Dr. Sudip Kumar Batabyal is the Senior Research Scientist in ACIRI. Prior to joining ACIRI in 2015, Sudip has over 8 years of research experience in nanomaterials fabrication and application in renewable energy sector. His areas of expertise and research interests include semiconducting nanomaterials for energy harvesting and storage, perovskite materials, printed electronics, and energy storage. Sudip received his M.Sc in Physics from Vinoba Bhave University and Ph.D from Indian Association for the Cultivation of Science ( Jadavpur University).

Sudip worked in National University of Singapore on metal coordinated gel and co-ordination polymeric nanofiber from 2007 to 2010. After that he shifted to Energy Research Institute @ Nanyang Technological University (ERI@N) and started work on the project of solution processed Cu2InGa(S/Se)2 (CIGS) and Cu2SnZn(S/Se)4 solar cell. He developed the CIGS and CZTS absorber layer deposition on Mo substrate by spray pyrolysis method. He successfully fabricated the solution processed CIGS device with more than 10% efficiency.

In his research career, he has focused on a wide variety of novel materials (metal chalcogenide, metal oxide, organic semiconductors, carbon nanotubes and graphene) synthesised by a range of fabrication procedures. His main emphasis was on the electronic and optical properties of these materials and direct application of these nanostructures in practical devices. His primary research interests are photovoltaics, photoelectrochemical systems and energy storage. His research work has been published (~80 publications) in many high impact factor journals such as Nature Communication, Advanced Materials, ACS Nano and Advanced Energy Materials etc.

Doctoral research work

  • 2001-2005: Indian Association for the Cultivation of Science, Kolkata, India on synthesis and characterization of some novel nanomaterials under the guidance of Prof.Chitra Basu since March 2001.

Postdoctoral Research work

  1. 2006-2010: National University of Singapore under the supervision of Prof. J. J. Vittal from 2006 to 2009 on semiconducting nanomaterials and metal co-ordinated polymeric nanofiber (metalo gel).
  2. 2010-2015: Working as a senior scientist in the Energy Research Institute @NTU, Nanyang Technological University on thinfilm photovoltaic devices. I supervised the group activity of CIGS group. We developed some solution phase fabrication technique of CIGS solar cell for economic and large scale production. Along with the CIGS and CZTS type devices, I also worked on the other p-n junction photovoltaics devices and DSSC. We developed different metal sulfide and oxide composite nanostructures and use them for solar water splitting and for energy storage in Li and Na ion battery.

Research Interest

Solution Processed PhotovoltaicSolution Processed Photovoltaic Device Device: High fabrication cost of solar cell is the main obstacle for the wide spread application of the solar energy harvesting. Our aim is to develop simple cost effective technology for the fabrication of high efficient solar cell from solution chemistry. We are mainly focused on the thin film PV devices and third generation solar cell.


Nano materials for energy hNano materials for energy harvestingarvesting: Our Main emphasis is on the synthesis and application semiconducting nanomaterials for energy harvesting. Because of size dependent properties we can tune the band gap of the materials and can synthesised selective band gap materials for device application. Also we are interested to modify the surface chemistry of the nanomaterials for the selective application.


Materials developmMaterials development for solar water splittingent for solar water splitting: We are interested for conversion of the solar energy into chemical fuels (H2) by photocatalytic reactions and conversion of the greenhouse gas CO 2 into hydrocarbons fuels via photocatalytic reactions. Our main focus is to development of electrode materials for photoelectrochemical energy harvesting by understanding the electronic properties of the materials such as carrier concentration, mobility, trap density, carrier diffusion length and interaction with the electrolyte.

Electro ChemicalElectro Chemical Energy storage Energy storage: Energy storage devices and systems have an important role in realizing the renewable energy future for our society. So to spread the application of renewable energy we have to develop cost effective energy storage devices. We are interested on the development of low-cost, nanostructured materials and composite materials for high-performance electrode for electrochemical energy storage systems. The synthetic methodology will be environmentally friendly and compatible with large-scale processing for energy storage systems including lithium, sodium batteries and electrochemical capacitors.



  • Development of novel anode material for Na ion battery with high capacity. News coverage by number of news agency, few are listed bellow Reuters Businesswire (#.Uy6tHKiSySo)
  • NANOROSE (fesem image of ZnTeO3) got the best picture awards from American Chemical Society (ACS) community website ACS Nanotation. The news covered by the NUS highlight and ACS publication news livewire.
  • Best Oral Presentation Award at International Conference on Nano-materials: Synthesis, Characterisation and Application. November 4-6, 2004, Kolkata, India.
  • Got invitation for chairing a session in Symposium M (New route to the synthesis of inorganic nanostructured materials) of ICMAT 2007, Singapore.
  • Qualified in Gate 2000, CSIR-NET 2000, CSIR-NET 2001.
  • Reviewed scientific papers routinely from reputed international publishers, like RSC (Energy and Environmental Science, Chemical Communication, JMC, PCCP), ACS (ACS Nano, Chem  matt, JPC, ACS applied Materials and Interfaces,Crystal growth and design), IOP( Nanotechnology, J. of Physics D), Electro Chemical Society (Electrochemical Communication) and Elsevier ( Journal of Alloys and compounds, Materials science and engineering B and so on).


Publication Type: Journal Article
Year of Publication Publication Type Title
2016 Journal Article Z. Li, Boix, P. P., Xing, G., Fu, K., Kulkarni, S. A., Batabyal Sudip Kumar, Xu, W., Cao, A., Sum, T. Chien, Mathews, N., and , “Carbon nanotubes as an efficient hole collector for high voltage methylammonium lead bromide perovskite solar cells”, Nanoscale, 2016.[Abstract]

A high open circuit voltage (VOC) close to 1.4 V under AM 1.5, 100 mW cm−2 conditions is achieved when carbon nanotubes (CNTs) are used as a hole conductor in methyl ammonium lead bromide (MAPbBr3) perovskite solar cells. Time-resolved photoluminescence and impedance spectroscopy investigations suggest that the observed high VOC is a result of the better charge extraction and lower recombination of the CNT hole conductor. Tandem solar cells with all perovskite absorbers are demonstrated with a MAPbBr3/CNT top cell and a MAPbI3 bottom cell, achieving a VOC of 2.24 V in series connection. The semitransparent and high voltage MAPbBr3/CNT solar cells show great potential for applications in solar cell windows, tandem solar cells and solar driven water splitting.

More »»
2016 Journal Article Batabyal Sudip Kumar, Lu, S. Eb, and Vittal, J. Jb, “Synthesis, Characterization, and Photocatalytic Properties of In2S3, ZnIn2S4, and CdIn2S4 Nanocrystals”, Crystal Growth and Design, vol. 16, pp. 2231-2238, 2016.[Abstract]

A one-pot method has been employed to synthesize the nanocrystals of In2S3, ZnIn2S4, and CdIn2S4. The single-source precursor [In(bipy)(SC{O}Ph)3] has been used for making In2S3 nanocrystals. On the other hand, [Zn(SC{O}Ph)2]·2H2O or [Cd(SC{O}Ph)2]·2H2O was reacted with [In(bipy)(SC{O}Ph)3] and decomposed to make the corresponding ternary metal indium sulfides. The nanocrystals have been characterized by X-ray powder diffraction (XRPD), transmission (TEM) and scanning electron microscopies (SEM), selected area electron diffraction (SAED) patterns, and energy-dispersive X-ray analysis (EDX). Parameters such as temperature, molar ratio of precursor to surfactant, duration of reaction time, and surfactant type were varied to investigate their influence on the morphology and size of nanomaterial. It was found that In2S3 exhibits different morphologies under different reaction conditions whereas the effect of these reactions conditions on the morphological evolution is not very prominent for ZnIn2S4 and CdIn2S4. All the synthesized metal ternary In2S3 showed efficient photocatalytic degradation of dye under ultraviolet (UV) light irradiation. We observed that the degradation of dye is much faster in chloroform than in the aqueous solution as the dispersion of nanoparticles is more homogeneous in chloroform solution. A comparison of the photocatalytic activity of In2S3 with ZnIn2S4 and CdIn2S4 having similar morphology and size shows that the photocatalytic activity of the ternary chalcogenides of In2S3 is considerably enhanced. © 2016 American Chemical Society.

More »»
2015 Journal Article X. Wang, Li, Z., Xu, W., Kulkarni, S. A., Batabyal Sudip Kumar, Zhang, S., Cao, A., and Wong, L. Helena, “TiO2 nanotube arrays based flexible perovskite solar cells with transparent carbon nanotube electrode”, Nano Energy, vol. 11, pp. 728 - 735, 2015.[Abstract]

Abstract A solid-state, flexible solar cell based on titanium (Ti) foil/TiO2 nanotubes (TNTs) with organic–inorganic halide perovskite absorber and transparent carbon nanotube electrode is demonstrated. \{TNT\} arrays together with an inherent blocking layer were simultaneously formed on Ti foil during one-step anodization. \{TNT\} arrays serve as deposition scaffold and electron conductor for perovskite absorber. Transparent conductive carbon nanotube network is laminated on top of perovskite and serves as hole collector as well as transparent electrode for light illumination. Under \{AM\} 1.5, 100 mW cm−2 illumination, power conversion efficiency of 8.31% has been achieved, which is among the highest for TiO2 nanotube based flexible solar cells. Interestingly, up to 100 mechanical bending cycles show little deterioration to the device performance, demonstrating good flexibility of the Ti foil based perovskite solar cells. The Ti foil based solid-state, flexible perovskite solar cells have great potential for applications in building photovoltaics and wearable electronic devices.

More »»
2015 Journal Article M. Nguyen, Ernits, K., Tai, K. Fai, Ng, C. Fan, Pramana, S. Snellius, Sasangka, W. A., Batabyal Sudip Kumar, Holopainen, T., Meissner, D., Neisser, A., and H.Wong, L., “ZnS buffer layer for Cu 2 ZnSn (SSe) 4 monograin layer solar cell”, Solar Energy, vol. 111, pp. 344 - 349, 2015.[Abstract]

Abstract Copper zinc tin sulfo-selenide Cu2ZnSn(SSe)4 (CZTSSe) is a low-cost alternative semiconductor material that can be used as an absorber in solar cells. CdS deposited by chemical bath deposition (CBD) is the most efficient buffer layer for Cu2ZnSn(SSe)4 and Cu(InGa)(SSe)2 (CIGS) solar cells. However, there is a strong demand for the development of a Cd-free buffer layer due to the toxicity of Cd and its associated concerns with respect to the disposal and long term safety of Cd containing solar modules. In this work, we report for the first time, the successful use of a ZnS buffer layer for \{CZTSSe\} monograin solar cell that shows similar functionality level as a CdS buffer layer. ZnS buffer layer was deposited onto \{CZTSSe\} absorber layer by employing a scalable non-vacuum \{CBD\} method. The effect of morphology, thickness, as well as chemical composition of the ZnS buffer layer on the efficiency of the \{CZTSSe\} solar cell was investigated, and the best \{CZTSSe\} monograin solar cell had an efficiency of 4.50 (±0.16)%. External quantum efficiency (EQE) showed higher transmission in the blue light region for the ZnS buffer compared to CdS. Increased number of ZnS layers decreased the \{EQE\} signal in 400–800 nm regions, resulting in decreased J–V parameters, suggesting a single layer of 10–25 nm ZnS as a most efficient alternative buffer for CZTSSe.

More »»
2015 Journal Article G. Kumar Dalapati, Batabyal Sudip Kumar, Masudy-Panah, S., Su, Z., Kushwaha, A., Wong, T. It, Liu, H. Fei, Bhat, T., Iskander, A., Lim, Y. - F., Wong, L. Helena, Tripathy, S., and Chi, D., “Sputter grown sub-micrometer thick Cu 2 ZnSnS 4 thin film for photovoltaic device application”, Materials Letters, vol. 160, pp. 45 - 50, 2015.[Abstract]

Abstract Structural properties and solar cells performance of sputter grown sub-micrometer thick ( 600 nm) Cu2ZnSnS4 (CZTS) films are investigated for low cost and large scale photovoltaic deployment. The \{CZTS\} films are deposited using single quaternary stoichiometric target at room temperature. X-ray diffraction, micro-Raman spectroscopy, and scanning electron microscopy measurements were carried out to investigate the structural property and secondary phase formation. The intense phonon peak at 334 cm−1 in the visible Raman spectra confirms the deposition of single phase \{CZTS\} films. CZTS-based thin film solar cells show excellent performance with open circuit voltage  600 mV and over all cell efficiency of  3.07%, exhibiting commercial potential toward large scale fabrication of photovoltaic devices.

More »»
2015 Journal Article Z. Su, Tan, J. Ming Rui, Li, X., Zeng, X., Batabyal Sudip Kumar, and Wong, L. Helena, “Cation Substitution of Solution-Processed Cu2ZnSnS4 Thin Film Solar Cell with over 9% Efficiency”, Advanced Energy Materials, vol. 5, 2015.[Abstract]

To alleviate the limitations of pure sulfide Cu 2 ZnSnS 4 (CZTS) thin film, such as band gaps adjustment, antisite defects, secondary phase and microstructure, Cadmium is introduced into CZTS thin film to replace Zn partially to form Cu 2 Zn 1− x Cd x SnS 4 (CZCTS) thin film by low-cost sol–gel method. It is demonstrated that the band gaps and crystal structure of CZCTS thin films are affected by the change in Zn/Cd ratio.

More »»
2015 Journal Article A. A. Mikhaylov, Medvedev, A. G., Mason, C. W., Nagasubramanian, A., Madhavi, S., Batabyal Sudip Kumar, Zhang, Q., Gun, J., Prikhodchenko, P. V., and Lev, O., “Graphene oxide supported sodium stannate lithium ion battery anodes by the peroxide route: low temperature and no waste processing”, Journal of Materials Chemistry A, vol. 3, pp. 20681–20689, 2015.[Abstract]

Since there has been a notable improvement in the performance of graphene-supported tin-based lithium ion battery anodes, they have become a viable alternative to state of the art graphite anodes. However, currently these anodes are produced by energy-demanding thermal processes and generate lithium chloride or other wastes. In this research, we demonstrate the formation of efficient and stable lithium ion battery anodes based on sodium stannate-coated reduced graphene oxide. Coating is performed at low temperatures and when a sodium peroxostannate precursor is used, the process can be carried out with zero waste discharge. Thermal treatment is required only for the solid material. The anode exhibited a charge capacity of 610 mA h g−1 after 140 cycles at 100 mA g−1. This is the first characterization of a sodium stannate-based anode for LIBs.

More »»
2015 Journal Article J. Sun, Nalla, V., Nguyen, M., Ren, Y., Chiam, S. Yang, Wang, Y., Tai, K. Fai, Sun, H., Zheludev, N., Batabyal Sudip Kumar, and Wong, L. H., “Effect of Zn(O,S) buffer layer thickness on charge carrier relaxation dynamics of CuInSe2 solar cell”, Solar Energy, vol. 115, pp. 396 - 404, 2015.[Abstract]

Abstract A pinhole free Zn(O,S) buffer layer was deposited on CuInSe2 (CIS) absorber by chemical bath deposition (CBD) method. Thin Zn(O,S) exhibits better power conversion efficiency (PCE) at lower thickness. Enhancement of \{PCE\} from 1.5% to 3.9% was observed for electrodeposited \{CIS\} photovoltaic device when the buffer layer thickness reduces from 50 nm to 20 nm. Although the conduction band offset (CBO) at Zn(O,S)/CIS interface are almost identical for both the 20 nm and 50 nm thick buffer layers, investigation on charge carrier dynamics reveals that the carrier lifetime for the 20 nm buffer is much longer than the 50 nm buffer. This offers a plausible explanation for the higher Jsc of the device with 20 nm buffer layer compared to the device with 50 nm buffer layer.

More »»
2015 Journal Article M. Wang, Batabyal Sudip Kumar, Lim, H. Min, Li, Z., and Lam, Y. Ming, “Formation of CuIn (S x Se 1− x) 2 microcrystals from CuInSe 2 nanoparticles by two step solvothermal method”, Journal of Alloys and Compounds, vol. 618, pp. 522 - 526, 2015.[Abstract]

Abstract Here we introduced a two-step reaction to synthesize highly crystalline CuIn(S1−xSex)2 (CuInSSe) microcrystals from CuInSe2 nanocrystals. CuInSSe micro particles can be obtained without toxic selenization or sulfurization process and the composition of sulfur and selenium can be easily controlled by varying the amount of precursor at different stages of the reactions. This synthetic route allows a technique that is simple and non-toxic together with the possibility of tuning the composition. XRD, \{HRTEM\} and \{SAED\} analysis of the final product confirmed the pure phase formation of CuInSSe. \{EDAX\} analysis shows the compositions of the final product matched with CuInSSe and the compositions of the product can tune by the reaction parameter. UV–Vis absorption spectra reveals a clear blue shift due to an increase in band gap with the increase of sulfur content. Initial photocurrent response suggests its possibility to be used as absorber materials in thin film solar cells.

More »»
2015 Journal Article W. Lee Leong, Batabyal Sudip Kumar, Kasapis, S., and Vittal, J. J., “Influence of chiral ligands on the gel formation of a Mg (ii) coordination polymer”, CrystEngComm, vol. 17, pp. 8011–8014, 2015.
2015 Journal Article K. Fai Tai, Fu, D., Chiam, S. Yang, Huan, C. Hon Alfred, Batabyal Sudip Kumar, and Wong, L. Helena, “Antimony Doping in Solution‐processed Cu2ZnSn (S, Se) 4 Solar Cells”, ChemSusChem, vol. 8, pp. 3504–3511, 2015.[Abstract]

Kesterite Cu2ZnSn(S,Se)4 (CZTSSe) is obtained using a facile precursor-solution method followed by selenization. Power-conversion efficiency of 6.0 % is achieved and further improved to 8.2 % after doping the absorber with 0.5 mol % Sb. XRD and Raman spectroscopy show similar characteristics for the undoped and doped CZTSSe. Increasing the Sb concentration increases the grain size and lowers the series resistance. However, further Sb doping beyond 0.5 mol % degrades device performance due to lower open-circuit voltage (and therefore lower fill factor). The effect of Sb doping and the doping concentration are investigated by power-dependent and temperature-dependent photoluminescence studies, revealing that trap density is significant reduced with 0.5 mol % Sb doping. Additional doping beyond 0.5 mol % creates more defects that quench the photoexcited carriers and decrease the open-circuit voltage.

More »»
2015 Journal Article D. Y. W. Yu, Batabyal Sudip Kumar, Gun, J., Sladkevich, S., Mikhaylov, A. A., Medvedev, A. G., Novotortsev, V. M., Lev, O., and Prikhodchenko, P. V., “Antimony and antimony oxide@ graphene oxide obtained by the peroxide route as anodes for lithium-ion batteries”, Main Group Metal Chemistry, 2015.[Abstract]

Zero-valent antimony and antimony oxide were deposited on graphene oxide by the recently introduced peroxide deposition route. The antimony@graphene oxide (GO) anode exhibits a charging capacity of 340 mAh g-1 with excellent stability at a current rate of 250 mA g-1 after 50 cycles of lithiation, which is superior to all other forms of antimony anodes that have been reported thus far. The electrode also exhibits a good rate performance, with a capacity of 230 and 180 mAh g-1 at a rate of 500 and 1000 mA g-1, respectively. We attribute the superior performance of the antimony@GO anodes to our coating protocol, which provides a thin layer of nanometric antimony coating on the graphene oxide, and to a small amount of antimony oxide that is left in the anode material after heat treatment and imparts some flexibility. The efficient charge distribution by the large surface area of reduced GO and the expansion buffering of the elastic graphene sheets also contributed to the superior stability of the anode.

More »»
2015 Journal Article M. Anower Hossain, Tianliang, Z., Keat, L. Kian, Xianglin, L., Prabhakar, R. R., Batabyal Sudip Kumar, Mhaisalkar, S. G., and Wong, L. H., “Synthesis of Cu(In,Ga)(S,Se)2 thin films using an aqueous spray-pyrolysis approach, and their solar cell efficiency of 10.5%”, J. Mater. Chem. A, vol. 3, pp. 4147-4154, 2015.[Abstract]

Semiconducting Cu(In{,}Ga)(S{,}Se)2 (CIGSSe) thin-film is prepared by the spray-pyrolysis of aqueous precursor solutions of copper (CuCl2){,} indium (InCl3){,} gallium (GaCl3){,} and sulphur (SC(NH2)2) sources. The non-vacuum approach of making the CIGSSe thin film using environmentally benign halide-based aqueous precursor solutions paves the way for fabricating solar cells at a much cheaper cost. Here{,} gallium (Ga) is incorporated into the host lattice of CuIn(S{,}Se)2 (CISSe) films grown on a Mo-coated soda-lime glass substrate to modify the optoelectronic properties of CIGSSe films. The bandgap engineered{,} Ga-doped CIGSSe film leads to better photovoltaic characteristics and shows one of the highest efficiency for CIGS thin film solar cell made by the non-vacuum deposition of environmentally-friendly precursors. The optimum efficiency of solar cells with the device configuration of glass/Mo/CIGSSe/CdS/i-ZnO/AZO show j-V characteristics of Voc = 0.621 V{,} jsc = 24.29 mA cm-2{,} FF = 69.84%{,} and a power conversion efficiency of 10.54% under simulated AM 1.5{,} 100 mW cm-2 illuminations{,} demonstrating its potential in making a cost-effective thin film solar cell.

More »»
2014 Journal Article Z. Li, Kulkarni, S. A., Boix, P. P., Shi, E., Cao, A., Fu, K., Batabyal Sudip Kumar, Zhang, J., Xiong, Q., Wong, L. Helena, Mathews, N., and Mhaisalkar, S. G., “Laminated carbon nanotube networks for metal electrode-free efficient perovskite solar cells”, ACS Nano, vol. 8, pp. 6797-6804, 2014.[Abstract]

Organic–inorganic metal halide perovskite solar cells were fabricated by laminating films of a carbon nanotube (CNT) network onto a CH3NH3PbI3 substrate as a hole collector, bypassing the energy-consuming vacuum process of metal deposition. In the absence of an organic hole-transporting material and metal contact, CH3NH3PbI3 and CNTs formed a solar cell with an efficiency of up to 6.87%. The CH3NH3PbI3/CNTs solar cells were semitransparent and showed photovoltaic output with dual side illuminations due to the transparency of the CNT electrode. Adding spiro-OMeTAD to the CNT network forms a composite electrode that improved the efficiency to 9.90% due to the enhanced hole extraction and reduced recombination in solar cells. The interfacial charge transfer and transport in solar cells were investigated through photoluminescence and impedance measurements. The flexible and transparent CNT network film shows great potential for realizing flexible and semitransparent perovskite solar cells.

More »»
2014 Journal Article D. Y.W., E., H. Harry, and Batabyal Sudip Kumar, “Bulk antimony sulfide with excellent cycle stability as next-generation anode for lithium-ion batteries”, Scientific reports, vol. 4, 2014.[Abstract]

Nanomaterials as anode for lithium-ion batteries (LIB) have gained widespread interest in the research community. However, scaling up and processibility are bottlenecks to further commercialization of these materials. Here, we report that bulk antimony sulfide with a size of 10–20 μm exhibits a high capacity and stable cycling of 800 mAh g−1. Mechanical and chemical stabilities of the electrodes are ensured by an optimal electrode-electrolyte system design, with a polyimide-based binder together with fluoroethylene carbonate in the electrolyte. The polyimide binder accommodates the volume expansion during alloying process and fluoroethylene carbonate suppresses the increase in charge transfer resistance of the electrodes. We observed that particle size is not a major factor affecting the charge-discharge capacities, rate capability and stability of the material. Despite the large particle size, bulk antimony sulfide shows excellent rate performance with a capacity of 580 mAh g−1 at a rate of 2000 mA g−1.

More »»
2014 Journal Article P. V. Prikhodchenko, Yu, D. Y. W., Batabyal Sudip Kumar, Uvarov, V., Gun, J., Sladkevich, S., Mikhaylov, A. A., Medvedev, A. G., and Lev, O., “Nanocrystalline tin disulfide coating of reduced graphene oxide produced by the peroxostannate deposition route for sodium ion battery anodes”, J. Mater. Chem. A, vol. 2, pp. 8431-8437, 2014.[Abstract]

A highly stable sodium ion battery anode was prepared by deposition of hydroperoxostannate on graphene oxide from hydrogen-peroxide-rich solution followed by sulfidization and 300 [degree]C heat treatment. The material was characterized by electron microscopy{,} powder X-ray diffraction and X-ray photoelectron spectroscopy which showed that the active material is mostly rhombohedral SnS2 whose (001) planes were preferentially oriented in parallel to the graphene oxide sheets. The material exhibited >610 mA h g-1 charge capacity at 50 mA g-1 (with >99.6% charging efficiency) between 0 and 2 V vs. Na/Na+ electrode{,} high cycling stability for over 150 cycles and very good rate performance{,} >320 mA h g-1 at 2000 mA g-1.

More »»
2014 Journal Article J. C. W. Ho, Zhang, T., Lee, K. Keat, Batabyal Sudip Kumar, Tok, A. I. Y., and Wong, L. H., “Spray pyrolysis of CuIn (S, Se) 2 solar cells with 5.9% efficiency: a method to prevent Mo oxidation in ambient atmosphere”, ACS Applied Materials & Interfaces, vol. 6, pp. 6638-6643, 2014.[Abstract]

Direct spray pyrolysis to form CuInS2 (CIS) on molybdenum substrate in ambient environment has been a challenge because of the ease of Mo oxidation at low temperatures. MoO2 formation affects the wettability of precursor solution during spray pyrolysis, which degrades the uniformity of CIS film and acts as a resistive layer for carrier transport. In this paper, Mo oxidation was prevented by using excess sulfur in the precursor solution under a gradual heating and spray process. A thin precursor layer was initially deposited as a barrier layer to prevent oxygen adsorption on Mo surface before the temperature was increased further to form polycrystalline CuInS2. The CuIn(S,Se)2 (CISSe) device fabricated from selenization of the spray-pyrolyzed CIS film exhibited a power conversion efficiency (PCE) of 5.9%. The simple spray method proposed here can be used to deposit a variety of Cu-based chalcopyrite precursor to produce high-quality thin film solar cells.

More »»
2014 Journal Article R. Ramanujam Prabhakar, Loc, N. Huu, Kumar, M. Hemant, Boix, P. P., Juan, S., John, R. Abraham, Batabyal Sudip Kumar, and Wong, L. Helena, “Facile Water-based Spray Pyrolysis of Earth-Abundant Cu2FeSnS4 Thin Films as an Efficient Counter Electrode in Dye-Sensitized Solar Cells”, ACS Applied Materials & Interfaces, vol. 6, pp. 17661-17667, 2014.[Abstract]

A novel approach to produce earth-abundant Cu2FeSnS4 (CFTS) thin film using spray pyrolysis of nontoxic aqueous precursors followed by sulfurization is reported. The CFTS phase formation was confirmed by both Raman spectroscopy and X-ray diffraction techniques. Hall measurements of these films reveal p-type conductivity with good charge carrier density and mobilities appropriate for solar harvesting devices. To the best of our knowledge, this is the first report on the electrical properties of solution-processed Cu2FeSnS4 thin films estimated using Hall measurements. Dye-sensitized solar cells (DSSC) fabricated with CFTS thin film as a photocathode in iodine/iodide electrolyte exhibit good power conversion efficiency, 8.03%, indicating that CFTS would be a promising cheaper alternative to replace Pt as a counter electrode in DSSCs.

More »»
2014 Journal Article L. H. Nguyen, Aravindan, V., Kulkarni, S. A., Yanan, F., Prabhakar, R. Ramanujam, Batabyal Sudip Kumar, and Madhavi, S., “Self‐Assembled Ultrathin Anatase TiO2 Nanosheets with Reactive (001) Facets for Highly Enhanced Reversible Li Storage”, ChemElectroChem, vol. 1, pp. 539–543, 2014.[Abstract]

Highly reversible Li storage is achieved using self-assembled anatase phase TiO2 nanosheets with exposed (001) facets. The obtained devices exhibit excellent cyclability during high-current operation.

More »»
2014 Journal Article J. Sun, Batabyal Sudip Kumar, Tran, P. D., and Wong, L. H., “Electrodeposition of single phase CuInSe 2 for solar energy harvesting: Role of different acidic additives”, Journal of Alloys and Compounds, vol. 591, pp. 127–131, 2014.[Abstract]

Single phase CuInSe2 (CIS) absorber material is required for producing high quality thin film solar cells, as the presence of impurity Cu2−xSe leads to short circuit of the cells. Traditionally, the deposition of single phase CIS requires the use of a suitable chelating agent to shift the Cu2+/Cu redox couple towards the redox potential of the In3+/In couple, and also an acid to adjust the pH of deposition bath around 2. We propose a novel idea of using suitable acids that could concurrently also serve as the chelating agent. Oxalic acid, acetic acid and hydrochloric acid were investigated on their ability to serve this dual function. We found that oxalic acid is the most promising additive because the CIS film deposited was densest and yielded the highest photocurrent.

More »»
2014 Journal Article H. Min Lim, Tan, J. Yi, Batabyal Sudip Kumar, Magdassi, S., Mhaisalkar, S. G., and Wong, L. H., “Photoactive Nanocrystals by Low-Temperature Welding of Copper Sulfide Nanoparticles and Indium Sulfide Nanosheets”, ChemSusChem, vol. 7, pp. 3290–3294, 2014.[Abstract]

We successfully utilize the concept of coalescence and room-temperature sintering to prepare morphologically different nanoparticles. n-Type chalcogenide (CuIn5S8) nanocrystals are synthesized at room temperature by simple mixing of oppositely charged precursor nanoparticles. The coalescence of polycation-coated CuS nanoparticles and negatively charged In2S3 nanoplates is driven by close contact of the particles due to electrostatic interactions. Analysis by X-ray diffraction, transmission electron microscopy (TEM) imaging, and Raman spectroscopy confirms the formation of single-phase CuIn5S8 without traceable secondary phase. In a photovoltaic device, the use of the coalesced particles yields a power conversion efficiency of 1.8 %.

More »»
2014 Journal Article V. Nalla, Ho, J. C. W., Batabyal Sudip Kumar, Wang, Y., Tok, A. I. Y., Sun, H., Wong, L. H., and Zheludev, N., “Photophysical investigation of charge recombination in CdS/ZnO layers of CuIn (S, Se) 2 solar cell”, RSC Advances, vol. 4, pp. 58372–58376, 2014.[Abstract]

Excitation wavelength dependent femtosecond transient photocurrents were measured on CuIn(S,Se)2 solar cell devices, in the range of 330–1300 nm. Below 450 nm wavelength excitations, charge recombination in CdS/ZnO layers is determined to be responsible for longer decays and lower EQE. Femtosecond pump–probe measurements also support the charge transfer and recombination in CdS/ZnO layers. These measurements will be helpful to design high efficiency CISSe solar cells, by selecting suitable buffer layers.

More »»
2014 Journal Article L. H. M., Y., T. J., Batabyal Sudip Kumar, S., M., G., M. S., and G., M. S., “Welding of CuS and In2S3 nanosheets at low temperature: Formation of CuIn5S8 photoactive nanocrystals”, ChemSusChem , vol. 7, pp. 3290 – 3294 , 2014.
2014 Journal Article Y. D. Y.W., V., P. P., W., M. C., Batabyal Sudip Kumar, J., G., S., S., A., M., and O., L., “Novel anode for Na-ion batteries with excellent cycle and rate capability: Sb2S3 nanoparticle decorated graphene composite”, Nature Communication 4, 2014.
2013 Journal Article D. YW, V, P. Petr, W Chad, M., Batabyal Sudip Kumar, Jenny, G., Sergey, S., G Alexander, M., and Ovadia, L., “High-capacity antimony sulphide nanoparticle-decorated graphene composite as anode for sodium-ion batteries”, Nature communications, vol. 4, 2013.[Abstract]

Sodium-ion batteries are an alternative to lithium-ion batteries for large-scale applications. However, low capacity and poor rate capability of existing anodes are the main bottlenecks to future developments. Here we report a uniform coating of antimony sulphide (stibnite) on graphene, fabricated by a solution-based synthesis technique, as the anode material for sodium-ion batteries. It gives a high capacity of 730 mAh g−1 at 50 mA g−1, an excellent rate capability up to 6C and a good cycle performance. The promising performance is attributed to fast sodium ion diffusion from the small nanoparticles, and good electrical transport from the intimate contact between the active material and graphene, which also provides a template for anchoring the nanoparticles. We also demonstrate a battery with the stibnite–graphene composite that is free from sodium metal, having energy density up to 80 Wh kg−1. The energy density could exceed that of some lithium-ion batteries with further optimization.

More »»
2013 Journal Article M. Nguyen, Tran, P. D., Pramana, S. S., Lee, R. Lin, Batabyal Sudip Kumar, Mathews, N., Wong, L. H., and Graetzel, M., “In situ photo-assisted deposition of MoS 2 electrocatalyst onto zinc cadmium sulphide nanoparticle surfaces to construct an efficient photocatalyst for hydrogen generation”, Nanoscale, vol. 5, pp. 1479-1482, 2013.[Abstract]

We reported herein a facile and scalable preparation process for MoS2-decorated ZnxCd1-xS hybrid photocatalysts for hydrogen generation. ZnxCd1-xS nanopowder was first prepared from commercially available precursors employing a solution based process. MoS2 hydrogen evolution reaction catalyst was then loaded onto the ZnxCd1-xS nanopowder via a photo-assisted deposition process which employed mild conditions (room temperature{,} atmospheric pressure and visible light illumination). Thus{,} this process represents an important advantage in the large scale production of semiconductor/MoS2 hybrid photocatalysts in comparison to the conventional method relying on thermal decomposition of (NH4)2[MoS4] precursor at high temperature and under H2S pressure. The best Zn0.2Cd0.8S/MoS2 3% showed two hundred-and-ten times (210 times) faster hydrogen generation rate on visible light illumination compared with that obtained for un-treated Zn0.2Cd0.8S. That was the most impressive catalytic enhancement ever recorded for a semiconductor photocatalyst decorated with a noble metal free electrocatalyst.

More »»
2013 Journal Article A. Mahshid, S., P. Stevin, Batabyal Sudip Kumar, Chris, B., G., M. Subodh, and Ming, L. Yeng, “Synthesis of Cu2SnSe3 nanocrystals for solution processable photovoltaic cells”, Inorganic Chemistry, vol. 52, pp. 1722-1728, 2013.[Abstract]

This paper describes the synthesis of ternary chalcogenide Cu2SnSe3 nanocrystals as an alternative solar absorber material to conventional quaternary CuInxGa1–xSe2. We used the hot coordination solvent method with hexadecylamine as the capping ligand for the first time for this material system. Using a variety of characterization techniques, such as X-ray diffraction, selected area electron diffraction, convergent beam electron diffraction, and Raman spectroscopy, the nanocrystals were found to be monoclinic Cu2SnSe3 with an optical energy band gap of 1.3 eV and have a narrow size distribution. These nanocrystals are shown to be photosensitive in the range of wavelengths corresponding to the solar spectrum, which makes them highly promising as alternative photon absorber materials for photovoltaic applications.

More »»
2013 Journal Article C. Yongan, John, C. W. Ho, Batabyal Sudip Kumar, Wei, L., Yun, S., G., M. Subodh, and H., W. Lydia, “Nanoparticle-Induced Grain Growth of Carbon-Free Solution-Processed CuIn(S,Se)2 Solar Cell with 6% Efficiency”, ACS Applied Materials & Interfaces, vol. 5, pp. 1533-1537, 2013.[Abstract]

Chalcopyrite-based solar cell deposited by solution processes is of great research interest because of the ease of fabrication and cost effectiveness. Despite the initial promising results, most of the reported methods encounter challenges such as limited grain growth, carbon-rich interlayer, high thermal budget, and the presence of secondary Cu-rich phases, which limit the power conversion efficiency (PCE). In this paper, we develop a new technique to deposit large grain, carbon-free CISSe absorber layers from aqueous nanoparticle/precursor mixture which resulted in a solar cell with PCE of 6.2%. CuCl2, InCl3, and thiourea were mixed with CuS and In2S3 nanoparticles in water to form the unique nanoparticle/precursor solution. The Carbon layer formation was prevented because organic solvents were not used in the precursor. The copper-rich (CuS) nanoparticles were intentionally introduced as nucleation sites which accelerate grain growth. In the presence of nanoparticles, the grain size of CISSe film increased by a factor of 7 and the power conversion efficiency of the solar cell is 85% higher than the device without nanoparticle. This idea of using nanoparticles as a means to promote grain growth can be further exploited for other types of chalcopyrite thin film deposited by solution methods.

More »»
2013 Journal Article X. Wang, Kulkarni, S. A., Ito, B. Ieiri, Batabyal Sudip Kumar, Nonomura, K., Wong, C. Cheong, Grätzel, M., Mhaisalkar, S. G., and Uchida, S., “Nanoclay gelation approach towards improved dye-sensitized solar cell efficiencies: an investigation of charge transport and shift in TiO2 conduction band”, ACS Applied Materials & Interfaces, vol. 5, pp. 444-450, 2013.[Abstract]

Nanoclay minerals play a promising role as additives in the liquid electrolyte to form a gel electrolyte for quasi-solid-state dye-sensitized solar cells, because of the high chemical stability, unique swelling capability, ion exchange capacity, and rheological properties of nanoclays. Here, we report the improved performance of a quasi-solid-state gel electrolyte that is made from a liquid electrolyte and synthetic nitrate-hydrotalcite nanoclay. Charge transport mechanisms in the gel electrolyte and nanoclay interactions with TiO2/electrolyte interface are discussed in detail. The electrochemical analysis reveals that the charge transport is solely based on physical diffusion at the ratio of [PMII]:[I2] = 10:1 (where PMII is 1-propyl-3-methylimidazolium iodide). The calculated physical diffusion coefficient shows that the diffusion of redox ions is not affected much by the viscosity of nanoclay gel. The addition of nitrate-hydrotalcite clay in the electrolyte has the effect of buffering the protonation process at the TiO2/electrolyte interface, resulting in an upward shift in the conduction band and a boost in open-circuit voltage (VOC). Higher VOC values with undiminished photocurrent is achieved with nitrate-hydrotalcite nanoclay gel electrolyte for organic as well as for inorganic dye (D35 and N719) systems. The efficiency for hydrotalcite clay gel electrolyte solar cells is increased by 10%, compared to that of the liquid electrolyte. The power conversion efficiency can reach 10.1% under 0.25 sun and 9.6% under full sun. This study demonstrates that nitrate-hydrotalcite nanoclay in the electrolyte not only solidifies the liquid electrolyte to prevent solvent leakage, but also facilitates the improvement in cell efficiency.

More »»
2013 Journal Article X. Zeng, Pramana, S. S., Batabyal Sudip Kumar, Mhaisalkar, S. G., Chen, X., and Jinesh, K. B., “Low temperature synthesis of wurtzite zinc sulfide (ZnS) thin films by chemical spray pyrolysis”, Phys. Chem. Chem. Phys., vol. 15, pp. 6763-6768, 2013.[Abstract]

Zinc sulfide (ZnS) thin films have been synthesized by spray pyrolysis at 310 [degree]C using an aqueous solution of zinc chloride (ZnCl2) and thioacetamide (TAA). Highly crystalline films were obtained by applying TAA instead of thiourea (TU) as the sulfur source. X-ray diffraction (XRD) analyses show that the films prepared by TAA contained a wurtzite structure{,} which is usually a high temperature phase of ZnS. The crystallinity and morphology of the ZnS films appeared to have a strong dependence on the spray rate as well. The asymmetric polar structure of the TAA molecule is proposed to be the intrinsic reason of the formation of highly crystalline ZnS at comparatively low temperatures. The violet and green emissions from photoluminescence (PL) spectroscopy reflected the sulfur and zinc vacancies in the film. Accordingly{,} the photodetectors fabricated using these films exhibit excellent response to green and red photons of 525 nm and 650 nm respectively{,} though the band gaps of the materials{,} estimated from optical absorption spectroscopy{,} are in the range of 3.5-3.6 eV.

More »»
2013 Journal Article L. Hui Min, Gautam, M. Subodh, Stevin, P., Shlomo, M., and Batabyal Sudip Kumar, “Chemical welding of binary nanoparticles: room temperature sintering of CuSe and In2S3 nanoparticles for solution-processed CuInSxSe1-x solar cells”, Chemical Communications, 2013.[Abstract]

Chemical welding of oppositely charged dissimilar metal chalcogenide nanomaterials is reported to produce a quaternary metal chalcogenide. CuSe and In2S3 nanoparticles were synthesized with opposite surface charges by stabilizing with polyacrylic acid and polydiallyldimethylammonium chloride. Upon mixing these nanoparticles at room temperature, the electrostatic attraction induced coalescence of these nanoparticles and led to the formation of CuInSxSe1−x nanoparticles.

More »»
2013 Journal Article W. Mengxi, Yeng-Ming, L., Batabyal Sudip Kumar, Zhenggang, L., and Gautam, M. Subodh, “Nanocrystalline Copper Indium Selenide (CuInSe2) Particles for Solar Energy Harvesting”, RSC Advances, 2013.[Abstract]

High quality copper indium selenide (CuInSe2) nanocrystals were synthesized solvothermally at low temperature (180 °C) using selenite salts (SeO32−) as a dual source for metal and chalcogen, and dimethylformamide (DMF) as one of the solvents and the reducing agent. In order to find out the best solvent combinations for this type of reduction reaction, the effects of different co-solvents on the phase and morphology of the final products were studied in detail. Pure phase CuInSe2 with high crystallinity was synthesized in a methanol–DMF (Me–DMF) system. On the other hand, using water–DMF (H2O–DMF) resulted in some impurity and nanocrystals of poor crystallinity. Raman study revealed that CuInSe2 crystals synthesized in Me–DMF and H2O–DMF exhibit different scattering geometries. The difference of the final products obtained from Me–DMF and H2O–DMF systems may be due to the difference in the reducing ability of methanol and water as well as the difference in the interaction force between the two solvents within each system. Different morphologies such as nanoparticles and nanoplates can be obtained by simply varying the precursor concentration in the mixed solvents. The photo-response of the as-synthesized materials in a 3-electrode photo-electrochemical (PEC) cell suggests that these materials have the potential to be used for solar energy harvesting.

More »»
2013 Journal Article K. R. G. Karthik, Prabhakar, R. Ramanujam, Hai, L., Batabyal Sudip Kumar, Huang, Y. Z., and Mhaisalkar, S. G., “A ZnO nanowire resistive switch”, Applied Physics Letters, vol. 103, p. 123114, 2013.[Abstract]

An individual ZnO nanowire resistive switch is evaluated with Pt/ZnO nanowire/Pt topology. A detailed DC I-V curve analysis is performed to bring both the conduction mechanism and the device characteristics to light. The device is further studied at various vacuum pressures to ascertain the presence of polar charges in ZnO nanowires as the phenomenon leading to the formation of the switch. The disappearance of the resistive switching is also analyzed with two kinds of fabrication approaches Focused Ion/Electron Beam involved in the making the device and a summary of both length and fabrication dependences of resistive switching in the ZnO nanowire is presented.

More »»
2012 Journal Article P. D. Tran, Batabyal Sudip Kumar, Pramana, S. S., Barber, J., Wong, L. H., and Loo, S. Chye Joach, “A cuprous oxide–reduced graphene oxide (Cu 2 O–rGO) composite photocatalyst for hydrogen generation: employing rGO as an electron acceptor to enhance the photocatalytic activity and stability of Cu 2 O”, Nanoscale, vol. 4, pp. 3875-3878, 2012.[Abstract]

Photocorrosion{,} that causes rapid deactivation of Cu2O photocatalysts{,} was addressed by incorporating this oxide in a composite with reduced graphene oxide which acts as an electron acceptor to extract photogenerated electrons from Cu2O. Cu2O-rGO composite engineering also allows enhancing significantly photocatalytic activities of Cu2O for H2 generation.

More »»
2012 Journal Article L. Xi, Tran, P. D., Chiam, S. Yang, Bassi, P. Saurabh, Mak, W. Fatt, Mulmudi, H. Kumar, Batabyal Sudip Kumar, Barber, J., Loo, J. Say Chye, and Wong, L. Helena, “Co3O4-decorated hematite nanorods as an effective photoanode for solar water oxidation”, The Journal of Physical Chemistry C, vol. 116, pp. 13884-13889, 2012.[Abstract]

In this Article, we report a strategy to perform in situ incorporation of oxygen evolution catalyst, Co3O4, during hydrothermal growth of Fe2O3 nanorod arrays. It was found that the highest photocurrent increase and onset potential shift was observed with 5% Co2+. The photocurrent density increases from 0.72 for the pristine Fe2O3 nanorod to 1.20 mA/cm2 at 1.23 V versus RHE (i.e., 67% improvement) with 5% Co2+ added. Concomitant with this improvement was a shift in the onset potential by ∼40 mV and improvements in incident-photon-to-current efficiencies and oxygen evolution. Hematite photoanodes with in situ deposition of Co3O4 nanoparticles showed better performance than those prepared by ex situ procedures because of high surface roughness, larger Co3O4/hematite interfacial area, and smaller Co3O4 particle size.

More »»
2012 Journal Article P. D. Tran, Pramana, S. S., Kale, V. S., Nguyen, M., Chiam, S. Yang, Batabyal Sudip Kumar, Wong, L. H., Barber, J., and Loo, J., “Novel assembly of an MoS2 electrocatalyst onto a silicon nanowire array electrode to construct a photocathode composed of elements abundant on the earth for hydrogen generation”, Chemistry – A European Journal, vol. 18, pp. 13994–13999, 2012.[Abstract]

Mild-mannered catalyst: A novel procedure to load a MoS2 co-catalyst onto the surface of silicon under mild-conditions (room temperature, atmospheric pressure, aqueous solution) by a photo-assisted electrodeposition process employing commercially available precursors is reported. The obtained Si-NW@MoS2 photocathode showed similar catalytic activity for light-driven H2 generation compared with a Si-NW@Pt photocathode (see scheme).

More »»
2012 Journal Article L. H. Nguyen, Mulmudi, H. K., Sabba, D., Kulkarni, S. A., Batabyal Sudip Kumar, Nonomura, K., Gratzel, M., and Mhaisalkar, S. G., “A selective co-sensitization approach to increase photon conversion efficiency and electron lifetime in dye-sensitized solar cells”, Phys. Chem. Chem. Phys., vol. 14, no. 47, pp. 16182-16186, 2012.[Abstract]

Ruthenium-based C106 and organic D131 sensitizers have been judicially chosen for co-sensitization due to their complementary absorption properties and different molecular sizes. Co-sensitization yields a higher light-harvesting efficiency as well as better dye coverage to passivate the surface of TiO2. The co-sensitized devices C106 + D131 showed significant enhancement in the performance ([small eta] = 11.1%){,} which is a marked improvement over baseline devices sensitized with either D131 ([small eta] = 5.6%) or C106 ([small eta] = 9.5%). The improved performance of the co-sensitized cell is attributed to the combined enhancement in the short circuit current{,} open circuit voltage{,} and the fill-factor of the solar cells. Jsc is improved because of the complementary absorption spectra and favorable energy level alignments of both dyes; whereas{,} Voc is improved because of the better surface coverage helping to reduce the recombination and increase the electron life time. The origins of these enhancements have been systematically studied through dye desorption{,} absorption spectroscopy{,} and intensity modulated photovoltage spectroscopy investigations.

More »»
2012 Journal Article P. V. Prikhodchenko, Gun, J., Sladkevich, S., Mikhaylov, A. A., Lev, O., Tay, Y. Yan, Batabyal Sudip Kumar, and Yu, D. Y. W., “Conversion of Hydroperoxoantimonate Coated Graphenes to Sb2S3@Graphene for a Superior Lithium Battery Anode”, Chemistry of Materials, vol. 24, pp. 4750-4757, 2012.[Abstract]

We describe a method for conformal coating of reduced graphene oxide (rGO) by stibnite nanocrystallites. First, graphene oxide (GO) supported amorphous hydroperoxoantimonate was produced using the recently introduced hydrogen peroxide synthesis route. Sulfurization of the amorphous antimonate yielded supported antimony(V) oxide nanoparticles and sulfur, which were then converted by high temperature vacuum treatment to 15–20 nm rGO supported stibnite. The usefulness of the new material and synthesis approach are demonstrated by highly efficient and stable lithium battery anodes. Since both sulfur lithiation and antimony–lithium alloying are reversible, they both contribute to the charge capacity, which exceeded 720 mA h g–1 after 50 cycles at a current density of 250 mA g–1. The very small crystallite size of the stibnite provides a minimum diffusion pathway and allows for excellent capacity retention at a high rate (>480 mA h g–1 at 2000 mA g–1 was observed). The nanoscale dimensions of the crystallites minimize lithiation-induced deformations and the associated capacity fading upon repeated charge–discharge cycles. The flexibility and conductivity of the rGO ensure minimal ohmic drop and prevent crack formation upon repeated cycles.

More »»
2012 Journal Article J. Gun, Kulkarni, S. A., Xiu, W., Batabyal Sudip Kumar, Sladkevich, S., Prikhodchenko, P. V., Gutkin, V., and Lev, O., “Graphene oxide organogel electrolyte for quasi solid dye sensitized solar cells”, Electrochemistry Communications, vol. 19, pp. 108 - 110, 2012.[Abstract]

Low concentration, as low as 0.4 wt.% graphene oxide organogels is reported for different organic solvents. The gelation of organic solvents at exceedingly low concentrations opens the door for the implementation of graphene oxides based electrolytes in various electrochemical applications. Here we demonstrate the use of acetonitrile–graphene oxide (GO) gel containing iodide/triiodide as a quasi-solid electrolyte for dye sensitized solar cells (DSCs). Electrochemical impedance studies reveal that the mass transfer barrier is not adversely affected by the presence of the minute amount of \{GO\} gel former. The achieved energy conversion efficiency (η) for the device without \{GO\} and with 1% \{GO\} gel electrolytes is 6.9% and 7.5% respectively under one sun illumination.

More »»
2012 Journal Article P. D. Tran, Xi, L., Batabyal Sudip Kumar, Wong, L. H., Barber, J., and Loo, J. Say Chye, “Enhancing the photocatalytic efficiency of TiO2 nanopowders for H2 production by using non-noble transition metal co-catalysts”, Phys. Chem. Chem. Phys., vol. 14, pp. 11596-11599, 2012.[Abstract]

Co and Ni-nanoclusters are attractive alternatives to Pt catalysts for hydrogen generation. These earth abundant elements when loaded onto the TiO2 nanopowders surface act as efficient co-catalysts. Co{,} Ni-decorated TiO2 photocatalysts display only three (3) times lower catalytic activities for H2 evolution under UV illumination compared with Pt-decorated TiO2 photocatalysts.

More »»
2012 Journal Article L. Zhang, Mulmudi, H. Kumar, Batabyal Sudip Kumar, Lam, Y. Ming, and Mhaisalkar, S. Gautam, “Metal/metal sulfide functionalized single-walled carbon nanotubes: FTO-free counter electrodes for dye sensitized solar cells”, Phys. Chem. Chem. Phys., vol. 14, no. 28, pp. 9906-9911, 2012.[Abstract]

The use of single-walled carbon nanotubes (CNT) thin films to replace conventional fluorine-doped tin oxide (FTO) and both FTO and platinum (Pt) as the counter electrode in dye sensitized solar cells (DSSC) requires surface modification due to high sheet resistance and charge transfer resistance. In this paper{,} we report a simple{,} solution-based method of preparing FTO-free counter electrodes based on metal (Pt) or metal sulfide (Co8.4S8{,} Ni3S2) nanoparticles/CNT composite films to improve device performance. Based on electrochemical studies{,} the relative catalytic activity of the composite films was Pt > Co8.4S8 > Ni3S2. We achieved a maximum efficiency of 3.76% for the device with an FTO-free counter electrode (Pt/CNT). The device with an FTO- and Pt-free (CoS/CNT) counter electrode gives 3.13% efficiency.

More »»
2012 Journal Article J. Sun, Sun, C., Batabyal Sudip Kumar, Tran, P. D., Pramana, S. S., Wong, L. H., and Mhaisalkar, S. G., “Morphology and stoichiometry control of hierarchical CuInSe 2/SnO 2 nanostructures by directed electrochemical assembly for solar energy harvesting”, Electrochemistry Communications, vol. 15, pp. 18–21, 2012.[Abstract]

CuInSe2/SnO2 core–shell and hierarchical branched nanostructures were produced by directed electrochemical assembly. By changing the spatial electric field along the deposition region, we can control the morphology and stoichiometry of deposited product from In-poor-CuInSe2 nanoparticles to near stoichiometry CuInSe2 branched nanowires. A combination of FESEM, TEM, XRD and Raman spectroscopy investigations reveals that both morphology and chemical compositions of CuInSe2 strongly depend on the spatial electric field distribution on the SnO2/Si substrate. We observed that higher reducing potential can assist the formation of CuInSe2 with uniform coverage at the cathode side, but only In-poor-CuInSe2 nanoparticles are formed on the anode side. Optical and photo-electrochemical examination confirmed the potential application of these core–shell nanostructures for solar energy harvesting.

More »»
2012 Journal Article J. C. W. Ho, Batabyal Sudip Kumar, Pramana, S. S., Lum, J., Pham, V. T., Li, D., Xiong, Q., Tok, A. I. Y., and Wong, L. H., “Optical and electrical properties of wurtzite copper indium sulfide nanoflakes”, Materials Express, vol. 2, pp. 344–350, 2012.[Abstract]

Raman spectroscopic analysis and Hall measurement of wurtzite copper indium sulfide (CuInS2) were carried out. Nanocrystalline wurtzite CuInS2 (CIS) was synthesized by a solvothermal reaction route for these studies. It is observed that the amount of sulfur source, time and temperature of the reaction are the key to control wurtzite phase formation of CuInS2. Wurtzite nanoflakes were formed at 150 °C, with ethylenediamine as the selected solvent and the ratio of Cu:In:S precursor was kept at 1.1:1:5. The Hall measurement resulted in sheet resistivity, ρ, of ∼2 × 105 Ω/sq, Hall coefficient of ∼10 m2/C, mobility of ∼0.5 cm2/V-s and hole concentration of ∼7 × 1013/cm2. Slight shift in the Raman spectra of 1–2 cm−1 was observed between wurtzite and roquesite CuInS2 and was attributed to the stoichiometric variation in Cu/In and/or changes in the chemical environments of the two crystal structures.

More »»
2012 Journal Article K. B. Jinesh, Batabyal Sudip Kumar, R Chandra, D., and Huang, Y., “Solution-processed CuZn 1− x Al x S 2: a new memory material with tuneable electrical bistability”, Journal of Materials Chemistry, vol. 22, pp. 20149–20152, 2012.[Abstract]

CuZn1−xAlxS2 (CZAS) thin films deposited by the chemical spray pyrolysis (CSP) technique exhibit reversible electrical bistability in current–voltage measurements. The threshold voltage and current for switching can be tuned by the initial voltage applied to reset the device. X-ray diffraction and high-resolution transmission electron microscopy imaging show that the initial crystal structure of CZAS is similar to CuAlS2 with slightly expanded lattices due to the presence of Zn. The electrical memory effect in this material is observed only when both Zn and Al are present in the film, indicating that migration of interstitial Al towards the anode may be the origin of this memory effect.

More »»
2012 Journal Article A. B. Y. Lim, Batabyal Sudip Kumar, and Pramana, S., “This document is downloaded from DR-NTU, Nanyang Technological University Library, Singapore.”, 2012.
2011 Journal Article H. Kumar Mulmudi, Batabyal Sudip Kumar, Rao, M., Prabhakar, R. Ramanujam, Mathews, N., Lam, Y. Ming, and Mhaisalkar, S. Gautam, “Solution processed transition metal sulfides: application as counter electrodes in dye sensitized solar cells (DSCs)”, Phys. Chem. Chem. Phys., vol. 13, pp. 19307-19309, 2011.[Abstract]

A solution processed method for fabricating transition metal sulfides on fluorine doped tin oxide (FTO) as efficient counter electrodes in iodine/iodide based solar cells has been demonstrated. Conversion efficiencies of 7.01% and 6.50% were obtained for nickel and cobalt sulfides{,} respectively{,} comparable to the conventional thermally platinised FTO electrodes (7.32%). A comparable charge transfer resistance of Ni3S2 and Co8.4S8 to conventional Pt was found to be a key factor for such high efficiencies. Cyclic voltammetry{,} Kelvin probe microscopy{,} Electrochemical Impedance Spectroscopy{,} and Tafel polarization were performed to study the underlying reasons behind such efficient counter electrode performance. More »»
2010 Journal Article Batabyal Sudip Kumar, Leong, W. Lee, and Vittal, J. J., “Fluorescent coordination polymeric gel from tartaric acid-assisted self-assembly”, Langmuir, vol. 26, pp. 7464-7468, 2010.[Abstract]

A fluorescent organogel is obtained from the reaction of Zn(OAc)2·2H2O, 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (bpd), and tartaric acid (H4tar) in methanol. The gel is proposed to have formed by the cross-linking of linear 1D coordination polymers [Zn(bpd)]n with tartarate coligand in a highly random fashion which entrapped the solvent molecules through hydrogen-bonding interactions between the tar coligand and solvent molecules. Higher dimensional coordination polymeric structure is proposed for this gel based on the corresponding complexes formed by oxalic and succinic acids. The presence of three components is essential for the gelation. Interestingly, organogelation of the coordination polymer has induced remarkable fluorescence properties in the weakly emissive bpd. Such fluorescence enhancement is attributed to the reduction in nonradiative decay in the aggregated state. The organogel exhibits viscoelastic behavior as evidenced from the rheological studies. More »»
2010 Journal Article D. Banerjee, Chatterjee, K. R. I. S. H. A. N. U., Pal, A. B. H. I. J. I. T., Bandyopadhyay, N. R., Batabyal Sudip Kumar, Basub, C., Sanyal, G. S., and Das, A. R., “Morphology-controlled power factor of nanostructured bismuth telluride”, Fizika A-Journal of Experimental and Theoretical Physics-Zagreb, vol. 19, p. 183, 2010.
Publication Type: Patent
Year of Publication Publication Type Title
2013 Patent Y. Wai Denis Yu, Batabyal Sudip Kumar, Lev, O., Gun, J., and Prikhodchenko, P. V., “Method for forming a reduced graphene oxide/metal sulfide composite and its use as an anode for batteries”, 2013.[Abstract]

The invention relates to anode materials suitable for use in batteries, such as lithium ion batteries and sodium ion batteries. In particular, the anode material is a reduced graphene oxide/metal sulfide composite. Methods for forming the reduced graphene oxide/metal sulfide composite are also disclosed.

More »»
Publication Type: Book Chapter
Year of Publication Publication Type Title
2011 Book Chapter C. Basu, Batabyal Sudip Kumar, Das, A. R., and Sanyal, G. S., “Group V Nanostructured Chalcogenides”, in Encyclopedia of Nanoscience and Nanotechnology, vol. 15, American Scientific Publishers, 2011, pp. 37–56.


Conference presentation (Oral)

  1. Printable photovoltaic device; Keynote lecture; PARAS 2015 International Seminar on Utilization of Non-Conventional Energy Sources for Sustainable Development of Rural Areas, ISNCESR'15', 21st and 22nd March 2015, Parthivi College of Engg & Management, SIRSAKALA (Ward 33), Bhilai-3, Chhattisgarh.
  2. Metal / Metal Sulfide Nanoparticles-decorated Single-walled Carbon Nanotubes Networks as FTO-free Counter Electrodes in Dye-sensitized Solar Cells; Liling Zhang, Hemant Kumar Mulmudi, Sudip K. Batabyal, Yeng Ming Lam, Subodh Mhaisalkar; ICMAT2013 taking place from 30 June to 5 July, 2013 at SUNTEC Singapore.
  3. Metal Sulfides as Anodes for Lithium and Sodium Ion Batteries; Denis Y.W. YU, Sudip K. Batabyal, Steffen Hartung, Nicolas Bucher, Harry Hoster; ICMAT2013 taking place from 30 June to 5 July, 2013 at SUNTEC Singapore.
  4. Solution Processable CIGS (CuInGaSSe) Solar Cell; Sudip K. Batabyal; ICYRAM -2012, July 1- 6, Singapore.
  5. Coordination Polymeric Hydrogel as Novel Functional Materials; S. K. Batabyal, and J. J. Vittal; Presented as invited presentation on International Symposium on Frontiers of Functional Materials, Kolkata, India, January 6- 7, 2009.
  6. Fluorescent Coordination Polymeric Hydrogels as Novel Functional Materials; W. Leong, S. K. Batabyal and J. J. Vittal; 4th Mathematics and Physical Science Graduate Conference (MPSGC), Singapore, December 2008, oral presentation.
  7.  Electrical Bistability of Axial Junction Nanowires; S. K. Batabyal, and J. J. Vittal, Invited presentation on Frontiers Science Symposium, in National University of Singapore (NUS) November 2008.


  1. Processable Perovskite Gel Formulation For Large Area Printable Photovoltaics 
    Inventors: Sneha A. Kulkarni; Sudip Kumar Batabyal; Nripan Mathews; Subodh Mhaisalkar; Leong Wei Lin (Imre). (Applied for USA patent.)


  1. Graphene oxide gel electrolyte for quasi solid dye sensitized solar cells
    Inventors: Sudip Kumar Batabyal; Jenny Gun; Sneha A.Kulkarni; Ovadia Lev
    US Provision patent application No.- 61/772,767
  2. Coalesence Of Nanoparticles To Form Complex Materials Or Films
    Inventors: Sudip Kumar Batabyal; Lim Hui Min; Tan Jia Yi; Lydia Helena Wong; Shlomo Magdassi; Subodh Mhaisalkar
    US Provision patent application No.- 61/747,353
  3. Conversion Of Hydroperoxoantimonate Coated Graphenes To Sb2S3@Graphene For A Superior Lithium Battery Anode
    Inventors: Denis YU Yau Wai; Sudip Kumar BATABYAL; Ovadia LEV
    US Provision patent application No. 61/728,572
  4. Metal Sulfides As Anode For Na-ion Batteries
    Inventors: Denis Yu Yau Wai; Sudip Kumar Batabyal;
    US Provision patent application No. 61/814,582
  5. Singapore Patent: Processable Perovskite Gel Formulation For Large Area Printable Photovoltaics 
    Inventors: Sneha A. Kulkarni; Sudip Kumar Batabyal; Nripan Mathews; Subodh Mhaisalkar; Leong Wei Lin (Imre) (ETPL Ref: SRC/P/08659/00/SG)
  6. Singapore Patent: Semiconducting Photovoltaic Materials
    Inventors: RajivRamanujam PRABHAKAR; ZENG Xin; Sudip Kumar BATABYAL; WONG Lydia Helena; Singapore provisional application number 10201500290Y


Faculty Details


Faculty Email: