Centre for Nanosciences
Amrita Institute of Medical Sciences,
Amrita Vishwa Vidyapeetham
AIMS Ponekkara P. O., Kochi, Kerala - 682 041, India.

0484 285 8750
researchsecretary@aims.amrita.edu
 

 

Dr. Mariyappan joined as an Assistant Professor at Amrita Center for Nanosciences and Molecular Medicine in June 2016. He obtained his PhD from South Dakota State University, USA in 2011. He has developed advanced gas-phase surface passivation schemes for nanostructured electron acceptors using atomic layer deposition at The Minnesota Nano Center, University of Minnesota. He was a postdoctoral researcher at the College of Nanoscale Science and Engineering, State University of New York, USA, during 2011-2014 and then worked in Worcester Polytechnic Institute for a year. In 2015, he established a research and development division in a Silicon Valley-based startup company, Macromolecular Inc., to develop photovoltaic materials and devices for space PV applications.  

He has published over 20 journal papers including in Nanoscale, ACS Nano and Nano Energy, 20 peer-reviewed conference proceeding papers (IEEE and MRS) and a book chapter. He has been serving as an invited reviewer for 10 journals including ACS Applied Materials & Interfaces, Journal of Applied Physics, Solid State Electronics and AIP Advances.  

Dr. Mariyappan’s research explored various issues in semiconductor materials and devices. His major research areas are defect passivation in semiconductors, device fabrication/characterization, studies on charge transport, bulk and interfacial recombination. His current research includes developing energy harvesting technologies and other opto-electronic devices using emerging nanostructured materials.

Extra Mural Research Funding: "Transformative Approaches for Design and Development of 2-D Carbon Photovoltaics" Awarded by Science and Engineering Research Board (SERB)-2018, Status: Principal Investigator.

Early Career Award: "Chemical Vapor Deposition Assembled 2D Layered Semiconductors Enabled Electrochemical Solar Cells" Science and Engineering Research Board (SERB)-2018.Status: Principal Investigator.

Publications

Publication Type: Journal Article

Year of Publication Title

2019

G. Gopakumar, Ashok, A., Shantikumar V Nair, and Dr. Mariyappan Shanmugam, “Atomically Thin 2D Layered MoS2-enabled Photo-Current Characteristics in TiO2 Nanoparticle Films”, Applied Nanoscience (In Press), 2019.[Abstract]


The present study examines photo-current characteristics of 2D layered molybdenum disulfide (MoS2) incorporated titanium dioxide (TiO2) nanoparticle films at different illumination conditions established using while light (AM1.5), blue (406 nm), and green (525 nm) lasers. Photo-current values, measured from a two-terminal device configuration fabricated using TiO2 nanoparticle films with different weight % of MoS2, were observed to be sensitive to the quantity of MoS2 in the bulk TiO2. It is observed that incorporation of 30 wt% of MoS2 in TiO2 enhanced photo-current up to 48.3% compared to that of pristine TiO2 nanoparticle film under AM1.5 illumination. Blue and green laser-based measurements show that the photo-current is highly sensitive to the weight fraction of MoS2 in TiO2 and incident energy used to generate excitons. The variation observed in the measured photo-current is directly attributed to the optical responsivity of MoS2 to the incoming photons

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2019

A. Ashok, Shantikumar V Nair, and Dr. Mariyappan Shanmugam, “Spray Pyrolysis-Coated Nano-Clustered CdTe on Amorphous Si Thin Films for Heterojunction Solar Cells”, Applied Nanoscience (Switzerland) (In Press), 2019.[Abstract]


Heterojunction solar cells are demonstrated employing spray pyrolysis-processed nano-clustered cadmium telluride (CdTe) on DC-sputtered amorphous silicon (a-Si) as p- and n-type layers, respectively. CdTe and a-Si films were subjected to X-ray photoelectron spectroscopic measurements showing Cd 3d (404.9 eV) and Te 3d (575.8 eV) peaks corresponding to CdTe while the peaks Si 2p (98.3 eV) and Si 2 s (148.3 eV) represent a-Si. Heterojunction solar cells with a stacked structure of FTO/a-Si/CdTe/Al resulted in a photo-conversion efficiency of 2.7% for an optimized thickness values of a-Si (1 µm) and CdTe (6 µm) films. © 2019, King Abdulaziz City for Science and Technology.

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2018

S. H, Dr. Mariyappan Shanmugam, M, M., and J.H., M., “Review on Dye-sensitized Solar Cells based on Polymer Electrolytes”, International Journal of Engineering and Technology(UAE), 2018.

2018

S. N. Vijayaraghavan, Ashok, A., Gopakumar, G., Menon, H., Shantikumar V Nair, and Dr. Mariyappan Shanmugam, “All Spray Pyrolysis-coated CdTe–TiO2 Heterogeneous Films for Photo-Electrochemical Solar Cells”, Materials for Renewable and Sustainable Energy, vol. 7, p. 12, 2018.[Abstract]


Cadmium telluride (CdTe) thin films of different thicknesses deposited onto titanium dioxide (TiO2) nanoparticle layer by spray pyrolysis deposition (SPD) are demonstrated as major photo-active semiconductor in photo-electrochemical solar cell configuration using iodide/triiodide (I−/I3−) redox couple as a hole transport layer. The CdTe–TiO2 heterogeneous films were characterized by X-ray photoelectron spectroscopy which identified doublet split of Cd 3d and Ti 2p which confirms CdTe and TiO2. Optical absorbance and transmittance of CdTe and TiO2 films which were examined by UV–Vis spectroscopy confirm that the optical bandgap of CdTe is 1.5 eV with a dominant photo-absorption in the spectral window of 350–800 nm, while TiO2 showed a bandgap of 3.1 eV and is optically transparent in the visible spectral window. The present work examined photo-anodes comprising 1, 3, 5, and 10 SPD cycles of CdTe coated on TiO2 nanoparticle layer. The solar cell with 5 SPD cycles of CdTe resulting in 0.4{%} efficiency. Results can be articulated to the CdTe deposited by 5 SPD cycles provided an optimum surface coverage in the bulk of TiO2, while the higher SPD cycles leads to agglomeration which blocks the porosity of the heterogeneous films.

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2018

G. Gopakumar, Menon, H., Ashok, A., Shantikumar V Nair, and Dr. Mariyappan Shanmugam, “Two Dimensional Layered Electron Transport Bridges in Mesoscopic TiO2 for Dye Sensitized Solar Cell Applications”, Electrochimica Acta, vol. 267, pp. 63 - 70, 2018.[Abstract]


The present work demonstrates the possibility of facilitating electron transport in mesoscopic titanium dioxide (TiO2) by incorporating nanoflakes of layered molybdenum disulfide (MoS2) as an alternate electron transport bridge. Results suggest that performance of dye sensitized solar cells (DSSCs) can be increased up to ∼16% (from 7.39% to 8.55%) by incorporating 0.2 wt % of MoS2 into the bulk of TiO2, due to the significant improvement in electron lifetime from 8 ms to 23 ms. The nanoflakes of MoS2 form alternate electron transport bridges in the bulk TiO2 nanoparticle film through which photo-injected electrons travel more efficiently to reach transparent electrode compared to DSSCs utilize only TiO2 without MoS2. Presence of atomically thin layered MoS2 nanoflakes in the bulk of TiO2 assist the photo-electrons to skip electron-hole capture processes occur through TiO2 surface states to avoid the interfacial recombination. Further increment in the concentration of MoS2 suppresses the resulting DSSC performance by blocking the porosity which results in less dye adsorption and hence lower photocurrent values

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2018

A. Ashok, Vijayaraghavan, S. N., Unni, G. E., Shantikumar V Nair, and Dr. Mariyappan Shanmugam, “On the Physics of Dispersive Electron Transport Characteristics in SnO 2 Nanoparticle-based Dye Sensitized Solar Cells”, Nanotechnology, vol. 29, p. 175401, 2018.[Abstract]


The present study elucidates dispersive electron transport mediated by surface states in tin oxide (SnO 2 ) nanoparticle-based dye sensitized solar cells (DSSCs). Transmission electron microscopic studies on SnO 2 show a distribution of ∼10 nm particles exhibiting (111) crystal planes with inter-planar spacing of 0.28 nm. The dispersive transport, experienced by photo-generated charge carriers in the bulk of SnO 2 , is observed to be imposed by trapping and de-trapping processes via SnO 2 surface states present close to the band edge. The DSSC exhibits 50% difference in performance observed between the forward (4%) and reverse (6%) scans due to the dispersive transport characteristics of the charge carriers in the bulk of the SnO 2 . The photo-generated charge carriers are captured and released by the SnO 2 surface states that are close to the conduction band-edge resulting in a very significant variation; this is confirmed by the hysteresis observed in the forward and reverse scan current–voltage measurements under AM1.5 illumination. The hysteresis behavior assures that the charge carriers are accumulated in the bulk of electron acceptor due to the trapping, and released by de-trapping mediated by surface states observed during the forward and reverse scan measurements

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2018

G. Gopakumar, Ashok, A., Vijayaraghavan, S. N., Shantikumar V Nair, and Dr. Mariyappan Shanmugam, “MoO3 Surface Passivation on TiO2: An Efficient Approach to Minimize Loss in Fill Factor and Maximum Power of Dye Sensitized Solar Cell”, Applied Surface Science, vol. 447, pp. 554 - 560, 2018.[Abstract]


The present study demonstrates the possibility for improving the performance of dye sensitized solar cell (DSSC) only by minimizing the loss in fill factor (FF) and maximum power point (PMAX) which can be achieved by passivating the nanocrystalline titanium dioxide (TiO2) using physical vapor deposited molybdenum trioxide (MoO3) thin films. The effect of MoO3 coated TiO2 on charge carrier transport was examined in resulting DSSCs and observed that  ∼14% enhancement in efficiency is possible for 5 min passivation of MoO3 on TiO2. The physical vapor deposited MoO3 films were  ∼75% transparent in the spectral range of 350–800 nm with an optical bandgap of  ∼3.1 eV. The wide bandgap MoO3 films facilitate the incoming photons to reach the sensitizing dye to generate excitons. The 14% enhancement in the performance of DSSC by MoO3 passivation is observed through improving only the FF and PMAX while it does not contribute anything significantly to current density and open circuit voltage. Electrochemical impedance spectroscopic studies further confirmed these observations through photo-electron lifetime, which remains constant both in the bulk of pristine TiO2 and MoO3 passivated TiO2 and it further confirms the effect of MoO3 passivation on FF and PMAX in DSSCs.

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2018

A. Ashok, Gopakumar, G., Vijayaraghavan, S. N., Shantikumar V. Nair, and Dr. Mariyappan Shanmugam, “Understanding Hysteresis Behavior in SnO2 Nanofiber Based Dye Sensitized Solar Cell”, Journal of Photovoltaics , 2018.[Abstract]


Tin oxide (SnO2) nanofiber-based dye-sensitized solar cell (DSSC) exhibits an anomalous hysteresis effect on its current–voltage characteristics. While the one-dimensional nature of SnO2 nanofibers is considered facilitating effective charge transport in DSSCs, the surface states present in the SnO2 bandgap are observed to be playing an influential role in trapping and detrapping of charge carriers in the bulk as confirmed by electrochemical impedance spectroscopic studies. Forward and backward electrical bias sweeps identify the hysteresis effect in the performance of resulting DSSCs due to which 43% difference was observed in the photovoltaic performance. Charge carriers generated in the dye utilize the SnO2 nanofiber as a transport medium to reach electrode through energetically active SnO2 surface states which effectively trap and detrap the photogenerated charges during the transport resulting in the hysteresis effect. The observed hysteresis effect varies the maximum power density (PMAX) and fill factor (FF) of the resulting DSSC by 35% and 25%, respectively, between forward and backward scans. The significant change in PMAX and FF asserts that trapping and detrapping mediated charge transport process contributed to the variation in overall performance by 43%.

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2018

A. Ashok, Mathew, S. E., Shivaram, S. B., Dr. Sahadev Shankarappa, Shantikumar V. Nair, and Dr. Mariyappan Shanmugam, “Cost Effective Natural Photo-sensitizer from Upcycled Jackfruit Rags for Dye Sensitized Solar Cells”, Journal of Science: Advanced Materials and Devices, p. -, 2018.[Abstract]


Abstract Photo-sensitizers, usually organic dye molecules, are considered to be one of the most expensive components in dye sensitized solar cells (DSSCs). The present work demonstrates a cost effective and high throughput upcycling process on jackfruit rags to extract a natural photo-active dye and its application as a photo-sensitizing candidate on titanium dioxide (TiO2) in DSSCs. The jackfruit derived natural dye (JDND) exhibits a dominant photo-absorption in a spectral range of 350 nm-800 nm with an optical bandgap of ∼1.1 eV estimated from UV-Visible absorption spectroscopic studies. The \{JDND\} in \{DSSCs\} as a major photo-absorbing candidate exhibits a photo-conversion efficiency of ∼1.1 % with short circuit current density and open circuit voltage of 2.2 mA.cm-2 and 805 mV respectively. Further, the results show that concentration of \{JDND\} plays an influential role on photovoltaic performance of the \{DSSCs\} due to the significant change in photo-absorption, exciton generation and electron injection into TiO2. The simple, high throughput method used to obtain \{JDND\} and the resulting \{DSSC\} performance can be considered as potential merits establishing a cost effective excitonic photovoltaic technology.

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2018

H. Menon, Gopakumar, G., Vijayaraghavan, S. N., Shantikumar V Nair, and Dr. Mariyappan Shanmugam, “2D Layered MoS2 Incorporated TiO2 Nanofiber Based Dye Sensitized Solar Cells”, ChemistrySelect , 2018.

2017

A. Ashok, Vijayaraghavan, S. N., Shantikumar V Nair, and Dr. Mariyappan Shanmugam, “Molybdenum Trioxide Thin Film Recombination Barrier Layers for Dye Sensitized Solar Cells”, RSC Advances , vol. 7, pp. 48853-48860, 2017.[Abstract]


A physical vapor deposition based molybdenum trioxide (MoO3) thin film is demonstrated as an efficient reverse-electron recombination barrier layer (RBL) at the fluorine doped tin oxide (FTO)/titanium dioxide (TiO2) interface in dye sensitized solar cells (DSSCs). Thin films of MoO3 show an average optical transmittance of ∼77% in a spectral range of 350–800 nm with bandgap value of ∼3.1 eV. For an optimum thickness of MoO3, deposited for 5 minutes, the resulting DSSCs showed 15% enhancement in efficiency (η) compared to the reference DSSC which did not use MoO3 RBL; this suggests that MoO3 is effectively suppressing interfacial recombination at the FTO/TiO2 interface. Further, increasing the thickness of MoO3 RBL at the FTO/TiO2 interface (20 minutes deposition) is observed to impede charge transport, as noticed with 55% reduction in η compared to the reference DSSC. Thin film MoO3 RBL with an optimum thickness value at the FTO/TiO2 interface efficiently blocks the leaky transport pathways in the mesoporous TiO2 nanoparticle layer and facilitates efficient charge transport as confirmed by electrochemical impedance spectroscopy.

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Publication Type: Conference Proceedings

Year of Publication Title

2018

A. Ashok, Gopakumar, G., Shantikumar V. Nair, and Dr. Mariyappan Shanmugam, “FTO/TiO2 Interface Engineering by MoO3 Thin Films for Dye Sensitized Solar Cell Applications”, Third International Conference on Nanomaterials: Synthesis, Characterization and Applications. Mahatma Gandhi University, Kottayam, Kerala, India., 2018.

2018

G. Gopakumar, Ashok, A., Shantikumar V. Nair, and Dr. Mariyappan Shanmugam, “2D Layered MoS2 Enabled Photo-responsive Characteristics in TiO2 Nanoparticle Film”, Third International Conference on Nanomaterials: Synthesis, Characterization and Applications. Mahatma Gandhi University, Kottayam, Kerala, India, 2018.

2018

S. N. Vijayaraghavan, Menon, H., Gopakumar, G., Dr. Mariyappan Shanmugam, and Shantikumar V. Nair, “Studies on Charge Transport and Recombination in MoO3 Coated SnO2 Based Dye Sensitized Solar Cells”, Third International Conference on Nanomaterials: Synthesis, Characterization and Applications. Mahatma Gandhi University, Kottayam, Kerala, India., 2018.

2018

H. Menon, Gopakumar, G., Vijayaraghavan, S. N., Dr. Mariyappan Shanmugam, Ashok, A., and Shantikumar V Nair, “Effect of 2D Layered WS2 Nanoflakes on SnO2 Based Dye Sensitized Solar Cell Performance”, Third International Conference on Nanomaterials: Synthesis, Characterization and Applications. Mahatma Gandhi University, Kottayam, 2018.

2018

G. Gopakumar, Ashok, A., Shantikumar V. Nair, and Dr. Mariyappan Shanmugam, “Hydrothermal Assisted Heterogeneous MoS2 Enabled Performance Enhancement in Dye Sensitized Solar Cells”, Third International Conference on Nanomaterials: Synthesis, Characterization and Applications. Mahatma Gandhi University, Kottayam, Kerala, India., 2018.

2018

A. Ashok, Shantikumar V Nair, and Dr. Mariyappan Shanmugam, “Studies on Defect Mediated Charge Transport and Recombination Dynamics in SnO2 Based Dye Sensitized Solar Cells”, Third International Conference on Nanomaterials: Synthesis, Characterization and Applications. Mahatma Gandhi University, Kottayam, Kerala, 2018.

2018

S. V. K, Ashok, A., Shantikumar V. Nair, and Dr. Mariyappan Shanmugam, “Graphene Quantum Dots Enabled Photoabsorption in Mesoporous TiO2 for Excitonic Solar Cell Application”, Third International Conference on Nanomaterials: Synthesis, Characterization and Applications. Mahatma Gandhi University, Kottayam, Kerala, India., 2018.

2017

G. E. Unni, Nair, S. V., and Dr. Mariyappan Shanmugam, “Two Dimensional SnO2 Nanoplates for Efficient Photo-electron Transport in Excitonic Solar Cells”, Nano India. IIT Delhi, India., 2017.

2017

G. Gopakumar, Menon, H., Nair, S. V., and Dr. Mariyappan Shanmugam, “MoS2 Layered Semiconductor: An Efficient Electron Transport Bridge in Mesoscopic Electron Acceptor for Dye Sensitized Solar Cell Applications”, Nano India. IIT Delhi, India., 2017.

2017

A. Ashok, Unni, G. E., Raghavan, V., Dr. Mariyappan Shanmugam, and Nair, S. V., “Spray Pyrolysis Deposited CdTe/CdS Thin Film Heterojunction for Photovoltaic Applications”, Nano India. IIT Delhi, India., 2017.

Dr. Mariyappan Shanmugam
Asst. Professor, Nanosciences, Center for Nanosciences, Kochi

mshanmugham@aims.amrita.edu