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Dual-functional cathode buffer layer for power conversion efficiency enhancement of bulk-heterojunction solar cells
No full textHere, we report a luminescent cathode buffer layer (CBL) for power conversion efficiency (PCE) enhancement of organic solar cells (OSCs). ZnO doped with Aluminum (Al) and Europium (Eu) was cast as CBL by a solution-processed method. CBL serves a dual purpose by acting both as a spectral conversion and an electron transporting layer. The luminescent ZnO:Al,Eu CBL layer has broad absorption spanning the ultraviolet (300-400 nm) spectrum, contributing to absorption enhancement. Moreover, the emission of CBL layer overlaps with the absorption of poly [N -9'-heptadecanyl-2,7-carbazole- alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) polymer thus elevating the overall absorption of the active layer and improving the photocurrent With this ZnO:Al,Eu CBL in the inverted device configuration (ITO/CBL/active layer/MoOx/Al), an enhanced power conversion efficiency (PCE) of 6.9% was obtained while the device with pristine ZnO as CBL showed PCE of 5.9%. A blend of PCDTBT donor and [6,6]-phenyl C-71 butyric acid methyl ester (PC71BM) acceptor was used as an active layer in both the cases. In ZnO:Al,Eu CBL layer, Al doping improves the conductivity, while Eu doping significantly enhances the emission in the visible region by down-shifting the incoming solar UV light to the visible range which overlaps with the absorption of PCDTBT polymer resulting in energy transfer and improved overall device efficiency. The findings of the study show the significance of luminescent znO:ALEu nanoparticle CBL in enhancing the performance of organic solar cells
Enhanced photoelectrochemical performance of TiO2 photoanode decorated with Pd-carbon core shell nanoparticles
No full textIn this work, we report enhancement in photoelectrochemical performance of TiO2 photo-anode on coating it with Palladium carbon (Pd-C) core shell nanoparticles. Transmission electron microscopy images confirmed formation of Pd nanoparticle and Pd-C nanoparticles with Pd core surrounded by carbon shell. X-Ray Diffraction analysis confirmed the pure anatase phase of synthesized TiO2 films. Raman spectroscopy revealed graphitic nature of carbon in Pd-C. In comparison to pristine TiO2, quenching in PL intensity of Pd-TiO2& Pd-C-TiO2 sample was observed which indicates lowering of recombination rate of charge carriers, this effect is explained through surface plasmon resonance (SPR) in Pd and Pd-C nanoparticles. Also, SPR in Pd & Pd-C promoted absorption of photons in visible region thus making both Pd-C-TiO2& Pd-TiO2 active in visible region. Finally, graphitic carbon layer over Pd in Pd-C-TiO2 offered an additional advantage over bare Pd in Pd-TiO2 i.e. reducing the charge transfer resistance between electrode and electrolyte under illumination
Analysing the TIPSP-based VOFET through transistor efficiency (g(m)/I-D)
No full textA simple vertical organic field-effect transistor (VOFET) structure has been fabricated using ambipolar 6, 13-bis (triisopropylsilyl ethynyl) pentacene (TIPSP) with a channel length (L) of 90 nm. This device can operate at -2 V which is much lower than the voltage, reported so far for the organic devices based on TIPSP. The first time, the authors are using transistor efficiency to extract VOFET's parameters. The threshold voltage (V-th) of the device has been found to vary between 0.18 and 0.38 V with the current on/off ratio (I-on/I-off) of 10(4). The mobility (mu) of the device has been calculated as 0.62 cm(2)/Vs. The sub-threshold slope, transconductance (g(m)), output conductance (g(d)), and early voltage (V-E) have been found to be 140 +/- 30 mV/decade, 2 mu S, 10(-6) S, and 1.3 +/- 2 V, respectively
Copper Bromide as an Efficient Solution-Processable Hole Transport Layer for Organic Solar Cells: Effect of Solvents
Get PDFIn this work, we report copper bromide (CuBr) as an efficient, inexpensive, and solution-processable hole transport layer (HTL) for organic solar cells (OSCs) for the first time. To examine the effectiveness of the material in general, three different solvents such as acetonitrile (MeCN), dimethyl sulfoxide (DMSO), and dimethylformamide (DMF) are used for solution-processing thin-film deposition of CuBr. CuBr thin films deposited from different solvents show high transparency and no significant difference has been observed in absorption in the visible and near-IR range, whereas a slight difference has been found in the near-UV range by changing the solvents. Furthermore, two most studied combinations of the active layer such as PTB7/PC71BM and PCDTBT:/PC71BM are used for device fabrication with geometry of ITO/CuBr(HTL) active layer/Al. By using CuBr as a HTL in OSCs, the power conversion efficiencies (PCEs) have been achieved to up to 5.16 and 4.72% with PTB7/PC71BM and PCDTBT/PC71BM active layers, respectively. The CuBr film from DMF solvent shows highest PCE as compared to films deposited from DMSO and MeCN solvents. Different solvents used for HTL deposition have a major effect on the fill factor (FF), while very little difference on open circuit voltage (V-oc) and short circuit current (J(sc)) has been observed. It may be mentioned here that a small difference of device parameters (PCE, FF, J(sc), and V-oc) has been observed in the devices using the HTL deposited from DMF and DMSO solvents, whereas a significant difference of the device parameters has been found in devices using the HTL from MeCN solvent
Development of hydraulic cross floating valve
No full textThis paper describes the design, simulation, development, and analysis of a Cross Floating Valve (CFV), an important instrument used in a cross float or pressure calibration system of pressure balances (PBs) to make the calibration process easy and time efficient. The design aspects of the CFV include the selection of proper materials and modeling of various necessary components of the CFV. For the piston design, 5 different materials, SS304, SS316, Aermet 340, SS440C, and AISI17-4PH were used. After the design, simulation studies were carried out using the ANSYS (Workbench R15.0) software to understand the behavior of stress, strain, and deformation. Out of the 5 materials thus used, the values of the factor of safety of 2 materials (SS304 and SS316) were found to be below expectations and hence were not used in the fabrication process. Among the rest of the 3 other materials (AISI17-4PH, SS440C, and Aermet 340) having a factor of safety within the expected limits, Aermet 340 was also ignored because of its high cost. Finally, AISI17-4PH and SS440C were used to fabricate the piston, the most important and critical component of the CFV. The final CFV thus developed was tested for its performance in the cross floating experiments with 2 different sets of PBs. The results thus obtained show that the use of CFV reduces the calibration time considerably which is approximately 30% (average time of increasing and decreasing orders of pressure) from the time taken in performing calibration without using CFV, which is a significant achievement
Source Apportionment of PM10 Over Three Tropical Urban Atmospheres at Indo-Gangetic Plain of India: An Approach Using Different Receptor Models
Get PDFThe present work is the ensuing part of the study on spatial and temporal variations in chemical characteristics of PM10 (particulate matter with aerodynamic diameter <= 10 mu m) over Indo Gangetic Plain (IGP) of India. It focuses on the apportionment of PM10 sources with the application of different receptor models, i.e., principal component analysis with absolute principal component scores (PCA-APCS), UNMIX, and positive matrix factorization (PMF) on the same chemical species of PM10. The main objective of this study is to perform the comparative analysis of the models, obtained mutually validated outputs and more robust results. The average PM10 concentration during January 2011 to December 2011 at Delhi, Varanasi, and Kolkata were 202.3 +/- 74.3, 206.2 +/- 77.4, and 171.5 +/- 38.5 mu g m(-3), respectively. The results provided by the three models revealed quite similar source profile for all the sampling regions, with some disaccords in number of sources as well as their percent contributions. The PMF analysis resolved seven individual sources in Delhi [soil dust (SD), vehicular emissions (VE), secondary aerosols (SA), biomass burning (BB), sodium and magnesium salt (SMS), fossil fuel combustion, and industrial emissions (IE)], Varanasi [SD, VE, SA, BB, SMS, coal combustion, and IE], and Kolkata [secondary sulfate (Ssulf), secondary nitrate, SD, VE, BB, SMS, IE]. However, PCA-APCS and UNMIX models identified less number of sources (besides mixed type sources) than PMF for all the sampling sites. All models identified that VE, SA, BB, and SD were the dominant contributors of PM10 mass concentration over the IGP region of India
Zinc Phthalocyanine Nanowires based Flexible Sensor For Room Temperature Cl-2 Detection
No full textWe have fabricated highly sensitive and Cl-2 selective flexible sensor by depositing solution processed zinc phthalocyanine nanowires onto the flexible PET substrate and studied its Cl-2 sensing characteristics in Cl-2 concentration range 5-1500 ppb. The flexible sensor has a minimum detection limit as low as 5 ppb of Cl, and response as high as 550% within 10 seconds. Interestingly, the sensor exhibited enhanced and faster response kinetics under bending conditions. The gas sensing mechanism of sensor has been discussed on the basis of XPS and Raman spectroscopic studies which revealed that zinc ions were the preferred sites for Cl-2 interactions
Spectroscopic study of Pr3+ ions doped Zinc Lead Tungsten Tellurite glasses for visible photonic device applications
No full textZinc Lead Tungsten Tellurite (ZnPbWTe) glasses doped with different Pr3+ ion concentrations having the composition 5ZnO + 15PbO + 20WO(3) (60-x)TeO2 + xPr(6)O(11) (where x = 0.5, 1, 1.5, 2.0 and 2.5 mol%) were prepared by using sudden quenching technique and characterized to understand their visible emission characteristic features using spectroscopic techniques such as absorption, excitation and emission. The Judd-ofelt (J-O) theory has been applied to the absorption spectral features with an aim to evaluate various radiative properties for the prominent fluorescent levels of Pr(3+)ions in the as-prepared glasses. The emission spectra recorded for the as-prepared glasses under 468 nm excitation show three prominent emission transitions P-3(0) -> H-3(6), P-3(0) -> F-3(2) and P-3(1) -> F-3(4), of which P-3(0) -> F-3(2) observed in visible red region (648 nm), is relatively more intense. The intensity of P-3(0) -> F-3(2) emission transition in the titled glasses increases up to 1mol% of Pr3+ ions and beyond concentration quenching is observed. Branching ratios (beta(R)) and emission cross-sections (sigma(se)) were estimated for P-3(0) -> F-3(2) transition to understand the luminescence efficiency in visible red region (648 nm). The CIE chromaticity coordinates were also evaluated in order to understand the suitability of these glasses for visible red luminescence devices. From the emission cross-sections, quantum efficiency and CIE coordinates, it was concluded that 1 mol% of Pr3+ ions in ZnPbWTe glasses are quite suitable for preparing visible reddish orange luminescent devices
Study on nanocrystalline silicon thin films grown by the filtered cathodic vacuum arc technique using boron doped solid silicon for fast photo detectors
No full textThis paper reports the synthesis and properties of as grown and hydrogenated nanocrystalline silicon (nc-Si or nc-Si:H) thin films deposited by the filtered cathodic vacuum arc technique using boron doped solid silicon as a cathode. No hazardous gases like silane, diborane etc. (which are used in the conventional growth techniques) were used for the growth of nc-Si or nc-Si:H films in this process. These films have been characterized by X-ray diffraction (XRD), scanning electron microscopy, UV-visible spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and photo detection measurements. The XRD patterns show the amorphous and nanocrystalline coexisting nature of the films deposited under different deposition conditions. Raman spectra also reveal the amorphous nature of the film deposited at room temperature, whereas the films deposited at high temperature and under hydrogen environment silicon films showed the nanocrystalline nature. The evaluated values of dark conductivity (sigma(D)), activation energy (Delta(g)), optical band gap (E-g) vary from 3.6 x 10(-5) to 7.2 x 10(-3) ohm(-1) cm(-1), from 0.55 to 0.24 eV and from 1.24 to 2.12 eV, respectively, in nc-Si or nc-Si:H films. The fast response and recovery time as 4.92 and 4.06 s have been observed for the photo detectors developed from the nc-Si:H films deposited at room temperature
Necessity of 'two time zones: 1ST-I (UTC+5: 30 h) and 1ST-II (UTC+6: 30 h)' in India and its implementation
Get PDFA strong demand of a separate time zone by northeast populace has been a matter of great debate for a very long period. However, no implementable solution to this genuine problem has yet been proposed. The CSIR-National Physical Laboratory, CSIR-NPL (the National Measurement Institute, NMI, of India and custodian of Indian Standard Time, 1ST) proposes an implementable solution that puts the country in two time zones: (1) IST-I (UTC + 5 : 30 h, represented by longitude passing through 82 degrees 33E) covering the regions falling between longitude 68 degrees 7 E and 89 degrees 52 E and (ii) IST-II (UTC + 6 : 30 h, represented by longitude passing through 97 degrees 30 E) encompassing the regions between 89 degrees 52 E and 97 degrees 25 E. The proposed demarcation line between IST-I and IST-II, falling at longitude 89 degrees 52 E, is derived from analyses of synchronizing the circadian clocks to normal office hours (9 : 00 a.m. to 5 : 30 p.m.). This demarcation line passes through the border of West Bengal and Assam and has a narrow spatial extension, which makes it easier to implement from the railways point of view. Once approved, the implementation would require establishment of a laboratory for 'Primary Time Ensemble - II' generating IST-II in any of the north-eastern states, which would be equivalent to the existing 'Primary Time Ensemble-I' at CSIR-NPL, New Delhi