Browsing by Author "Neetu"

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A New Series of Heteroleptic Cd(II) Diimine-Ferrocenyl Dithiocarbamate Complexes which Successfully Co-Sensitizes TiO2 Photoanode with Ru N719 Dye in DSSC
(Wiley-Blackwell, 2017) Krishna K. Manar; Neetu; Anamika; Pankaj Srivastava; Michael G. B. Drew; Nanhai Singh
New heteroleptic complexes of the form [Cd(diimine)(Fcdtc)2] (diimine= 1,10-phenanthroline (phen), Fcdtc=N-ferrocenyl-N-pyridin-3-ylmethyl dithiocarbamate (KL1) Cd1; 2,2’-bipyridyl (bpy), N-ferrocenyl-N-pyridin-4-ylmethyl dithiocarbamate (KL2) Cd2; bpy, (KL1) Cd3 and phen, (KL2) Cd4) have been synthesised and characterized by elemental analyses, spectroscopy (IR, UV-Vis., 1H and 13C {1H} NMR) and their structures have been revealed by X-ray crystallography. These complexes have been explored as co-sensitizers with N719 over TiO2 for application as dye sensitized solar cells (DSSC) photoanodes. The use of these complexes as co-sensitizers resulted in extended UV-Visible spectral response, greater dye loading, enhanced electron life time, reduced charge recombination and thermodynamically more facile charge transfer in the DSSC. Among all the co-sensitized cells (Cd1/N719, Cd2/N719, Cd3/N719 and Cd4/N719), the Cd1-based cell demonstrated not only the highest incident photon to current efficiency (IPCE) 47% but the obtained current conversion efficiency 3.84%, was much higher than that of the N719 based cell (2.70%) under the same illumination condition. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Callindra haematocephata and Peltophorum pterocarpum flowers as natural sensitizers for TiO2 thin film based dye-sensitized solar cells
(Elsevier B.V., 2016) Ishwar Chandra Maurya; Neetu; Arun Kumar Gupta; Pankaj Srivastava; Lal Bahadur
We have studied the performance of dye-sensitized solar cells employing natural dye extracted from the flowers Callindra haematocephata and Peltophorum pterocarpum as sensitizers for TiO2 photoanode. The extracts have shown appreciable absorption in the visible region. FTIR studies indicated the presence of anthocyanins and β-carotene in the flowers of C. haematocephata and P. pterocarpum respectively. The extracts were anchored on TiO2 film deposited on transparent conductive glass (FTO) which were used as photoanode. The dye coated TiO2 film electrode, Pt counter electrode and electrolyte (I−3) assembled into a cell module was illuminated by a light source with intensity 100 mW/cm2 to measure the photoelectric conversion efficiency of the DSSCs. From the J-V characteristic curves of cells, the parameters related to the solar cell performance were determined. The conversion efficiency of the DSSC employing natural dye extract from the flower C. haematocephata and P. pterocarpumwere was found as 0.06% and 0.04%, with open-circuit voltage (VOC) of 370 mV & 400 mV, short-circuit current density (JSC) of 0.25 mA/cm2 & 0.15 mA/cm2, fill factor (FF) of 0.70 & 0.71 and Pmax of 65 & 45 μW cm−2 respectively. The extract of the flower C. haematocephata exhibited better photosensitization action compared to the flower of P. pterocarpum. © 2016 Elsevier B.V.
Dye-Sensitized Solar Cells Employing Extracts from Four Cassia Flowers as Natural Sensitizers: Studies on Dye Ingredient Effect on Photovoltaic Performance
(Springer New York LLC, 2018) Ishwar Chandra Maurya; Shalini Singh; Neetu; Arun Kumar Gupta; Pankaj Srivastava; Lal Bahadur
Natural dyes extracted from four different flowers, namely, Cassia surattensis, Cassia tora, Cassia alata and Cassia occidentalis were used as sensitizers for TiO2-based dye-sensitized solar cells (DSSC). The dye extracts from flowers were obtained by a simple extraction technique and used without any further purification. Optical characteristics of dye extracts were studied. Fourier-transform infrared (FTIR) spectra were used to identify the constituents of extracted dyes. The photovoltaic performance of DSSC employing dye-capped TiO2 photoanodes was measured. The sensitization performance related to anchoring groups present and interaction between dyes with TiO2 surface is demonstrated. An attempt has been made to rationalize the observations by light absorption of the dye extracts and their adsorption on TiO2. The short-circuit current density (ISC) values ranged from 0.06 mA/cm2 to 0.20 mA/cm2; open circuit voltage (VOC) from 0.292 V to 0.833 V; fill factor (FF) from 0.7 to 0.9; efficiencies (η) from 0.013% to 0.15% and incident photon-to-current conversion efficiency from 13% to 20%, were obtained for DSSC using these natural dye extracts. Cassia occidentalis showed the highest current density of 0.20 mA/cm2 and power conversion efficiency of 0.15%, which was due to better interaction between the carbonyl and hydroxyl group of the anthocyanin molecule of C. occidentalis and surface of TiO2 film. The red and blue shift of absorption wavelength of C. surattensis and the blue shift of absorption wavelength of the C. tora, C. alata and C. occidentalis extract in ethanol solution compared to that on TiO2 film has been used for the interpretation of obtained results. © 2017, The Minerals, Metals & Materials Society.
Extensive enhancement in power conversion efficiency of dye-sensitized solar cell by using Al-doped TiO2 photoanode
(Springer New York LLC, 2017) Neetu; Ishwar Chandra Maurya; Arun Kumar Gupta; Pankaj Srivastava; Lal Bahadur
In this work, we have prepared Al-doped TiO2 nanoparticles via a hydrothermal method and used it for making photoanode in dye-sensitized solar cell (DSSC). Material characterizations were done using XRD, AFM, SEM, TEM and EDAX. XPS results reveal that Al is introduced successfully into the structure of TiO2 creating new impurity energy levels in the forbidden gap. This resulted in tuning of the conduction band of TiO2 and reduced charge recombination which led to better current conversion efficiency of DSSC. Greater dye loading and enhanced surface area was obtained for Al-doped TiO2 compared to un-doped TiO2. I-V analysis, EIS and Bode plots are employed to evaluate photovoltaic performance. The short-circuit current density (Jsc) and efficiency (η) of cell employing Al-doped TiO2 photoanode were extensively enhanced compared to the cell using un-doped TiO2. The optical band gap (Eg) for Al-doped and un-doped TiO2 was obtained as 2.8 and 3.2 eV, respectively. Jsc and η were 13.39 mAcm−2 and 4.27%, respectively, under illumination of 100 mWcm−2 light intensity when thin films of 1% Al-doped TiO2 was employed as photoanode in DSSC using N719 as the sensitizer dye. With the use of un-doped TiO2 as photoanode under similar conditions, Jsc 5.12 mAcm−2 and η 1.06% only could be obtained. The maximum IPCE% obtained with Al-doped TiO2 and un-doped TiO2 was 67 and 38% respectively at the characteristic wavelength of dye (λmax = 540 nm). The EIS analyses revealed resistive and capacitive elements that provided an insight into various interfacial processes in terms of the charge transport. It was observed that Al-doping reduced the interfacial resistance leading to better charge transport which has improved both photocurrent density and conversion efficiency. Higher electron mobility and fast diffusion resulting in greater charge collection efficiency was obtained for Al-doped TiO2 compared to the un-doped TiO2. Using the Mott–Schottky plot, the donor density was calculated for un-doped and Al-doped TiO2. The work demonstrated that the Al-doped TiO2 is potential photoanode material for low-cost and high-efficiency DSSC. © 2016, Springer-Verlag Berlin Heidelberg.
Homoleptic d10 metal complexes containing ferrocenyl functionalized dithiocarbamates as sensitizers for TiO2 based dye-sensitized solar cells
(Elsevier Ltd, 2018) Neetu; Krishna Kumar Manar; Pankaj Srivastava; Nanhai Singh
Four synthesized d10 metal complexes, namely, ferrocenyl based pyridyl functionalized dithiocarbamates macro-cyclic metal-organic coordination polymers, [M(L)2]∞ (M = Zn(II), L = (N-ferrocenyl-methyl-N-pyridin-4-ylmethyl)dithiocarbamate Zn-2; Cd (II), L = (N-ferrocenyl-methyl-N-pyridin-3-ylmethyl) dithiocarbamate Cd-3 and dimers [M(L)2]2 (M = Zn(II), Hg(II), L = (N-ferrocenyl-methyl-N-pyridin-3-ylmethyl) dithiocarbamate, Zn-1 and Hg-4 were studied for their sensitization activities when anchored on TiO2 thin film electrode and employed as photoanode in dye-sensitized solar cells (DSSC). The absorption spectra of test dyes in dichloromethane solution indicated absorption in 400–500 nm range for all complexes, revealing the possibility of their use as photosensitizers for TiO2. The cyclic voltammetry (CV) demonstrated quasi-reversible behavior for all the complexes. All the dye sensitizers showed significant light harvesting properties with an exceptionally high light-to-electrical energy conversion efficiency (6.23%) shown by Zn-1 complex which was close to that obtained with standard Ru dye, N719 (6.96%) under similar experimental conditions. The better performance of Zn-1 complex compared to other studied dye sensitizers were attributed to its structural features. The extent of interfacial charge recombination and electron lifetime were evaluated by the electrochemical impedance spectroscopy (EIS). © 2018 Elsevier Ltd
Hydrothermal synthesized Nd-doped TiO2 with Anatase and Brookite phases as highly improved photoanode for dye-sensitized solar cell
(Elsevier Ltd, 2020) Neetu; Shalini Singh; Pankaj Srivastava; Lal Bahadur
In this study, the effects of Nd doping on the performance of TiO2 photoanode based dye-sensitized solar cells (DSSC) are reported. Nd-doped TiO2 (Nd-TiO2) was synthesized using hydrothermal method. Un-doped TiO2 (TiO2) was also synthesized for reference. XRD, IR, Raman and electron microscopy characterisation of the obtained material were performed and the subsequent electrochemical tests, CV and EIS studies were made to explore their application. The XRD and Raman analysis's results indicated that the Nd-TiO2 and TiO2 have both the Anatase and Brookite phases. TEM, EDX and EIS studies were used to obtain particle size, morphology, the presence of the element, electron lifetime and recombination characteristics respectively. The Nd-TiO2 nanoparticles have uniform particle size, a strong red shift of their absorption into the visible region and greater dye-loading as compared with TiO2 nanoparticles. It is proved that higher efficiency was achieved when the TiO2 Anatase and Brookite structure were mixed. Further, Nd had a positive effect on the performance of photoelectrode and DSSC fabricated with Nd-TiO2 photoanode revealed an appreciable current conversion efficiency of 5.23% with a short-circuit current (Jsc) of 12.8 mA/cm2, open-circuit voltage (Voc) of 0.62 V and fill factor (FF) of 0.66. The increased current conversion efficiency was attributed to the greater dye loading, reduced charge recombination and facile charge transport with Nd-doped TiO2. © 2020 International Solar Energy Society
N/Al-Incorporated TiO2Nanocompositesfor Improved Device Performance of aDye-Sensitized Solar Cell
(Wiley-Blackwell, 2017) Neetu; Ishwar C. Maurya; Shalini Singh; Arun K. Gupta; Pankaj Srivastava; Lal Bahadur
We report application of aluminium co-doped with nitrogen titania nanocomposite (Al/N-TiO2) prepared by hydrothermal method as photoanode for very efficient dye-sensitized solar cell (DSSC). The Al/N-TiO2 nano-composites are characterized by spectral viz. UV-visible, XRD, FTIR, XPS techniques. TEM, SEM, EDX and BET are used to obtain their particle size, morphology and surface area. The DSSC with Al/N co-doped TiO2 as photoanode and N719 sensitizer dye exhibited an overall light conversion efficiency of 6.24 %, which is much improved compared to that of un-modified TiO2 (1.69 %) under 100 mW/cm2 light irradiation. The improved efficiency with Al/N co-doped TiO2 is attributed to greater dye loading, increased surface area, rapid interfacial charge transfer, slow charge recombination and strong red shift of light absorption in the visible region as compared with un-doped TiO2. The effect of the Al concentration on the current density is studied and optimum Al concentration with N-doped TiO2is observed to be 1.0 mole%. The work establishes that the as prepared Al/N co-doped TiO2is impending photoanode material for low-cost and high-efficiency DSSC. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
NATURAL dye extracted from saraca asoca flowers as sensitizer for TIO2-based dye- sensitized solar cell
(American Society of Mechanical Engineers (ASME), 2016) Ishwar Chandra Maurya; Neetu; Arun Kumar Gupta; Pankaj Srivastava; Lal Bahadur
In this work, we have chosen the low cost natural dye extracted from Saraca asoca flowers to act as a sensitizer dye for TiO2-based dye-sensitized solar cell (DSSC). UV-visible spectroscopic studies of ethanolic extract of dyes have been done in order to understand light absorption behavior of dye. The natural dye extract covers appreciable spectrum of solar radiation, 400-500 nm with an absorption maximum at 450 nm that makes it suitable for use as a photosensitizer in DSSC application. The dye adsorbed onto the semiconductor facilitates electron transfer across the dye/semiconductor interface. FTIR spectra of extract revealed the presence of anchoring groups and coloring constituents. DSSC fabricated with TiO2 and natural dye extract obtained from Saraca asoca flowers as sensitizer has shown open-circuit voltage (Voc) 516 mV, short-circuit current density (Jsc) 0.29 mA/cm2, fill factor (FF) 0.65, incident photon- To-current conversion efficiency (IPCE) 43%, and conversion efficiency of 0.09%. This work briefly discusses the simple extraction technique of natural dye and its performance in DSSC. © VC 2016 by ASME.
Preparation, Characterization and Photosensitizing Activities of Homoleptic Cu(II) Dithiocarbamates in TiO2-Based DSSC
(Wiley-Blackwell, 2019) Krishna K. Manar; Neetu; Kavita Kumari; Anamika; Chote L. Yadav; Pankaj Srivastava; Michael G. B. Drew; Nanhai Singh
New homoleptic copper(II) dithiocarbamate complexes, [Cu(L1-L5)2] (L1=N-benzyl-N-4-bromobenzyl dithiocarbamate− Cu1; L2=N-benzyl-N-4-methoxybenzyl dithiocarbamate− Cu2; L3=4-N,N-diethylbenzyl-N-methyl dithiocarbamate− Cu3; L4=N-methyl-N-4-isopropylbenzyl dithiocarbamate− Cu4 and L5=N-3-pyridyl-N-4-bromobenzyl dithiocarbamate− Cu5) have been synthesized and characterized by elemental analysis, HRMS, IR and UV-Vis. spectroscopy, PXRD and cyclic voltammetry. The monomeric (1−3) and dimeric (4) structures have been elucidated by X-ray crystallography. In all four structures the copper atom has square planar geometry. In 3 and 4 existence of rare C−H⋅⋅⋅Cu intermolecular anagostic interactions have been detected in the solid state. All complexes were exploited as sensitizers for TiO2 photoanode based dye-sensitized solar cells (DSSC). When TiO2 anchored with these complexes was used as DSSC photoanode, significant light harvesting properties were observed with an exceptionally high light-to-electrical energy conversion efficiency (3.62%) shown by Cu3 complex. The extent of interfacial charge-recombination and electron lifetime was evaluated from the electrochemical impedance spectroscopy (EIS) studies. The better performance of Cu3 compared to other complexes was attributed to its structural features. All the complexes with σrt, 10−6-10−9 S cm−1 are weakly conducting but show semiconducting behaviour in the 303–383 K temperature range with Ea values of 0.20−0.90 eV. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim