Thin-film solar cells: an overview Chopra, K. L.; Paulson, P. D.; Dutta, V.
Progress in photovoltaics,
March ‐ May 2004, Letnik:
12, Številka:
2-3
Journal Article
► A time consuming and one step approach of synthesizing hollow microspheres. ► The role of precursor concentration and applied voltage has been investigated. ► Particle size effect on band gap.
...Titanium oxide hollow microspheres were synthesized from organic precursor titanium tetraisopropoxide (TTIP) using continuous spray pyrolysis reactor. Effects of precursor concentration, applied voltage and annealing have been investigated. It was observed that the annealing of the as-synthesized TiO2 hollow microspheres at 250°C, which had an average external diameter of 200nm, leads to an increase in the size and also more spherical shape. The precursor concentration and applied voltage were found to have a direct impact on the size of the microspheres, which is also evident in the absorption spectrum. The as-prepared TiO2 hollow microspheres exhibited good photocatalytic activity for the degradation of MO.
The Covid-19 epidemic caused by Coronavirus emerged as a ‘Pandemic’ for the whole world. This virus denoted as SARS
-
CoV
-
2, causes infections resulting in severe acute respiratory syndrome. The ...viral pandemic completely disrupted the worldwide economy, human health, social behaviours and restricted commercial and industrial activities due to complete and partial lockdowns around the world. In the present study, we analyse the comparative effects of SARS
-
CoV
-
2 (Covid
-
19) on rejuvenation of River Gomti in the 870 km long stretch from Shahjahanpur to Jaunpur in Uttar Pradesh, India. The water quality data have been collected for 3 phases: pre-Covid, lockdown and post-lockdown during January 2019 to April 2021. The data of physicochemical parameters include pH, temperature, electrical conductivity (EC), dissolved oxygen (DO), biological oxygen demand (BOD), Ammoniacal Nitrogen (NH
3
–
N), Boron (B), Calcium (Ca
+2
), Sodium (Na
+1
) and Magnesium (Mg
+2
) ions. The analyses of variance (ANOVA) and mean difference were determined by Tukey’s test (
P
) after discovering normality with Shapiro
-
Wilk’s test. Levene’s test exhibits the group's homogeneity of variance. Pearson's correlation has determined the association among different variables. The results obtained revealed that despite the implementation of the lockdown, the water quality of the river did not witness any notable improvement; instead, it continued to deteriorate. While certain locations experienced a moderate improvement in dissolved oxygen levels during the lockdown, attributed to the closure of industrial effluents, the biochemical oxygen demand remained high. This is largely due to the discharge of untreated or partially treated wastewater into the river. Finally, for future perspective, the paper recommended the need to improve and strengthen the preparation, monitoring, and implementation of policies regarding safe treatment, disposal and management of wastewater during any crisis.
Hydrophobic and surfactant-free ZnO nanoparticles and ZnO decorated graphene nanocomposite (Z@G) with narrow and uniform size distribution were synthesized by a time-efficient microwave-assisted ...hydrothermal reaction that can be used specifically for application in hybrid photovoltaics. The synthesized ZnO nanoparticles and Z@G nanocomposite showed stable and clear dispersion in chloroform and methanol (with volume ratio of 9 : 1) and chloroform and ethanol (volume ratio 9 : 1). Being hydrophobic, these inorganic samples blend very well with organic polymer solution in chlorobenzene, which is a prerequisite to cast smooth and undisrupted film for hybrid solar cell application. The introduction of these hydrophobic nanoparticles into PCPDTBT:PCBM-based bulk-heterojunction polymer solar cells resulted in significant improvement in solar cell J – V characteristics with enhancement in open circuit voltage ( V OC ), short circuit current density ( J SC ) and thereby overall improvement in cell efficiency. With the optimization of the weight ratio of polymer, fullerene and synthesized ZnO nanoparticles/Z@G nanocomposite, the power conversion efficiencies 1.76% and 3.65% were achieved.
An electric field assisted spray deposition method is employed for improving the perovskite film morphology, crystallinity, and surface coverage, and for further fabricating an efficient solar cell. ...By applying different voltages ranging from 0.5 to 2.0 kV during spray deposition, we observed a large variation in the film morphology and surface coverage compared to those fabricated without an electric field, which is due to improved atomization from the Coulomb fission process. The optimized applied voltage of 1.5 kV during spraying led to completion of the reaction between CH3NH3I and PbI2 on a hot substrate for pure phase CH3NH3PbI3 thin film formation with improved grain growth and surface coverage. The cells fabricated using perovskite films showed clear applied voltage dependence in the energy conversion process and alleviation in J-V hysteresis; with 1.5 kV applied voltage the average cell efficiency of 8.9% was obtained compared to films fabricated without applying voltage providing only 6.5%. The best efficiencies are 10.9% and 7.37% for applied voltages of 1.5 kV and 0 kV, respectively. The enhancement in efficiency with applied voltage is due to the formation of more uniform and dense films with large perovskite crystals, which resulted in efficient electron transportation (enhanced photocurrent and modified series and shunt resistances) by minimizing the charge carrier recombination at grain boundaries (resulting in enhanced open circuit voltage). With further optimization of the perovskite film thickness by adjusting the CH3NH3I spray volume, the average cell efficiency of ∼11.0% was obtained.
A polyaniline (Pani) thin film doped with camphorsulfonic acid (CSA) has been deposited using spin coating technique on a glass substrate. Polyaniline is chemically synthesized by an oxidation method ...at ∼0
°C. Sensing experiments are performed on the Pani-CSA thin film with the injection of 50, 100, 150 and 200
ppm level NH
3 at room temperature. The change in resistance, based on the modification of doping level, occurs due to redox interaction of the analyte. Response and recovery times are found to be ∼1
s and ∼7
min, respectively. The hexagonal structure seen in the scanning electron micrograph is helpful in making the sensor response fast.
ZnO nanoparticles were synthesized by the continuous spray pyrolysis technique (CoSP) and the effect of applied voltage across the spray nozzle and an annular ground electrode during spray has been ...studied. X-ray diffraction and transmission electron microscopy studies showed that the product has (hexagonal) wurtzite structure with the average particle size decreasing from 18.5 nm to 12.9 nm in the presence of a high DC voltage (1 kV). The higher value of the absorption peak for the nanoparticles synthesized without voltage is supportive of this behavior. The films deposited by spin coating using these nanoparticles can be used for a variety of applications, particularly as photoelectrodes for dye-sensitized solar cells.
The demand of high-speed wireless communication has increased, which need the data rate to be in the order of Terabyte per second (Tbps) in the near future. Terahertz (THz) band communication is a ...key wireless communication technology to satisfy this future demand. This would also reduce the spectrum scarcity and capacity limitation of current wireless systems. Microfabricated Folded Waveguide TWTs are the potential compact sources of wide band and high-power terahertz radiation. This study primarily focuses on machining technology for THz waveguide components requiring ultra-high precision micromachining. Rectangular waveguides, especially Folded Waveguides (FW), are even more difficult to manufacture using conventional machining techniques due to their small size and very tight tolerances. The criticalities in micromachining of FW for 0.22 THz have been addressed in this article. Half hard free cutting Brass IS 319-H
2
was used as a work material due to its electrical and mechanical properties. Waveguide size of 0.852 × 0.12 mm was machined within ± 3–5 μm linear tolerances, surface roughness in the order of 45 nm
R
a
, and flatness less than half of wavelength (<
λ
/2). The split top and bottom blocks of the folded waveguide were aligned by dowel pins which matched within a tolerance of ± 5 μm. The perpendicularity and parallelism were maintained within 5 μm tolerance. This work explored and established the application of micromilling as reasonably suitable for the THz waveguides followed by ultrasonic cleaning as deburring. It also investigated the measured folded waveguide losses which were close to simulated values.
This work reports ZnO growth by electric field influenced continuous spray pyrolysis reactor over seed layer assisted nanoscale etched Si surface. The comparative studies of ZnO growth in the ...presence and absence electric field on anisotropically etched Si surface are supported by XRD, SEM, EDX, FTIR and reflectance measurements. XRD measurements confirm preferable (002) oriented ZnO growth by certain amount of etching which is reduced with further anisotropic etching. The chlorine incorporation in ZnO thin film measured by EDX and FTIR may be attributed to the seed layer effect. This present investigation show that anisotropic etch pits surface energy profile has played an important role in deciding ZnO nanorods alignment and coalescence amongst ZnO species during self assembly at nucleation sites. It is observed that additional electric field force in spray droplets is enhancing population density, homogeneous growth and surface coverage of Si surface by ZnO nanorods for particular amount of etched Si surface and improved light coupling is confirmed by reflectance measurement. The relevant growth mechanisms for ZnO nanostructure layers comprising nanorods are also discussed.
This work reports deposition of various ZnO nanostructure layers by continuous spray pyrolysis reactor over seed layer assisted nanoscale etched Si surface. The study of various surface morphologies ...of ZnO nanostructure layers are supported by XRD, SEM, photoluminescence and reflectance measurements. The anisotropic etch pits surface energy profile has played an important role in deciding the ultimate surface morphology of ZnO film and may be helpful in generating vertically aligned ZnO nanorods. The 4 min etched Si surface show poor film quality which further improves with Si etching to 8 min. The 8 min etched Si is helping in ZnO growth and with the increase of deposition time shape, size and alignment of ZnO nanorods takes place. XRD pattern show fall of texture coefficient in ZnO growth with deposition time but it remains constant for 8 min etched Si. Photoluminescence study reveals presence of novel defect at 600 nm due to the Si etching and appreciable PL quenching is observed in ZnO growth for 8 min etched Si. Reflectance measurement show light reduction up to 40 and 47 % of existing reflectance in 400–800 nm wavelength regions due to the ZnO growth on 8 min and complete textured Si surface. The growth mechanisms for various ZnO growths are also proposed.
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