Faculty Profiles - PANDEY Shyam sudhir

Papers - PANDEY Shyam sudhir

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Effect of electrolyte for back contact transparent conducting oxide-less dye-sensitized solar cells: Iodine versus cobalt Reviewed

Molla M.Z., Baranwal A.K., Hayase S., Pandey S.S.

Journal of Photonics for Energy 10 ( 4 ) 2020.10

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

© 2020 Society of Photo-Optical Instrumentation Engineers (SPIE). Grätzel solar cells are reported in a transparent conducting oxide-less (TCO-less) back-contact dye-sensitized solar cell (BC-DSC) architecture using a stainless steel mesh-protected working electrode along with nanoporous TiO2 semiconductor and metal-free D205 dye. Liquid electrolytes play a significant role for the dye regeneration in the working operation of TCO-less BC-DSCs; therefore, we report the effectiveness of two different commonly utilized electrolytes (iodine-and cobalt-based redox shuttles) for the construction and performance of TCO-less dye-sensitized solar cells (DSCs). Differential performance of DSCs thus fabricated was interpreted utilizing impedance spectral and lifetime analysis. It was found that although utilization of cobalt bipyridyl complex-based electrolyte was able to harvest higher photons in the lower wavelength region (330 to 430 nm) as compared to its iodine electrolyte counterparts, hampered dye regeneration due to reduced driving force and slower ion diffusion in combination with higher charge transport resistance at TiO2 / dye / electrolyte was responsible for relatively hampered photovoltaic performance at peak absorption.

DOI： 10.1117/1.JPE.10.045501

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Boosting the Efficiency of Low-Cost T-C-O-Less Dye-Sensitized Solar Cells Employing Nanoparticle Spacers and Cobalt Complex Redox Shuttle Reviewed

Molla M.Z., Baranwal A.K., Hayase S., Pandey S.S.

ACS Applied Electronic Materials 2 ( 9 ) 2721 - 2729 2020.09

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

© 2020 American Chemical Society. A strategy has been explored to enhance the diffusion of Co2+/3+ species through the dye-stained nanoparticle spacer employed as an electrolyte absorbing layer with different nanoparticle sizes of TiO2 (30 and 20 nm) and ZrO2 (15 nm) films in transparent conducting oxide-less back-contact dye-sensitized solar cells (T-C-O-less B-C-DSCs). A dye-stained nanoparticle spacer with a relatively larger particle of the TiO2 (30 nm) film brought about easy diffusion of cobalt(II/III) complexes leading to an enhanced photoconversion efficiency (PCE) of 6.55% as compared to relatively smaller nanoparticle of the TiO2 (20 nm) film (4.95%) and ZrO2 (15 nm) film (2.03%). The T-C-O-less B-C-DSC exhibits a lower PCE of 6.55% relative to the T-C-O-based DSC (9.10%) owing to relatively hampered diffusivity of [Co(bpy)3]3+/2+ complexes through perforated holes of the SS-mesh as well as the nanoparticle spacer. A differential study reveals that the cobalt electrolyte exhibits much improved light accumulation in the range 330-430 nm relative to the iodine electrolyte counterpart. The corrosion study of the SS-mesh and Ti-protected SS-mesh reveals that stable T-C-O-less B-C-DSCs can be attained only by the cobalt electrolyte because of its mild nature toward the SS-mesh and Ti metal as compared to the iodine electrolyte.

DOI： 10.1021/acsaelm.0c00437

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Parametric optimization of back-contact T-C-O-free dye-sensitized solar cells employing indoline and porphyrin sensitizer based on cobalt redox electrolyte Reviewed

Molla M.Z., Baranwal A.K., Kapil G., Hayase S., Pandey S.S.

Solar Energy 208 411 - 418 2020.09

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

© 2020 International Solar Energy Society Transparent-conductive-oxide-free (T-C-O-free) back-contact (B-C) dye-sensitized solar cell (DSC) utilizing flexible Stainless Steel (SS) mesh (SS-mesh) supported with mesoporous TiO2 as a photoanode employing cobalt electrolyte is being presented. A thin layer of Ti metal over the SS-mesh was ascertained to be essential to retard the back electron reaction, which was confirmed by the dark current measurements. The interfacial contact between the SS-mesh and nanoporous (NP) TiO2 of the photoanode of T-C-O-free B-C-DSC was driven to influence the photovoltaic performance greatly. It was confirmed by electrochemical impedance analysis that NP TiO2 of 30 nm exhibited less charge transfer impedance observed at TiO2-dye-electrolyte interface as compared to TiO2 of having particle size of 15–20 nm. T-C-O-free B-C-DSC employing dye mixer combination of indoline dyes D-131 and D-205 (1:1) with relatively larger NP of TiO2 (30 nm) as compared to TiO2 of 15–20 nm exhibited enhanced photoconversion efficiency (PCE) of 4.02%. To increase the PCE even further, T-C-O-free B-C-DSC with cobalt based electrolyte sensitized with porphyrin (YD2-o-C8)-dye bearing a larger optical window was investigated. An optimized 10 µm thickness of the TiO2 layer was found to be optimum leading to an enhanced PCE of 5.26%.

DOI： 10.1016/j.solener.2020.08.011

Scopus

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Stability Improvement of Perovskite Solar Cells by Adding Sb-Xanthate to Precursor Solution Reviewed

Nam K.S., Krishnamurthy S., Qing S., Toyoda T., Yoshino K., Minemoto T., Ma T., Pandey S., Hayase S.

Physica Status Solidi (A) Applications and Materials Science 217 ( 18 ) 2020.09

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

© 2020 Wiley-VCH GmbH Herein, it is reported that the stability of a halogenated perovskite (PVK) solar cell consisting of an fluorine-doped tin oxide (FTO) substrate/TiO2/CH3NH3PbI3/N2,N2,N2′,N2′,N7,N7,N7′,N7′-octakis(4-methoxyphenyl)-9,9′-spirobi[9H-fluorene]-2,2′,7,7′-tetramine/Ag/Au structure is improved by adding Sb-xanthate to the PVK layer without large loss of efficiency. The Sb-element-rich layer is observed on top of the PVK layer. From the X-ray photoelectron spectroscopy (XPS) study, it is concluded that an inorganic SbxOy passivation layer on the PVK layer is prepared by baking the solution of the Sb-xanthate and the PVK precursor. The inorganic layer prevents moisture and oxygen from penetrating into the PVK layer. This article provides a new method to obtain a passivation layer on a PVK layer by baking a mixture solution in one step for improving solar cell stability.

DOI： 10.1002/pssa.202000144

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Reduced contact resistance in organic field-effect transistors fabricated using floating film transfer method Reviewed

Bhargava K., Yadav N., Kumari N., Pandey S.S., Singh V.

Journal of Materials Science: Materials in Electronics 31 ( 18 ) 15277 - 15285 2020.09

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

© 2020, Springer Science+Business Media, LLC, part of Springer Nature. This paper presents an in-depth performance-based comparison of organic field-effect transistors (OFETs) prepared using the conventional spin coating (SC) technique and a recently developed floating film transfer method (FTM). A remarkable improvement in the performance of transistors fabricated using FTM was achieved in comparison to their SC counterparts. The estimated value of width-normalized contact resistance in FTM-based OFETs was an order lower in comparison to that of transistors prepared using SC technique. The observed results were credited to a significant enhancement in the length of π-conjugation due to the presence of edge-on oriented polymer chains of active layer deposited using FTM, leading to the lowering of carrier injection barrier at the Au/P3HT interface. These results were well supported through absorption, photoluminescence and Raman measurements as well as the anisotropy measurements using polarized absorption spectra, which also pointed towards the improvement in the polymer chain alignment of thin films prepared by FTM over that prepared by the conventional SC technique. The results indicate thin film morphology as a key towards reducing the contact resistance in OFETs.

DOI： 10.1007/s10854-020-04092-1

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Orientation of Semiconducting Polymers via Swift Printing and Drawing Techniques for High Performance Organic Electronic Devices Reviewed

Kumari N., Sharma S., Nagamatsu S., Pandey S.S.

Proceedings of AM-FPD 2020 - 27th International Workshop on Active-Matrix Flatpanel Displays and Devices: TFT Technologies and FPD Materials 67 - 70 2020.09

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

© 2020 FTFMD. Recent developments in the field of organic electronics are being triggered by various approaches aiming towards enhancing the charge transport in thin-films of processable organic semiconductors such as novel molecular design, synthesis and increasing their crystallinity and molecular orientation adopting various thin film fabrication techniques. However, intriguing challenges associated with serious health and environment hazards due to inevitable use of halogenated solvents are needed to be addressed amicably before the practical realization of organic electronic devices. In order to address this issue, thin film fabrication techniques like floating-film transfer and friction transfer have been utilized to demonstrate environment friendly and sustainable fabrication of large area thin-films possessing adequate uniformity without comprising the facile charge transport. Organic field effect transistors were fabricated using different regions of the large-area thin films (≥ 10 cm2) and by optimizing casting conditions, uniformity in the field effect mobility (μ) was demonstrated. Besides this, as compared to most commonly used spin coating, one order of magnitude enhancement in the μ was successfully achieved utilizing oriented thin films fabricated by our methods.

DOI： 10.23919/AM-FPD49417.2020.9224472

Kyutacar

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Comparative analysis of metal diffusion effects in polymer films coated with spin coating and floating film transfer techniques Reviewed

Yadav N., Bhargava K., Kumari N., Pandey S.S., Singh V.

Synthetic Metals 264 2020.06

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

© 2020 Elsevier B.V. In this work a comparative analysis between the extent of gold diffusion of the top coated gold layer into the conducting polymer matrix of spin coated polymer films and polymer films coated via floating film transfer method (FTM) has been investigated. For the sake of comparison two different device configurations i.e. ITO/rr-P3HT (spin coated)/Au and ITO/rr-P3HT (spin coated)/rr-P3HT (FTM coated)/Au have been compared. The J-V characteristics of these devices revealed a non-Ohmic injection occurring near the top gold electrode/polymer interface. Furthermore, the current flowing through the device consisting of FTM layer/Au interface was observed to be lower as compared to the one consisting of spin coated layer/Au interface, indicating higher gold diffusion in well-ordered FTM thin films. These observations have been validated by optical and structural characterization methods viz. absorption, photoluminescence, Raman spectroscopy and X-Ray Diffraction (XRD) measurement. Finally Fowler-Nordheim (FN) tunneling currents were studied under high electric field applications for the two devices which confirmed presence of higher barrier at the interface of gold and FTM coated polymer film.

DOI： 10.1016/j.synthmet.2020.116378

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Synthesis, Photophysical characterization and dye adsorption behavior in unsymmetrical squaraine dyes with varying anchoring groups Reviewed

Ajendra Kumar Vats, Anusha Pradhan, Shuzi, Hayase, Shyam S. Pandey

Journal of Photochemistry and Photobiology A: Chemistry ( Elsevier ) 394 112467(1) - 112467(12) 2020.03

Molecular Orientation and Anisotropic Charge Transport in the Large Area Thin Films of Regioregular Poly (3-alkylthiopnes) Fabricated by Ribbon-Shaped FTM Reviewed

Atul SM Tripathi, Rakesh Kumar Gupta, Shubham Sharma, Shuichi Nagamatsu, Shyam S Pandey

Organic Electronics ( Elsevier ) 81 105683(1) - 105683(9) 2020.03

Investigation and control of charge transport anisotropy in highly oriented friction transferred polythiophene thin films Reviewed

Nikita Kumari, Manish Pandey, Shuichi Nagamatsu, Masakazu Nakamura, Shyam Sudhir Pandey

ACS Applied Materials & Interfaces ( American Chemical Society ) 12 ( 10 ) 11876 - 11883 2020.02

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)

Highly oriented thin films of poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT) were prepared by friction-transfer technique followed by their characterization using polarized absorption spectroscopy, angle-dependent polarized Raman spectroscopy, and X-ray diffraction (XRD) techniques. Orientation in high-molecular-weight (MW) polymers is hampered by chain folding or entanglements, which limit their macromolecular orientation. Interestingly, utilizing high-molecular-weight PBTTT (MW > 50 kDa) and friction-transfer technique, successful fabrication of highly oriented thin films with very high dichroic ratio (∼30) was demonstrated. The role of the substrate's surface energy and its impact on the field-effect mobility (μ) of the oriented thin films were comprehensively investigated. The influence of annealing the thin films as prepared on the bare and self-assembled monolayer (SAM)-treated SiO2 surfaces exhibiting differential trends of μ was systematically investigated. This was explained by partial and complete conformational transformation of macromolecules on bare and SAM-treated SiO2 surfaces, respectively, after annealing them beyond liquid crystalline phase transition temperature, as revealed by in-plane and out-of-plane XRD results. On bare SiO2, optimum μ up to 0.03 cm2 V–1 s–1 along the backbone orientation was obtained for the thin films annealed to 120 °C; whereas, it reached up to 0.36 cm2 V–1 s–1 on SAM-treated SiO2 after annealing at 200 °C. Finally, a charge transport mechanism was proposed taking evidence from the anisotropic optical and electrical characteristics of the friction-transferred PBTTT films into consideration.

DOI： 10.1021/acsami.9b23345

Kyutacar

Other Link： https://pubs.acs.org/doi/abs/10.1021/acsami.9b23345

2D positional mapping of casting condition driven microstructural distribution in organic thin films Reviewed

Kumari N., Pandey M., Nagamatsu S., Pandey S.S.

Japanese Journal of Applied Physics 59 ( SC ) 2020.02

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

© 2019 The Japan Society of Applied Physics. Fabrication of large-area thin films and their swift characterization is highly desired for the commercial aspects of the organic electronic devices. Although a number of techniques have been proposed for the large-area thin film fabrication, the microstructural variation is still an issue. In this work, the facile characterization of distribution in thickness and macromolecular ordering in the drop-casted and spin-coated poly(3-hexylthiophene) thin films have been performed through newly developed 2D positional mapping technique. Through this technique, a comparative analysis of the absorption spectra in terms of peak absorbance and excitonic bandwidth (W) was performed for the whole sample, the lower value of W observed for the drop-casted thin film depicts its molecular ordering. Moreover, the difference in W (≈ 10 meV) was noticed between two points (≈1 mm apart) on the drop-casted film, which corresponds to the difference in microstructural ordering and it is complicated to characterize through the conventional spectroscopic techniques.

DOI： 10.7567/1347-4065/ab48b9

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2D positional mapping of casting condition driven microstructural distribution in organic thin films Reviewed

Nikita Kumari, Manish Pandey, Shuichi Nagamatsu, Shyam S Pandey

Japanese Journal of Applied Physics ( IOP Science ) 69 ( SC ) SCCA06-1 - SCCA06-6 2019.11

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)

Fabrication of large-area thin films and their swift characterization is highly desired for the commercial aspects of the organic electronic devices. Although a number of techniques have been proposed for the large-area thin film fabrication, the microstructural variation is still an issue. In this work, the facile characterization of distribution in thickness and macromolecular ordering in the drop-casted and spin-coated poly(3-hexylthiophene) thin films have been performed through newly developed 2D positional mapping technique. Through this technique, a comparative analysis of the absorption spectra in terms of peak absorbance and excitonic bandwidth (W) was performed for the whole sample, the lower value of W observed for the drop-casted thin film depicts its molecular ordering. Moreover, the difference in W (≈ 10 meV) was noticed between two points (≈1 mm apart) on the drop-casted film, which corresponds to the difference in microstructural ordering and it is complicated to characterize through the conventional spectroscopic techniques.

Kyutacar

Other Link： https://iopscience.iop.org/article/10.7567/1347-4065/ab48b9/meta

P3HT Nanofibrils Thin-Film Transistors by Adsorbing Deposition in Suspension Reviewed

Shuichi Nagamatsu, Masataka Ishida, Shougo Miyajima, Shyam S Pandey

Materials ( MDPI ) 12 ( 21 ) 3643 2019.11

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

A novel film preparation method utilizing polymer suspension, entitled adsorbing deposition in suspensions (ADS), has been proposed. The poly(3-hexylthiophene) (P3HT) toluene solution forms P3HT nanofibrils dispersed suspension by aging. P3HT nanofibrils are highly crystallized with sharp vibronic absorption spectra. By the ADS method, only P3HT nanofibrils in suspension can be deposited on the substrate surface without any disordered fraction from the dissolved P3HT in suspension. Formed ADS film contains only the nanostructured conjugated polymer. Fabricated polymer thin-film transistor (TFT) utilizing ADS P3HT film shows good TFT performances with low off current, narrow subthreshold swing and large on/off current ratio

DOI： 10.3390/ma12213643

Other Link： https://www.mdpi.com/1996-1944/12/21/3643

Clitoria ternatea flower as natural dyes for Dye-sensitized solar cells Reviewed

Azwar Hayat, A Erwin E Putra, Novriany Amaliyah, Shyam S Pandey

IOP Conference Series: Materials Science and Engineering ( IOP Science ) 619 ( 1 ) 012049-1 - 012049-6 2019.10

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

Clitoria ternatea flowers have been investigated as a natural sensitizer in Dye-sensitized solar cell (DSSC). Dried C. ternatea flowers ware immersed in ethanol for 48 hours in dark room to obtain anthocyanin pigments. We compared the photovoltaic performance of the sensitizers with Titanium dioxide (TiO2) only and TiO2 with scattering layers. C. ternatea dyes have higher Power Conversion Efficiency (PCE) when applied in TiO2 with scattering layers compared to standard TiO2 semiconductors. Scattering layer (SL) has increased the light path inside the photo-anode film that doubled the short-circuit current (Jsc) and enhanced the open circuit voltage (Voc) compared to TiO2 based cell without the SL. In conclusion, from the result, higher electron injections can be achieved by light management on photo-anode film with scattering layers as one of strategy to enhance the efficiency for further low cost and environment-friendly solar cell.

Kyutacar

Other Link： https://iopscience.iop.org/article/10.1088/1757-899X/619/1/012049/meta

Role of device architecture and AlOX interlayer in organic Schottky diodes and their interpretation by analytical modeling Reviewed

Nikita Kumari, Manish Pandey, Kengo Hamada, Daisuke Hirotani, Shuichi Nagamatsu, Shuzi Hayase, Shyam S Pandey

Journal of Applied Physics ( American Institute of Physics ) 126 125501-1 - 125501-12 2019.09

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)

Considering the pivotal role of interfaces in controlling the performance of organic electronic devices, implications of metal/organic interfacial quality in a Schottky barrier diode (SBD) are investigated. The nature of metal/organic interfaces and the thin film quality of regioregular poly (3-hexylthiophene) based SBDs fabricated in different device architectures are investigated using experimental and theoretical modeling. The importance of oxidized aluminum nanostructures as an interlayer at the Schottky interface for the dramatic enhancement of the rectification ratio (>106 at ±5 V) has been demonstrated, which is attributed to suppressed leakage current due to the oxide layer and the formation of a charge double layer. Furthermore, electrical performances of all the SBDs were modeled in terms of an underlying particular phenomenon solely or with the combination of multiple physical phenomena. The combined modeling equation used in this work fits well for the different device architectures, which validates its generality in order to extract the device parameters

DOI： 10.1063/1.5109083

Other Link： https://aip.scitation.org/doi/full/10.1063/1.5109083

Recent advances in the orientation of conjugated polymers for organic field-effect transistors Reviewed

Manish Pandey, Nikita Kumari, Shuichi Nagamatsu, Shyam S Pandey

Journal of Materials Chemistry ( Royal Society of Chemistry ) 7 13323 - 13351 2019.09

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)

Solution processable conjugated polymers (CPs) possess unique molecular structures in terms of extended π-conjugation in combination with quasi 1-dimensionality, imparting them with an inherent tendency for molecular self-assembly and ultimately determining their optoelectronic properties. Short-range molecular ordering and long-range macroscopic orientation are two different but interdependent phenomena, which should be optimized depending on the nature of electronic devices (planar versus vertical). Judicious control of the macromolecular orientations and conformation-assisted morphologies of CPs are key for determining and controlling the anisotropic charge transport in organic field effect transistors (OFETs). The present review focuses on different solution-based approaches for thin film fabrication developed in the last two decades aimed towards controlling the film morphologies and macroscopic

DOI： 10.1039/C9TC04397G

Kyutacar

Other Link： https://pubs.rsc.org/no/content/articlelanding/2019/tc/c9tc04397g/unauth#!divAbstract

Implication of Molecular Weight on Optical and Charge Transport Anisotropy in PQT-C12 Films Fabricated by Dynamic FTM Reviewed

Atul SM Tripathi, Shifumi Sadakata, Rakesh Kumar Gupta, Shuichi Nagamatsu, Yoshito Ando, Shyam S Pandey

ACS Applied Materials and Interfaces ( The American Chemical Society ) 11 ( 31 ) 28088 - 28095 2019.07

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

Large area (>20 cm × 2 cm)-oriented thin films of PQT-C12 with varying molecular weight and polydispersity index (PDI) were fabricated by the ribbon-shaped floating film transfer method aiming toward their application as an active semiconductor element of organic field effect transistors (OFETs). Investigation on the influence of the molecular weight and PDI upon the extent of molecular alignment and anisotropic charge transport was systematically carried out. It has been demonstrated that high molecular weight in combination with low PDI not only leads to a very high optical anisotropy >10 but also high charge carrier anisotropy with a hole mobility of about 0.07 cm2/V·s for OFETs using parallel-oriented PQT-C12 thin films. Such a structure–property correlation is highly beneficial for the development of high performance organic electronic devices by synergistic and amicable tuning of the optoelectronic anisotropies and polymer synthetic variables.

Kyutacar

Other Link： https://doi.org/10.1021/acsami.9b06568

Wide wavelength photon harvesting in dye-sensitized solar cells utilizing cobalt complex redox electrolyte: Implication of surface passivation Reviewed

Anusha Pradhan, Maryala Saikiran, Gaurav Kapil ,Shuzi Hayase, Shyam S. Pandey

Solar Energy Materials and Solar Cells ( Elsevier ) 195 122 - 133 2019.03

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)

A combination of near infra-red (NIR) photon harvesting and cobalt electrolytes having deeper redox energy level are needed for the fabrication of high efficiency dye-sensitized solar cells (DSSCs). A logical molecular design of unsymmetrical squaraine dye (SQ-110) as a representative of NIR dyes has been demonstrated to function well in DSSC using cobalt complex redox electrolyte. Problem of mass transport limitations due to the bulky cobalt complex ions leading to relatively enhanced charge recombination was amicably solved by single as well as multiple compact metal oxide surface passivation on both of the transparent conducting oxide substrate as well as mesoporous TiO2. Complete absence of light absorption beyond 550 nm wavelength region by D-35 and utilization of a complementary light harvesting dye SQ-110 led to efficient wide wavelength photon harvesting. DSSC fabricated using a dye cocktail of D-35 and SQ-110 in 4:1 ratio resulted in to photoconversion efficiency (PCE) of 7.2%, which is much higher as compared to the constituent individual sensitizers D-35 (3.6%) and SQ-110 (1.9%). This synergistic enhancement in PCE by dye cocktail was associated with the mutual co-operation of respective dyes in terms controlling the dye aggregation and complementary photon harvesting. In this dye cocktail system, D-35 is involved in the prevention of dye aggregation, lower wavelength photon harvesting and energy transfer induced photocurrent enhancement.

DOI： 10.1016/j.solmat.2019.03.013

Kyutacar

Optoelectrical anisotropy in graphene oxide supported polythiophene thin films fabricated by floating film transfer Reviewed

Rajiv K Pandey, Atul SM Tripathi, Shyam S Pandey, Rajiv Prakash

Carbon ( Elsevier ) 147 252 - 261 2019.03

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

A facile method for the fabrication of highly oriented hybrid thin films of conjugated polymer (CP) with graphene oxide (GO) as 2D nano-filler over the high surface tension liquid substrate by floating film transfer is being reported. Formation of the self-assembled oriented hybrid thin film has been validated using multiple characterization techniques. Hybrid thin films thus prepared have been used for the fabrication of organic field effect transistors (OFETs) followed by investigation of anisotropic charge carrier transport. OFETs made with hybrid films oriented in channel direction exhibited the superior device performance with >6 fold augmentation in field effect mobility (μ) and one order improvement in on/off ratio as compared to that of devices based on pristine CP. However, pristine polymer shows 2.2 fold enhancement in mobility and one order augmentation in on/off ratio in parallel orientation as compared to the corresponding perpendicularly oriented films. Thus, our study has elucidated a path to obtain oriented, aligned, and self - assembled hybrid films for further improvement in the device performance aiming towards the applications in organic electronics.

DOI： 10.1016/j.carbon.2019.02.086

Kyutacar

Other Link： https://www.sciencedirect.com/science/article/pii/S0008622319302179

Passivation of Grain Boundary by Squaraine Zwitterions for Defect Passivation and Efficient Perovskite Solar Cells Reviewed

Zhen Wang, Anusha Pradhan, Muhammad Akmal kamarudin, Manish Pandey, Shyam S Pandey, Putao Zhang, Chi huey Ng, Atul SM Tripathi, Tingli Ma, Shuzi Hayase

ACS Applied Materials and Interfaces ( The American Chemical Society ) 11 ( 10 ) 10012 - 10020 2019.02

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

Unavoidable defects in grain boundaries (GBs) are detrimental and critically influence the organometal halide perovskite performance and stability. To address this issue, semiconducting molecules have been employed to passivate traps along perovskite GBs. Here, we designed and synthesized three squaraine molecules (SQ) with zwitterionic structure to interact with under-coordinated Pb2+ and passivate Pb–I antisite defects. Density functional theory calculation shows symmetric O atoms could coordinate with perovskite grains simultaneously, resulting in continuous charge distribution at the SQ–perovskite interface. The energetic traps distribution in CH3NH3PbI3 perovskite is influenced significantly by the interaction between SQ and perovskite as analyzed by thermally stimulated current, in which the deep-level defects are considerably reduced due to efficient SQ passivation. In addition, we explore how SQ …

DOI： 10.1021/acsami.8b22044

Other Link： https://pubs.acs.org/doi/abs/10.1021/acsami.8b22044

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Papers - PANDEY Shyam sudhir