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R. Dhar - One of the best experts on this subject based on the ideXlab platform.
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dielectric characteristics of highly ionic antiferroelectric liquid Crystalline Material
Journal of Molecular Liquids, 2018Co-Authors: Avneesh Mishra, R Dabrowski, R. DharAbstract:Abstract We report dielectric spectroscopy of a room temperature single phase antiferroelectric liquid Crystalline Material namely (S) + (1-methylheptyloxycarbonyl)2-fluorophenyl 4′-(3-perfluoropropylmethylnoyloxy prop-1-oxy)biphenyl-4-carboxylate in the frequency range 1 Hz to 35 MHz under planar anchoring conditions of the molecules. Dielectric, thermodynamic and texture studies confirm a wide room temperature range single antiferroelectric (SmC⁎a) phase between crystal and isotropic phase of this Material. Three relaxation modes (due to collective as well as individual molecular process) appeared in the SmC⁎a phase. The contribution of ionic conductivity in SmC⁎a phase has also been determined.
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gold nanoparticles in plastic columnar discotic liquid Crystalline Material
Thermochimica Acta, 2016Co-Authors: Mukesh Mishra, Sandeep Kumar, R. DharAbstract:Abstract We have studied the effect of gold nanoparticles (GNPs) on the thermodynamical, optical and dielectrical parameters of a discotic liquid crystal (DLC) namely hexabutyloxytriphenylene (HAT4). It has been observed that with the increase of GNPs concentration in DLC, composites shows two different regions. In the first regions i.e. low concentrations ( hp -I L ) transition temperature and enthalpy (ΔH) decrease rapidly while in the second region i.e. higher concentrations (>1 wt%) Col hp -I L transition temperature and ΔH are approximately constant. It has been observed that, in the case of composites having 0.2 and 0.6 wt% of GNPs, conductivity has enhanced but it is poor as compared to the composite having 1.2 wt% of GNPs. For 1.2 wt% of GNPs, conductivity has increased by seven orders of magnitude as compared to the DLC. Optical study suggests that band gap of nanocomposites has decreased due to dispersion of GNPs.
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bulk heterojunction solar cells based on self assembling disc shaped liquid Crystalline Material
Liquid Crystals, 2015Co-Authors: Manisha Bajpai, Neelam Yadav, Sandeep Kumar, Ritu Srivastava, R. DharAbstract:ABSTRACTIn this article, effect of addition of disc-shaped liquid Crystalline Material, namely 2, 3, 6, 7, 10, 11-hexabutyloxytriphenylene, in poly (3-hexylthiophene): [6, 6]-phenyl-C61-butyric acid methyl ester containing bulk heterojunction (BHJ) solar cells has been investigated. These disc-shaped molecules organise into ordered columnar hexagonal structures through intermolecular π − π interactions as monitored by polarised light optical microscopy. Current–voltage characteristics of the device prepared with liquid crystal layer exhibited a short-circuit current of 10.5 mA cm−2 and a fill factor of 35%. The resultant power conversion efficiency (PCE) was 1.54%. The influence of varying the thickness of liquid crystal layer and annealing on these solar cells was also studied. The short circuit current and PCE of 12.9 mA cm−2 and 2.3% was achieved for these BHJ solar cells containing self-organised discotic liquid crystals in the active layer under one sun condition after annealing.
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thermodynamical electrical and electro optical studies of a room temperature tri component antiferroelectric liquid Crystalline Material
Phase Transitions, 2014Co-Authors: Avneesh Mishra, Magdalena Zurowska, R Dabrowski, R. DharAbstract:Thermodynamic and electric studies show the wide room temperature range antiferroelectric SmC*a (91.1 to −20.0 oC) phase in addition to narrow temperature range paraelectric SmA* (∼2.1 oC) and ferroelectric SmC* (∼4.3 oC) phases in thestudied antiferroelectric Material. Frequency-dependent dielectric studies show five different relaxation modes appearing in SmA*, SmC* and SmC*a phases under the planar anchoring condition of the molecules. The ferroelectric SmC* to paraelectric SmA* transition temperature has been found to be 97.3 oC using Curie–Weiss law. The dielectric response of SmC*a phase exhibits three relaxation modes in addition to Goldstone mode in SmC* phase and soft mode in SmA* phase. Polarizations, switching time and rotational viscosity have also been determined. Maximum value of polarization (P) is ∼300 nC/cm2. Switching time is the order of few milliseconds.
Wojciech Pisula - One of the best experts on this subject based on the ideXlab platform.
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a molecular nematic liquid Crystalline Material for high performance organic photovoltaics
Nature Communications, 2015Co-Authors: Kuan Sun, Zeyun Xiao, Wojciech Zajaczkowski, Rachel M. Williamson, Eric Hanssen, Wojciech Pisula, Jonathan M White, Jianyong Ouyang, Jegadesan Subbiah, Andrew B HolmesAbstract:There is a trade-off between increasing thickness of active layers in organic photovoltaic cells to be compatible with modern printing techniques and decreasing it to improve the device performance. Sun et al. report a nematic liquid Crystalline molecular electron donor Material used in thick layers.
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A molecular nematic liquid Crystalline Material for high-performance organic photovoltaics
Nature Communications, 2015Co-Authors: Kuan Sun, Zeyun Xiao, Wojciech Zajaczkowski, Rachel M. Williamson, Shirong Lu, Eric Hanssen, Jeyamkondan Subbiah, Wojciech Pisula, Jonathan M White, Jianyong OuyangAbstract:Solution-processed organic photovoltaic cells (OPVs) hold great promise to enable roll-to-roll printing of environmentally friendly, mechanically flexible and cost-effective photovoltaic devices. Nevertheless, many high-performing systems show best power conversion efficiencies (PCEs) with a thin active layer (thickness is ~100 nm) that is difficult to translate to roll-to-roll processing with high reproducibility. Here we report a new molecular donor, benzodithiophene terthiophene rhodanine (BTR), which exhibits good processability, nematic liquid Crystalline behaviour and excellent optoelectronic properties. A maximum PCE of 9.3% is achieved under AM 1.5G solar irradiation, with fill factor reaching 77%, rarely achieved in solution-processed OPVs. Particularly promising is the fact that BTR-based devices with active layer thicknesses up to 400 nm can still afford high fill factor of ~70% and high PCE of ~8%. Together, the results suggest, with better device architectures for longer device lifetime, BTR is an ideal candidate for mass production of OPVs.
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uniaxial alignment of the columnar super structure of a hexa alkyl hexa peri hexabenzocoronene on untreated glass by simple solution processing
Journal of the American Chemical Society, 2003Co-Authors: A Tracz, Wojciech Pisula, Jeremiasz K Jeszka, Mark D Watson, Klaus Mullen, Tadeusz PakulaAbstract:Uniaxially aligned, thin films of a discotic columnar thermotropic liquid Crystalline Material can be prepared by a simple solution zone-casting method, without the need for modified surfaces or traditional alignment techniques. Atomic force microscopy together with X-ray diffraction reveals single-Crystalline-like order over several square centimeters, far exceeding the requirements for application of such films in organic molecular electronic devices such as field-effect transistors.
Jianyong Ouyang - One of the best experts on this subject based on the ideXlab platform.
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a molecular nematic liquid Crystalline Material for high performance organic photovoltaics
Nature Communications, 2015Co-Authors: Kuan Sun, Zeyun Xiao, Wojciech Zajaczkowski, Rachel M. Williamson, Eric Hanssen, Wojciech Pisula, Jonathan M White, Jianyong Ouyang, Jegadesan Subbiah, Andrew B HolmesAbstract:There is a trade-off between increasing thickness of active layers in organic photovoltaic cells to be compatible with modern printing techniques and decreasing it to improve the device performance. Sun et al. report a nematic liquid Crystalline molecular electron donor Material used in thick layers.
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A molecular nematic liquid Crystalline Material for high-performance organic photovoltaics
Nature Communications, 2015Co-Authors: Kuan Sun, Zeyun Xiao, Wojciech Zajaczkowski, Rachel M. Williamson, Shirong Lu, Eric Hanssen, Jeyamkondan Subbiah, Wojciech Pisula, Jonathan M White, Jianyong OuyangAbstract:Solution-processed organic photovoltaic cells (OPVs) hold great promise to enable roll-to-roll printing of environmentally friendly, mechanically flexible and cost-effective photovoltaic devices. Nevertheless, many high-performing systems show best power conversion efficiencies (PCEs) with a thin active layer (thickness is ~100 nm) that is difficult to translate to roll-to-roll processing with high reproducibility. Here we report a new molecular donor, benzodithiophene terthiophene rhodanine (BTR), which exhibits good processability, nematic liquid Crystalline behaviour and excellent optoelectronic properties. A maximum PCE of 9.3% is achieved under AM 1.5G solar irradiation, with fill factor reaching 77%, rarely achieved in solution-processed OPVs. Particularly promising is the fact that BTR-based devices with active layer thicknesses up to 400 nm can still afford high fill factor of ~70% and high PCE of ~8%. Together, the results suggest, with better device architectures for longer device lifetime, BTR is an ideal candidate for mass production of OPVs.
Kuan Sun - One of the best experts on this subject based on the ideXlab platform.
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a molecular nematic liquid Crystalline Material for high performance organic photovoltaics
Nature Communications, 2015Co-Authors: Kuan Sun, Zeyun Xiao, Wojciech Zajaczkowski, Rachel M. Williamson, Eric Hanssen, Wojciech Pisula, Jonathan M White, Jianyong Ouyang, Jegadesan Subbiah, Andrew B HolmesAbstract:There is a trade-off between increasing thickness of active layers in organic photovoltaic cells to be compatible with modern printing techniques and decreasing it to improve the device performance. Sun et al. report a nematic liquid Crystalline molecular electron donor Material used in thick layers.
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A molecular nematic liquid Crystalline Material for high-performance organic photovoltaics
Nature Communications, 2015Co-Authors: Kuan Sun, Zeyun Xiao, Wojciech Zajaczkowski, Rachel M. Williamson, Shirong Lu, Eric Hanssen, Jeyamkondan Subbiah, Wojciech Pisula, Jonathan M White, Jianyong OuyangAbstract:Solution-processed organic photovoltaic cells (OPVs) hold great promise to enable roll-to-roll printing of environmentally friendly, mechanically flexible and cost-effective photovoltaic devices. Nevertheless, many high-performing systems show best power conversion efficiencies (PCEs) with a thin active layer (thickness is ~100 nm) that is difficult to translate to roll-to-roll processing with high reproducibility. Here we report a new molecular donor, benzodithiophene terthiophene rhodanine (BTR), which exhibits good processability, nematic liquid Crystalline behaviour and excellent optoelectronic properties. A maximum PCE of 9.3% is achieved under AM 1.5G solar irradiation, with fill factor reaching 77%, rarely achieved in solution-processed OPVs. Particularly promising is the fact that BTR-based devices with active layer thicknesses up to 400 nm can still afford high fill factor of ~70% and high PCE of ~8%. Together, the results suggest, with better device architectures for longer device lifetime, BTR is an ideal candidate for mass production of OPVs.
Tripti Vimal - One of the best experts on this subject based on the ideXlab platform.
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effect of metallic silver nanoparticles on the alignment and relaxation behaviour of liquid Crystalline Material in smectic c phase
Journal of Applied Physics, 2017Co-Authors: Tripti Vimal, Swadesh Kuma Gupta, Rohi Katiya, Atul Srivastava, Michal Czerwinski, Katarzyna Krup, Sandeep Kuma, Rajiv ManohaAbstract:The influence of silver nanoparticles dispersed in a Ferroelectric Liquid Crystal (FLC) on the properties of the resultant composite system has been investigated by thermal, electro–optical, and dielectric methods. We show that the concentration of thiol capped silver nanoparticles is a critical factor in governing the alignment of nanoparticles (NPs) in the host FLC. The orientation of NPs in composite samples affects the ordering of the LC (Liquid Crystal) phase and consequently changes the various phase transition temperatures of the host LC. Formation of self-assembled 2D (two dimensional) arrays of nanoparticles is observed for high concentration of dopant in the LC, oriented perpendicular to the direction of rubbing. We propose that the molecular interaction between the thiol capped NPs and LC molecules is the key factor behind such an arrangement of NPs. Orientation of NPs has affected the relaxation behaviour and various other Material parameters, significantly. A noteworthy change in DC conductivity articulates our proposed idea of the formation of 2D array of NPs perpendicular to the direction of rubbing. This comprehensive study endorses the importance of dopant concentration in modifying the properties of the host LC Material.The influence of silver nanoparticles dispersed in a Ferroelectric Liquid Crystal (FLC) on the properties of the resultant composite system has been investigated by thermal, electro–optical, and dielectric methods. We show that the concentration of thiol capped silver nanoparticles is a critical factor in governing the alignment of nanoparticles (NPs) in the host FLC. The orientation of NPs in composite samples affects the ordering of the LC (Liquid Crystal) phase and consequently changes the various phase transition temperatures of the host LC. Formation of self-assembled 2D (two dimensional) arrays of nanoparticles is observed for high concentration of dopant in the LC, oriented perpendicular to the direction of rubbing. We propose that the molecular interaction between the thiol capped NPs and LC molecules is the key factor behind such an arrangement of NPs. Orientation of NPs has affected the relaxation behaviour and various other Material parameters, significantly. A noteworthy change in DC conductiv...
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thermal and optical study of semiconducting cnts doped nematic liquid Crystalline Material
Phase Transitions, 2016Co-Authors: Tripti Vimal, Shivani Pandey, Swadesh Kumar Gupta, Dharmendra Pratap Singh, Kaushlendra Agrahari, Rajiv ManoharAbstract:We report the thermal and spectroscopic analysis of the carbon nanotubes (CNTs)-doped nematic liquid crystal (NLC) Material. The CNTs have been oriented in the p-ethoxybenzylidene p-butylaniline NLC. The thermal study of the CNTs doped nematic mixtures shows a significant decrease in the isotropic to nematic phase transition temperature. However higher doping concentration of CNTs has led to the further increase in transition temperature. The UV-Visible spectroscopy has been attempted on the CNTs/NLC mixtures at room temperature. The investigated NLC present one absorption band corresponding to π–π* electronic transition. A red shift of λmax with the increasing concentration of CNTs in the mixture has been observed. The band gap of NLC has been found to decrease after the doping of CNTs. The absorbance was measured for the UV light, polarized parallel and perpendicular to the LC director in the planar aligned cell.
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enhanced negative dielectric anisotropy and high electrical conductivity of the swcnt doped nematic liquid Crystalline Material
Journal of Molecular Liquids, 2015Co-Authors: Tripti Vimal, Shivani Pandey, Swadesh Kumar Gupta, Dharmendra Pratap Singh, Rajiv ManoharAbstract:Abstract We report a significant improvement in the dielectric anisotropy of single wall carbon nanotube (SWCNT) doped p-ethoxybenzylidene p-butylaniline (EBBA) nematic liquid crystal (NLC). The modification in physical parameters of the doped system shows strong dependence on the concentration of SWCNTs. The presence of SWCNTs changes the physical properties like splay elastic constant, rotational viscosity and electrical conductivity of the pristine nematic LC remarkably. The behavior of electrical conductivity was found to be considerably dependent on the orientation of CNTs in nematic matrix influenced by applied probing field. Enhanced dielectric anisotropy and conductivity of the doped system show its utility in the improvement of variety of liquid crystal devices.