Faculty Profiles - PANDEY Shyam sudhir

Papers - PANDEY Shyam sudhir

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Computational molecular design of NIR dyes with varying anchoring groups for improving the efficiency and stability of dye-sensitized solar cells Reviewed International journal

Pandey S.S., Vats A.K., Tang L., Hayase S.

Japanese Journal of Applied Physics 61 ( SB ) SB1021-1 - SB1021-11- 2022.01

Charge transfer and catalytic properties of various PEDOTs as Pt-free counter electrodes for dye-sensitized solar cells Reviewed International journal

Yuki Kurokawa, Ajendra Kumar Vats, Takehito Kato, Suhaidi Shafie, Shyam S. Pandey

Japanese Journal of Applied Physics 61 ( SB ) SB1010-1 - SB10110-6 2022.01

Recent progress in the macroscopic orientation of semiconducting polymers by floating film transfer method, Reviewed International journal

Manish Pandey, Vipul Singh, Chandan Kumar, Shyam S. Pandey, and Masakazu Nakamura

Japanese Journal of Applied Physics 61 ( SB ) SB0801-1 - SB0801-12 2022.01

Bifacial dye-sensitized solar cells utilizing green colored NIR sensitive unsymmetrical squaraine dye Reviewed International journal

Suraya Shaban, Pritha Roy, Ajendra K. Vats and Shyam S. Pandeyy

Japanese Journal of Applied Physics 61 ( SB ) SB1005-1 - SB1005-6 2022.01

A COMPARATIVE STUDY OF GRAPHENATED-CARBON NANOTUBES COTTON AND CARBON NANOTUBES AS CATALYSTS FOR COUNTER ELECTRODE IN DYE-SENSITIZED SOLAR CELLS Reviewed International journal

Yusnita Yusuf, Suhaidi Shafie, Ismayadi Ismail, Fauzan Ahmad, Mohd Nizar Hamidon, Shyam S Pandey, Nazalea Yazmin Muhammad, Wei Lei

Malaysian Journal of Microscopy 2021.12

Language：English Publishing type：Research paper (scientific journal)

This work reports a comparative study of synthesized graphenated-carbon nanotubes cotton (g-CNTC), standard carbon nanotubes (CNTP), and conventional platinum (Pt) thin layer which are employed as the counter electrodes in dye-sensitized solar cells (DSSC). The g-CNTC was synthesized via the floating-catalyst chemical vapor deposition (FCCVD) method. Subsequently, the g-CNTC was made into a uniform paste and deposited for the counter electrode layer. The results obtained from FESEM/TEM, Raman spectroscopy, CV and I-V measurements respectively exposed the structural, graphitization and I-V characteristics. Briefly, the morphology of g-CNTC showed the growth of graphene foliates out-sidewalls of CNT with a diameter of 40 nm. The graphitization of g-CNTC showed two dominant peaks namely the D (1355 cm-1) and G (1608 cm-1) bands with strong intensities. The g-CNTC counter electrode provided good electrical conductivity (3.66×10-3 to 6.45×10-3 S/cm), which is a significant feature to employ counter electrodes to enhance DSSC performance. In addition, the g-CNTC counter electrode offered an excellent catalytic activity for iodide/triiodide reaction and exhibited 3.49 % of photovoltaic conversion energy, which was much higher compared to CNTP (2.93 %) and platinum (3.12 %), respectively.

Other Link： https://malaysianjournalofmicroscopy.org/ojs/index.php/mjm/index

Highly sensitive organic phototransistors fabricated from PCPDTBT: PCBM blend Reviewed International journal

Yadav N., Kumari N., Ando Y., Pandey S.S., Singh V.

Journal of Physics: Conference Series 2070 ( 1 ) 2021.11

Implication of color of sensitizing dyes on transparency and efficiency of transparent dye-sensitized solar cells Reviewed International journal

Roy P., Vats A.K., Tang L., Pandey S.S.

Solar Energy 225 950 - 960 2021.09

Investigation of Orientation in the Thin Films of Conjugated Polymer and NIR Dye Blends Fabricated by Friction Transfer Method Reviewed

Yuki Kurokawa, Shuichi Nagamatsu, Shyam S Pandey

IEEE Explore ( IEEE ) 2021.08

Language：English Publishing type：Research paper (international conference proceedings)

Japan Conference: 28th International Workshop on Active Matrix, Flatpanel Displays and Devices (AM-FPD21)A 2021.06.29 - 2021.07.02

Improved film's crystallinity and facile charge transport has been well demonstrated by orienting conjugated polymers using solution based thin film fabrication followed by thermal annealing, need for huge halogenated solvents and high temperature annealing are stumbling block for industrially viable large area thin film fabrication. Herein, we report the fabrication of oriented thin films regioregular P3HT by solvent-free friction transfer (FT) technique and enhancement its further enhancement by adding NIR sensitive squaraine dyes. Apart from assisting the molecular orientation of P3HT, it has been demonstrated that dye molecules are also get oriented and a synergistic match between the alkyl chains of the polymer and dye molecule leads to promotion for the extent of the molecular orientation in the dye molecules.

DOI： 10.23919/AM-FPD52126.2021.9499214

Other Link： https://ieeexplore.ieee.org/document/9499214

Extreme Orientational Uniformity in Large-Area Floating Films of Semiconducting Polymers for Their Application in Flexible Electronics Reviewed

Manish Pandey, Heriyanto Syafutra, Nikita Kumari, Shyam S. Pandey, Ryo Abe, Hiroaki Benten, and Masakazu Nakamura

ACS Applied Materials & Interfaces ( American Chemical Society ) 2021.08

Language：English Publishing type：Research paper (scientific journal)

Layer-by-layer fabrication of uniformly oriented thin films over large areas by cost-effective solution-based approaches can open new horizons for the realization of high-performance organic circuits in various applications. In this work, fabrication of a large-area ≈40 cm2 film with uniform orientation is reported for poly(3,3‴-dialkylquaterthiophene) (PQT) using a unidirectional floating film transfer method (UFTM). Orientation characteristics and charge transport anisotropy were analyzed using polarized UV–vis spectral mapping and fabrication of bottom-gated organic field-effect transistors (OFETs) from different regions. Films were found to be highly oriented with an optical dichroic ratio of ca. 15. Orientation characteristics reveal that films were highly oriented along the width of the film, covering >70% of the area, and angle-dependent field-effect mobilities are in good agreement with the orientation of the polymer backbones. These highly oriented films resulted in charge transport anisotropy of 8.9. An array of bottom-gated OFETs fabricated along the length of single large-area (≈15 × 2.5 cm2) thin film demonstrated the average field-effect mobility of 0.0262 cm2/(V s) with a very narrow standard deviation of 12.6%. We also demonstrated that film thickness can be easily tuned from 5.6 to 45 nm by increasing the PQT concentration, and field-effect mobility is highly reproducible even when the film thickness is 10 nm. Microstructural characterization of the thus-prepared large-area thin films revealed the edge-on stacked polymer backbones and surface roughness of <1 nm as probed by grazing incidence X-ray diffraction and atomic force microscopy, respectively. Flexible OFETs with bottom-gate top-contact geometry were also fabricated, having average field-effect mobility of 0.0181 cm2/(V s). There was no considerable change in mobility after bending the flexible devices at different radii.

DOI： 10.1021/acsami.1c09671

Other Link： https://pubs.acs.org/doi/abs/10.1021/acsami.1c09671

Assisted alignment of conjugated polymers in floating film transfer method using polymer blend Reviewed

Heriyanto Syafutra, Manish Pandey, Nikita Kumari, Shyam S Pandey, Hiroaki Benten, Masakazu Nakamura

Thin Solid Films ( Elsevier ) 734 138814(1) - 138814(8 2021.07

Language：English Publishing type：Research paper (scientific journal)

Orientating conjugated polymers (CPs) in thin films is an attractive technique for obtaining anisotropic properties, resulting in improved device performances. Template-assisted alignment using pre-patterned substrates has been widely used to orient various polymers irrespective of their orientation capability. In this work, we report that using the floating film transfer method, the orientation of guest polymers can be in-situ assisted via blending with a host polymer during film fabrication. Dichroic Ratio (DR) of two guest CPs such as poly[2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5-(2,5-di(thien-2-yl)thieno[3,2-b]thiophene)] and poly(9,9-di-n-octylfluorenyl-2,7-diyl) were found to be enhanced when blended with host polymer poly(3,3‴-didodecyl-quaterthiophene) (PQT). DR of the host PQT decreases monotonically with an increase in the guest polymer proportion, suggesting that guest polymers are well mixed in the host matrix. The electronic absorption spectra and atomic force microscopy results revealed that blended polymers were well mixed without any phase separation. DR of the guest polymers in the blend was the same even when the overall blend concentration was increased twice to increase the overall film thickness.

DOI： 10.1016/j.tsf.2021.138814

Other Link： https://www.sciencedirect.com/science/article/pii/S0040609021002972

Development of High-Sensitivity Poly (2, 7-(9, 9-dioctylfluorene)-alt-5, 5-(4', 7'-di-2-thienylbenzo [c][1, 2, 5] thiadiazole)) Thin-Film-Based Phototransistors by the Ribbon-Floating Film Transfer Method Reviewed International journal

Nidhi Yadav, Nikita Kumari, Yoshito Ando, Shyam S. Pandey, and Vipul Singh

Physica Status Solidi (RRL) - Rapid Research Letters ( WILEY-V CH VERLAG GMBH ) 2021.06

Language：English Publishing type：Research paper (scientific journal)

Alignment of polymer chains hold key to development of highly functional polymer based field effect transistors. Our recently developed ribbon-floating film transfer method (ribbon-FTM) has the potential for development of polymer thin films with highly aligned chains which are desirable for fabrication of efficient planar devices. These thin films consisting of well aligned polymer chains exhibit high degree of optical and electronic anisotropies. In this work we report ribbon-FTM processed thin film based organic photosensitive transistors of PFO-DBT. Under optimized fabrication conditions polymer FETs based on PFO-DBT demonstrated a charge carrier mobility of 0.002 cm²/Vs and an on-off ratio of 5 × 10⁴ under dark conditions. The devices have further demonstrated a Photosensitivity of ∽10⁴ and 10³ and a high Responsivity of 8.37 A/W and 4.6 A/W against green and red light illuminations, respectively. The results hold promise for development of conducting polymer based high performance photosensitive OFETs. This article is protected by copyright. All rights reserved.

DOI： 10.1002/pssr.202100185

Other Link： https://onlinelibrary.wiley.com/doi/epdf/10.1002/pssr.202100185

Probing the metal/conducting polymer interface and implications of the metal diffusion in two-terminal sandwich devices Reviewed International journal

Nidhi Yadav, Nikita Kumari, Yoshito Ando, Shyam S Pandey, Vipul Singh

Synthetic Metals ( Synthetic Metals ) 278 116797(1) - 116797(11) 2021.05

Language：English Publishing type：Research paper (scientific journal)

In this article, we have investigated the role of polymer regio-regularity and film fabrication technique in reducing metal diffusion from top electrodes in sandwich type devices. Poly(3-hexyl thiophene)(P3HT) polymer of varying regio-regularity was chosen for investigation and its corresponding thin films were fabricated by spin-coating(SC) and floating film transfer method(FTM). Sandwich devices with a top interface between gold and i) FTM coated regio-regular (rr) P3HT, ii) FTM coated non-regiocontrolled (nr) P3HT, iii) SC nr-P3HT and iv) SC rr-P3HT were fabricated. The current density vs voltage (J-V) characteristics of the devices revealed non-ohmic characteristics. Estimation of interfacial hole barrier heights using Fowler Nordheim tunneling model revealed a small barrier of 1.12 eV for the isotropic spin-coated nr-P3HT film which increased to 1.37 eV with an increase in film anisotropy for the FTM nr-P3HT film. The barrier height also gradually declined from 1.37 eV to 1.05 eV with increase in regioregularity from FTM nr-P3HT to FTM rr-P3HT. These observations were confirmed through optical and structural characterizations along with depth profiling of metal diffusion using XPS. Pronounced Au diffusion to a higher depth was observed in the XPS results for the highly anisotropic FTM film that decreased subsequently with decrease in anisotropy from FTM to spin-coated film. It was thus deduced that a judicious selection of fabrication technique and polymer aids in reducing metal diffusion leading to improved device performance. The results hold crucial significance towards the fabrication of efficient organic photodetectors that have a sandwich type device architecture.

DOI： 10.1016/j.synthmet.2021.116797

Other Link： https://www.sciencedirect.com/science/article/pii/S0379677921001028

Development of PCPDTBT thin film based highly sensitive organic phototransistors Reviewed International journal

Nidhi Yadav, Nikita Kumari, Shyam S Pandey, Vipul Singh

Materials Today' Proceeding ( Elsevier ) 2021.04

Language：English Publishing type：Research paper (international conference proceedings)

In this report, we have proposed a novel ribbon-FTM method to develop highly oriented polymer thin films. A donor–acceptor (D-A) type copolymer, PCPDTBT has been selected as the target material for investigation. The maximally oriented film showcased a DR of 4.1. Highly aligned polymer film was used as the active layer for the development of bottom gate bottom contact (BGBC) type OFETs. An average mobility and an Ion/Ioff of 0.002 cm2/Vs and 5 × 103 were obtained under dark conditions, respectively. Upon illumination with monochromatic green light (λ = 522 nm, Pin = 0.5 mW/cm2), the OPTs showcased a high photosensitivity and responsivity of 103 and 17 A/W, respectively. The obtained values were found to be superior over many of the previously reported similar OPTs which employed other organic polymers. The results thus are of crucial significance with respect to the development of facile, cost effective and highly sensitive single polymer thin film based OPTs.

DOI： 10.1016/j.matpr.2021.03.468

Other Link： https://www.sciencedirect.com/science/article/pii/S2214785321025232?via%3Dihub

Fatigue life prediction of electroactive polymer strain sensor Reviewed

Nitin Kumar Singh, Kazuto Takashima, Shyam Sudhir Pandey

Electroactive Polymer Actuators and Devices (EAPAD) XXIII ( International Society for Optics and Photonics ) 11587 115871Z(1) - 115871Z(7) 2021.03

Language：English Publishing type：Research paper (international conference proceedings)

USA Sandiego, California 2021.03.22 - 2021.03.27

Electroactive polymers strain sensors bear a great potentiality in the area of soft robotics, wearable devices, and fitness industries. A small initial defect present in such sensor may grow to a critical size during contraction and relaxation cycles leading to mechanical failure, therefore, prediction of fatigue life is inevitable. The crack growth approach is one of the amicable ways to estimate the fatigue life considering parameters like tear energy, crack geometry, and power law. In this work, crack growth approach based on power law is being proposed to predict fatigue life utilizing conducting and stretchable freestanding films consisted of SEBS rubber and dodecyl benzenesulfonic acid (DBSA) doped polyaniline composite. Utilizing this crack growth model for the prediction of fatigue life exhibited that such films can sustain more than a million cycles even at a large value of deformation.

DOI： 10.1117/12.2584521

Other Link： https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11587/115871Z/Fatigue-life-prediction-of-electroactive-polymer-strain-sensor/10.1117/12.2584521.short

PCPDTBT copolymer based high performance organic phototransistors utilizing improved chain alignment Reviewed International journal

Nidhi Yadav, Nikita Kumari, Yoshito Ando, Shyam S Pandey, Vipul Singh

Optical Materials ( Elsevier ) 113 110886(1) - 110886(9) 2021.03

Language：English Publishing type：Research paper (scientific journal)

In this article, we report single component thin film based organic phototransistors (OPTs) developed using the novel ribbon-floating film transfer method (ribbon-FTM). A low band-gap copolymer, poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) has been employed to develop the photoactive thin films of the devices. The fabricated polymer films were highly anisotropic in nature. To investigate the effect of film anisotropy on the device performance, organic field effect transistors (OFETs) were fabricated in two configurations namely, parallel and perpendicular, wherein the polymeric chains were oriented in line and orthogonal to the transistor channel direction, respectively. Notable differences in charge carrier mobility and device on-off ratios were observed among the two sets of devices. An on-off ratio of 4.1 × 103 and an average mobility of 0.001 cm2/V were observed in case of the perpendicular oriented OFETs which were increased to 105 and 0.003 cm2/V for the parallel oriented OFETs. A probe into the contact resistance at the respective metal/polymer interfaces of the devices was carried out using the modified transmission line method (MTLM). 4 times lower contact resistance was observed in the parallel OFET which was anticipated to be responsible for its superior performance. Further, the fabricated devices were illuminated with monochromatic red light (Pin = 0.4 mW/cm2) to observe their performance as phototransistors. Appreciable values of photosensitivity (2 × 104) and photoresponsivity (17.6 A/W) were obtained for the parallel OPTs which were found to be much higher than those of the previously reported thin film based OPTs employing other materials fabricated through conventional film coating techniques. The results presented in this report are of key significance towards the development of highly sensitive and cost-effective phototransistors which can be used in opto-sensing and imaging applications.

DOI： 10.1016/j.optmat.2021.110886

Other Link： https://www.sciencedirect.com/science/article/pii/S0925346721000872

Unravelling the bottleneck of phosphonic acid anchoring groups aiming toward enhancing the stability and efficiency of mesoscopic solar cells Reviewed International journal

Vats A.K., Roy P., Tang L., Hayase S., Pandey S.S.

Frontiers of Chemical Science and Engineering 16 ( 7 ) 1060 - 1078 2021.01

Investigation of Orientation in the Thin Films of Conjngated Polymer and NIR Dye Blends Fabricated by Friction Transfer Method Reviewed International journal

Kurokawa Y., Nagamatsu S., Pandey S.S.

Proceedings of AM-FPD 2021 - 28th International Workshop on Active-Matrix Flatpanel Displays and Devices: TFT Technologies and FPD Materials 96 - 99 2021.01

Solvent-Assisted Friction Transfer Method for Fabricating Large-Area Thin Films of Semiconducting Polymers with Edge-On Oriented Extended Backbones Reviewed

Kumari N., Pandey M., Syafutra H., Nagamatsu S., Nakamura M., Pandey S.S.

ACS Applied Materials and Interfaces 12 ( 49 ) 55033 - 55043 2020.12

Language：English Publishing type：Research paper (scientific journal)

© Recent past has witnessed huge scientific efforts aiming toward enhancing in-plane charge transport by unidirectional orientation of conjugated polymer (CP) backbones adopting various techniques. However, in most of the existing methods, excess amounts of toxic halogenated solvents and preaggregation in solution are inevitable, which are the main bottlenecks toward large-scale fabrication. Solvent-assisted friction transfer (SAFT) is being reported as a novel method and improvisation over conventional friction transfer to expand its versatility. In this method, application of a small amount of the solvent (∼3 μL) during drawing not only leads to the entirely changed film morphology and molecular orientation but also addresses the existing substrate compatibility issues. Utilizing poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]-thiophene] as a representative CP under SAFT technique, films with extended backbone and edge-on orientation was successfully fabricated, which was confirmed by various characterization tools such as X-ray diffraction, polarized absorption, and polarized Raman spectroscopies. Further, anisotropic charge transport in these films was investigated by fabricating organic field-effect transistors and the role of contact resistance was also studied. Slight solvent use, compatibility with various substrates, and film fabrication with controlled orientation, and after validation of its generality on different CPs, SAFT can be expected to open new avenues in the area of printed electronics.

DOI： 10.1021/acsami.0c14874

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85097812392&origin=inward

Comprehensive performance analysis of dye-sensitized solar cells using single layer TiO<inf>2</inf> photoanode deposited using screen printing technique Reviewed

Khalifa A., Shafie S., Hasan W.Z.W., Lim H.N., Rusop M., Pandey S.S., Vats A.K., AlSultan H.A., Samaila B.

Optik 223 2020.12

Language：English Publishing type：Research paper (scientific journal)

© 2020 Elsevier GmbH A single-layer N719 sensitized nanocrystalline TiO2 films have been successfully deposited on FTO-coated glass substrates using the screen-printing technique with four different thicknesses (10, 12, 14 and 18 μm) and used as simple and low cost photoanodes for dye-sensitized solar cells (DSSCs). The thickness was controlled by adjusting the distance between the screen-printing mesh and the FTO-coated substrate using the two height control bolts. The films were deposited using one-time screen-printing method. So that the multiple screen-printing and annealing cycles can be reduced. Furthermore, the cell fabrication time was reduced as well as the problem of recombination at the interfacial layers between the TiO2 films was avoided. The thickness of the TiO2 films was measured by the surface profilometer. The prepared photoanode samples were characterized using FESEM, EDX, AFM, and UV–vis-NIR spectroscopies. The ruthenium dye soaking time was optimized at 48 h. The photovoltaic parameters such as short circuit current density (Isc), open-circuit voltage (Voc), fill factor (FF) and power conversion efficiency (η) were measured for fabricated cells at room temperature under one sunlight 100 mW/cm2 illumination using the solar simulator. The effect of TiO2 film thickness on the fabricated DSSCs performance parameters was studied. DSSC devices with average thickness 12μm achieved the highest conversion efficiency of 5.13 % with Jsc = 12.12 mA/cm2, and Voc = 0.69 V. The obtained results revealed that the amount of the adsorbed dye increases with the increase in the TiO2 film thickness and thus improve photogenerated current. However, exceeding the optimum photoanode thickness results in decline in the photogenerated current and the overall efficiency due to back electrons recombination and the lower photoanode transmittance.

DOI： 10.1016/j.ijleo.2020.165595

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85091226691&origin=inward

Ordered arrangement of F4TCNQ anions in three-dimensionally oriented P3HT thin films Reviewed

Nagamatsu S., Pandey S.S.

Scientific Reports 10 ( 1 ) 2020.12

Language：English Publishing type：Research paper (scientific journal)

© 2020, The Author(s). An ordered arrangement of electron-accepting molecular dopant, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), in three-dimensionally (3D) oriented poly(3-hexylthiophene) (P3HT) film was clarified. The 3D oriented P3HT thin films prepared by the friction-transfer technique were doped with F4TCNQ by dipping into an acetonitrile solution. The presence of F4TCNQ anions in the 3D oriented P3HT thin films was investigated by polarized ultraviolet/visible/near-infrared absorption spectroscopy, grazing incidence X-ray diffractometry, polarized Fourier transform infrared spectroscopy (FT-IR), and infrared p-polarized multiple-angle incidence resolution spectroscopy (pMAIRS). The F4TCNQ-doped 3D oriented P3HT films showed anisotropic properties in all characterizations. In particular, the anisotropic molecular vibrations from polarized FT-IR and pMAIRS have clearly revealed orientations of polymeric chains and molecular dopant molecules. Considering the results from several independent techniques indicated that F4TCNQ anions in the 3D oriented P3HT were orderly arranged in a 3D manner with respect to the 3D oriented P3HT such that their molecular long-axis parallel to the P3HT backbone, with in-plane molecular orientation. Additionally, the direction of the optical transition moment of the F4TCNQ anion was found to be parallel to the molecular short-axis.

DOI： 10.1038/s41598-020-77022-0

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85096179925&origin=inward

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Papers - PANDEY Shyam sudhir