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Influence of the rate of radiation energy on the charge-carrier kinetics application of all-inorganic CsPbBr3 perovskite nanocrystal
Get PDFIn the field of optoelectronics, all-inorganic CsPbBr(3)perovskite nanocrystals (PNCs) have gained significant interest on account of their superb processability and ultra-high stability among all the counterparts. In this study, we conducted an in-depth analysis of CsPbBr3PNCs using joint transient optical spectroscopies (time-resolved photoluminescence and ultrafast transient absorption) in a very comprehensive manner. In order to understand the in-depth analysis of excited-state kinetics, the transient absorption spectroscopy has been performed. The structure of interest of CsPbBr3PNCs was subjected to the rates of the radiation energy of 0.10 mW (kappa(r)/kappa(nr)= similar to 0.62) and 0.30 mW (kappa(r)/kappa(nr)= similar to 0.64). With the rate of radiation energy 0.30 mW, it was observed that there was a significant increase in hot carrier relaxation together with high radiative recombination, resulting in a decrease in charge trappings. Herein, we demonstrate that the tuning of the rate of radiation energies helps to understand the charge-carrier kinetics of CsPbBr3PNCs, which would thus improve the manufacturing of efficient photovoltaic devices
Influence of Vehicular Emissions (NO, NO2, CO and NMHCs) on the Mixing Ratio of Atmospheric Ammonia (NH3) in Delhi, India
Get PDFMixing ratios of atmospheric ammonia (NH3), nitric oxide (NO), carbon monoxide (CO), nonmethane hydrocarbons (NMHCs), and methane (CH4) were measured to investigate the vehicular emissions, which are a dominant source of atmospheric NH3 in urban sites of Delhi, India from January 2013 to December 2014. The annual average mixing ratios of NH3, NO, CO, NMHCs, and CH4 were 21.2 +/- 2.1 ppb, 21.2 +/- 6.1 ppb, 1.89 +/- 0.18 ppm, 0.67 +/- 0.21 ppm and 3.11 +/- 0.53 ppm, respectively. Considering NO as a tracer of vehicular plume, ambient NH3 was correlated with NO during peak traffic hour in the morning (7:00-10:00 h) and evening (17:00-19:00 h) and observed significant positive correlation between them. Result reveals that the mixing ratio of atmospheric NH3 significantly positive correlated with traffic related pollutants (NO, CO, and NHHCs) during all the seasons (winter, summer, and monsoon). During winter, the average mixing ratio of atmospheric NH3 was increased by 1.2-3.5 ppb in the morning peak hour, whereas increased by 0.3-1.6 ppb in the evening peak hour. Similarly, an increase in NH3 mixing ratio was observed during summer (morning: 1.2-2.7 ppb and evening: 1.5-1.6 ppb) and monsoon (morning: 0.4-3.6 ppb and evening: 0.9-1.4 ppb) seasons. The results emphasized that the traffic could be one of the dominant source of ambient NH3 at the urban site of Delhi, as illustrated by positive relationships of NH3 with traffic related co-pollutants (NO, CO and NMHCs)
Low latitude ionospheric response to March 2015 geomagnetic storm using multi-instrument TEC observations over India
Get PDFThe regional ionospheric models are successful in capturing the variability of ionosphere with the inclusion of local ground-based GPS observations and location dependent ionospheric dynamics. In this context, there is a need to develop regional ionospheric maps that aids in improving the consistency of global models. In this paper, an attempt is made to understand the potentiality of multi-instrument observations over Indian region. Four different Total Electron Content (TEC) data sources namely from network of GPS receivers, Ionosonde stations, space based COSMIC radio occultation profiles and SWARM mission data is utilized. The multi-source data is chosen for the geo-magnetic storm conditions prevailed during March 2015. Data from multiple-sources is observed over the period from 15th March 2015 to 20th March 2015. Validation of ground and space-based TEC data with International GNSS service (IGS) station data is significantly observed
Ni-doped Bi0.5Sb1.5Te3 single crystal: a potential functional material for thermoelectricity, topological insulator, and optoelectronics
Get PDFWe report the growth of Ni-doped Bi0.5Sb1.35Ni0.15Te3 single crystal via the self-flux method. The crystalline nature of a grown single crystal was confirmed by the X-ray diffraction technique (XRD). Interestingly, the XRD pattern shows a sharp reflections of type of planes, revealing the growth of the crystal in c-direction. The grown single crystal was subjected for measurement of field dependence magnetization at 300 K and temperature-dependent magnetic moment. The electronic transport property of bulk single crystal was also carried out in a wide range of temperatures from 150 to 450 K. Reasonably large electrical conductivity sigma similar to 1584 S/cm at room temperature was observed which shows similar to 400% enhancement in sigma than the electrical conductivity of bare Bi0.5Sb1.5Te3 single crystal (400 S/cm at 300 K). This enhanced electrical conductivity results to significant power factor similar to 1.68 x 10(- 3)W/m K(2)at 300K which is 163% larger than that of bare Bi0.5Sb1.5Te3 single crystal (6.45 x 10(- 4)W/m K-2). Magnetic properties of a single crystal of Bi0.5Sb1.35Ni0.15Te3 reveal ferromagnetic behavior at 300 K. The photoluminescence (PL) behavior of Bi0.5Sb1.35Ni0.15Te3 single-crystal was also scrutinized. The PL spectra of Bi0.5Sb1.35Ni0.15Te3 single crystal shows the strong red emission peak in the visible region from 600 to 690 nm upon excitation at 375 nm wavelength, which corresponds to the optical bandgap of 2.1 eV
Origin of depressed fill factor in organic solar cells due to S-shape current-voltage characteristics
Get PDFOften, a depressed fill factor is observed in organic solar cells (OSCs), which is usually known as S-shaped current-voltage (J-V) characteristics. To investigate the origin of the depressed fill factor further, a poly[N-9-heptadecanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2,1,3-benzothiadiazole)]:[6,6]-phenyl C71 butyric acid methyl ester based OSC has been characterized through impedance spectroscopy. In addition, the photocurrent vs the applied effective bias plot reveals that the S-shaped J-V characteristics primarily reduce the diffusion current of the device. The present study shows that the diffusion current dominated section of photocurrent reduces with a slope of 2 in the depressed fill factor section given that the slope may further increase as per the impact of the S-shape. The reduction in the diffusion constant (D-n) in the S-shaped region supports the decrease in the diffusion current, which is observed through the photocurrent analysis. It is observed that, in the S-shaped section of the current-voltage characteristics, the transport time for free carriers increases up to 443 mu s. The larger Urbach energy for the active layer of an S-shaped device demonstrates higher subbandgap disorder. Therefore, it is concluded that the accumulation of the charge carriers within the device and disorder in the active layer leads to the S-shaped current-voltage characteristics as well as poor carrier extraction
A comprehensive review on synthesis and applications of single crystal perovskite halides
No full textHalide based perovskite materials have fascinated strong attention for being a hopeful candidate for optoelectronic device applications. Single-crystalline halide perovskites exhibit no grain boundaries and possess low trap densities; and are therefore likely to show superior optoelectronic performances in comparison to their polycrystalline film counterparts. In spite of this, their basic perceptive of physico-chemical properties are however controversial to the scientific society. In this review article, we present the deep insight into all the reported protocols available for the synthesis of purely inorganic as well as hybrid halide perovskites (incorporating organic as well as inorganic cation) to achieve high-quality single crystals. On account of advanced characteristics like long carrier recombination lifetime and exciton diffusion length, wide-ranging visible to NIR absorption, high charge mobility, controllable optoelectronic properties etc., hybrid halide perovskites have emerged to be a tough challenger in the optoelectronic research area in comparison to the purely inorganic halide perovskites and have consequently been paid much attention. Therefore, the optoelectronic properties and convenient applications of particularly hybrid halide single-crystal perovskites in various optoelectronic devices like solar cell, laser, high energy ray detector, photodetector, light-emitting diode, etc are highlighted
Free-standing flexible multiwalled carbon nanotubes paper for wearable thermoelectric power generator
No full textMost of the thermoelectric research, these days, is being focussed towards development of flexible thermoelectric power generators (TEG) for wearable applications. Organic thermoelectric materials being flexible and solution processable, though, seem promising cannot render themselves for designing of conventional thermoelectric devices which require both p- and n-type of legs; due to lack of air-stable and flexible n-type materials. This work shows the possibility of conversion of a p-type flexible free-standing multiwalled carbon nanotubes (MWCNTs) paper into n-type on treatment with polyethylenimine (PEI). X-ray photoelectron spectroscopy results suggest that 'as-grown' MWCNTs attained n-type nature due to electron donation by imine group of PEI. Power factors of similar to 0.2 and similar to 0.06 mu W/mK(2) observed respectively for p- and n-type MWCNTs papers, owing to extremely low thermal conductivity (similar to 0.05W/mK), resulted in figure-of-merit (ZT) of 1.27 x 10(-3) and 3.02 x 10(-4) at 68 degrees C. A prototype TEG designed using 'as-grown' and 'PEI-modified' MWCNTs as p- and n-type thermoelements respectively exhibited output of 227 mu V/7.6 mu A for a temperature difference of 40 degrees C. In short, facile scalability of MWCNTs when collaborated with such a low cost, environment friendly method that can easily modify its conduction to n-type can certainly open opportunities for scalable production of flexible roll-to-roll type wearable thermoelectric modules
Impedimetric humidity sensing studies of Ag doped MCM-41 mesoporous silica coated on silver sputtered interdigitated electrodes
No full textSilver nitrate of desired concentration was doped in the as-synthesized MCM-41 mesoporous silica and the prepared samples are spin coated onto interdigitated thin films with silver on glass slide. The interdigitated thin film electrodes made of silver were fabricated by RF-magnetron sputtering with power of 60 W at 7.2 x 10(-2) mbar. The synthesized samples were characterized for structural and morphological features using FourierTransform Infrared Spectroscopy (FTIR), BET studies and Transmission Electron Microscopy (TEM). Effect of change in the impedimetric analysis for humidity across the interface has been explored. The impedance of Ag-MCM-41 sample changed five orders of magnitude across the humidity range 11%-93% RH. The xAg-MCM-41, where x = 0.07 g has been the better sample for humidity sensing at room temperature. The impedance studies indicate that the sensor system Ag-doped MCM-41 spin coated on silver sputtered interdigitated electrodes is an appropriate candidate to fabricate humidity sensors with enhanced sensing performance
Influence of Electron Transport Layer (TiO2) Thickness and Its Doping Density on the Performance of CH3NH3PbI3-Based Planar Perovskite Solar Cells
Get PDFSimulation studies are vital to understanding solar cell performance and in optimal device design for high-efficiency solar cells. Cell performance is sensitive to many factors, including device architecture, energy band alignment at the interfaces, materials used for photogeneration, charge extraction, doping density and thickness of various layers. The role of electron transport layer (ETL) thickness and its doping density on device performance is explored in this work. As the ETL thickness is increased from 10 nm to 200 nm, both fill factor (FF) and efficiency remain high up to 40 nm, at 0.85 and 28.04%, respectively, and beyond 40 nm, they decrease gradually due to a sharp increase in series resistance, reaching zero at 200 nm. However, J(sc) and V-oc remained unchanged up to an ETL thickness of about 150 nm and 160 nm, respectively. These results were confirmed by contour plots of the simulated V-oc, J(sc), FF and efficiency results. We observed that when ETL approached 200 nm, J(sc) and V-oc decreased to zero and 0.88 V, respectively. This can be attributed to very high series resistance and recombination in the cell. Donor concentration variation in the ETL from 10(17)/cm(3) to 10(20)/cm(3) has much less impact on J(sc), and V-oc remains unchanged. However, fill factor and efficiency improved, which might be due to an increase in conductivity in the ETL. Our result shows that for an optimized device, with an AM 1.5 spectrum, a cell efficiency of 29.64% was achieved with V-oc, J(sc) and fill factor of 1.241 V, 28.70 mA/cm(2) and 0.83, respectively
Modified Calibration Coefficients of Two-Port CPW Standards with Superstrate Effects
No full textCalibration standards are used for the calibration of a vector network analyzer to characterize the microwave components under test. For the direct characterization of coplanar waveguide components, two-port CPW open, short and line are proposed to complement the existing calibration techniques. The developed CPW standards are characterized in the frequency range of 10 MHz to 10 GHz. As these are planar structures, effects of small superstrates on the calibration coefficients of open and short are studied also. The CPW line has shown slight changes in impedance due to superstrates, whereas a few calibration coefficients of open and short standards showed dependence on superstrates. Similar observations are noted by improving the polynomial models of CPW open and short standards up to fifth and sixth order, respectively, which better matches for CPW standards. The reported results are helpful to estimate any change in the measurement uncertainty on using such calibration standards due to superstrates