure iron pyrite and iron marcasite thin film by sputtering RN Chakraborty, DS Mahanta, K Senthilkumar IN Patent 572,969 , 2025 2025
Interplay of Polymorphism in FeS 2 Thin Films by Phosphorus Doping DS Mahanta, RN Chakraborty, S Divagar, R Thangavel, K Senthilkumar ACS Applied Energy Materials 8 (18), 13519-13528 , 2025 2025 Citations: 1
Integrated Design for High-Efficiency Copper Zinc Tin Sulfide Solar Cells: Harnessing Mg-Alloyed Buffer and Advanced Interface Engineering S Mazumder, MA Pathan, DS Mahanta, K Senthilkumar Langmuir 41 (32), 21402-21414 , 2025 2025
Investigation of FeS 2 Thin Film as a Hole Transport Layer in CuAl 1– x Fe x S 2 -Based Solar Cells: A Strategy to Improve Efficiency RN Chakraborty, DS Mahanta, K Senthilkumar ACS Applied Energy Materials 8 (7), 4272-4280 , 2025 2025 Citations: 6
Simulation Study for Nb‐Doped MoS 2 \rmMoS_2 Layer in CZTS‐Based Solar Cells: Assessment of Challenges S Mazumder, S Borgohain, S Kasilingam Advanced Theory and Simulations 7 (12), 2400396 , 2024 2024 Citations: 3
Ion implantation induced p -type conductivity in FeS 2 thin film RN Chakraborty, DS Mahanta, S Mazumder, K Senthilkumar Physica Scripta 99 (5), 055953 , 2024 2024 Citations: 9
A first principle+ U correction to the investigation of intrinsic vacancy and zinc vacancy-cluster induced magnetism in w-ZnO E Ahmed, K Senthilkumar Physica Scripta 98 (12), 125986 , 2023 2023 Citations: 1
First‐principle investigation of defect‐associated LVM and structural parameter dependency in response to the ground state on‐site Hubbard correction of w ‐ZnO E Ahmed, K Senthilkumar Journal of Raman Spectroscopy 53 (6), 1166-1178 , 2022 2022 Citations: 4
Device study and optimisation of CZTS/ZnS based solar cell with CuI hole transport layer for different conduction band offset S Mazumder, K Senthilkumar Solar Energy 237, 414-431 , 2022 2022 Citations: 39
Device modeling and study of AZO/i-ZnO/ZnS/CZTS-bilayer solar cell for different series and shunt resistances KS S. Mazumder, P. Mazumder Solar Energy 245, 46-57 , 2022 2022 Citations: 30
Unintentional hydrogen doped impurity induced complex paramagnetic centers in ZnO nanoparticles E Ahmed, S Mazumder, K Senthilkumar Solid State Communications 339, 114501 , 2021 2021 Citations: 4
VZn–H complex defect induced ferromagnetic behavior of unintentional hydrogen doped ZnO nanoparticles E Ahmed, K Senthilkumar Materials Science in Semiconductor Processing 123, 105593 , 2021 2021 Citations: 9
Chitosan encapsulated ZnO nanoparticles for labeling applications O Senthilkumar, K Senthilkumar, C Revathi, S Morito, T Ohba, M Sato, ... Journal of Physics: Conference Series 1706 (1), 012016 , 2020 2020 Citations: 3
Anomalous multiphonon features of hyper-Raman in ZnO NPs E Ahmed, R Roy, R Rajaraman, K Senthilkumar IOP Conference Series: Materials Science and Engineering 561 (1), 012031 , 2019 2019
Anomalous multiphonon features of hyper-Raman in ZnO NPs R Rajaraman, E Ahmed, K Senthilkumar, R Roy 2019
Formation of D–V Zn complex defects and possible p-type conductivity of ZnO nanoparticle via hydrogen adsorption K Senthilkumar, T Yoshida, Y Fujita Journal of Materials Science 53 (17), 11977-11985 , 2018 2018 Citations: 16
Photo-induced EPR study of electron trap in ZnO nanoparticles K Senthilkumar, M Subramanian, H Ebisu, M Tanemura, Y Fujita AIP Conference Proceedings 1536 (1), 77-78 , 2013 2013
MOST CITED SCHOLAR PUBLICATIONS
Preparation of ZnO nanoparticles for bio‐imaging applications K Senthilkumar, O Senthilkumar, K Yamauchi, M Sato, S Morito, T Ohba, ... Physica status solidi (b) 246 (4), 885-888 , 2009 2009 Citations: 81
Optimization of nonlinear optical properties of ZnO micro and nanocrystals for biophotonics BE Urban, J Lin, O Kumar, K Senthilkumar, Y Fujita, A Neogi Optical Materials Express 1 (4), 658-669 , 2011 2011 Citations: 42
Bioimaging using the optimized nonlinear optical properties of ZnO nanoparticles BE Urban, P Neogi, K Senthilkumar, SK Rajpurohit, P Jagadeeshwaran, ... IEEE Journal of Selected Topics in Quantum Electronics 18 (4), 1451-1456 , 2012 2012 Citations: 41
Hydrogen related defect complexes in ZnO nanoparticles K Senthilkumar, M Tokunaga, H Okamoto, O Senthilkumar, Y Fujita Applied physics letters 97 (9) , 2010 2010 Citations: 40
Device study and optimisation of CZTS/ZnS based solar cell with CuI hole transport layer for different conduction band offset S Mazumder, K Senthilkumar Solar Energy 237, 414-431 , 2022 2022 Citations: 39
Device modeling and study of AZO/i-ZnO/ZnS/CZTS-bilayer solar cell for different series and shunt resistances KS S. Mazumder, P. Mazumder Solar Energy 245, 46-57 , 2022 2022 Citations: 30
Synthesis of zinc oxide nanoparticles by dc arc dusty plasma K Senthilkumar, O Senthilkumar, S Morito, T Ohba, Y Fujita Journal of Nanoparticle Research 14 (10), 1205 , 2012 2012 Citations: 30
UV-blue light emission from ZnO nanoparticles O Senthilkumar, K Yamauchi, K Senthilkumar, T Yamamae, Y Fujita, ... Journal of the Korean Physical Society, 46-49 , 2008 2008 Citations: 26
Growth of Ga-doped ZnO by MOVPE using diisopropylzinc and tertiary butanol N Nishimoto, T Yamamae, T Kaku, Y Matsuo, K Senthilkumar, ... Journal of Crystal Growth 310 (23), 5003-5006 , 2008 2008 Citations: 22
Trapping and Recombination Properties of the Acceptor-like V Zn -H Complex Defect in ZnO K Senthilkumar, M Subramanian, H Ebisu, M Tanemura, Y Fujita The Journal of Physical Chemistry C 117 (8), 4299-4303 , 2013 2013 Citations: 18
Formation of D–V Zn complex defects and possible p-type conductivity of ZnO nanoparticle via hydrogen adsorption K Senthilkumar, T Yoshida, Y Fujita Journal of Materials Science 53 (17), 11977-11985 , 2018 2018 Citations: 16
Multiphonon scattering and non‐radiative decay in ZnO nanoparticles K Senthilkumar, M Tokunaga, H Okamoto, O Senthilkumar, J Lin, B Urban, ... physica status solidi c 7 (6), 1586-1588 , 2010 2010 Citations: 15
Growth of ZnO thin films by using MOCVD with a high-speed rotating disk reactor N Nishimoto, O Senthilkumar, T Yamamae, K Senthilkumar, Y Fujita Journal of the Korean Physical Society, 2951-2954 , 2008 2008 Citations: 11
Ion implantation induced p -type conductivity in FeS 2 thin film RN Chakraborty, DS Mahanta, S Mazumder, K Senthilkumar Physica Scripta 99 (5), 055953 , 2024 2024 Citations: 9
VZn–H complex defect induced ferromagnetic behavior of unintentional hydrogen doped ZnO nanoparticles E Ahmed, K Senthilkumar Materials Science in Semiconductor Processing 123, 105593 , 2021 2021 Citations: 9
Raman Spectra and Magnetic Property Analysis of Nd-Doped ZnO Thin Films M Subramanian, K Senthilkumar, M Tanemura, T Soga, T Hihara Jpn J Appl Phys 52 (1), 01AC14-01AC14-3 , 2013 2013 Citations: 8
Investigation of FeS 2 Thin Film as a Hole Transport Layer in CuAl 1– x Fe x S 2 -Based Solar Cells: A Strategy to Improve Efficiency RN Chakraborty, DS Mahanta, K Senthilkumar ACS Applied Energy Materials 8 (7), 4272-4280 , 2025 2025 Citations: 6
Deposition of nanoparticle-aggregated ZnO thin films by drop coating method K Senthilkumar, H Okamoto, M Tokunaga, O Senthilkumar, Y Fujita Japanese Journal of Applied Physics 48 (6S), 06FF05 , 2009 2009 Citations: 5
First‐principle investigation of defect‐associated LVM and structural parameter dependency in response to the ground state on‐site Hubbard correction of w ‐ZnO E Ahmed, K Senthilkumar Journal of Raman Spectroscopy 53 (6), 1166-1178 , 2022 2022 Citations: 4
Unintentional hydrogen doped impurity induced complex paramagnetic centers in ZnO nanoparticles E Ahmed, S Mazumder, K Senthilkumar Solid State Communications 339, 114501 , 2021 2021 Citations: 4
