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Item New indole based co-sensitizers for dye sensitized solar cells exceeding 10% efficiency(Royal Society of Chemistry, 2016) Babu, D.D.; Su, R.; El-Shafei, A.; Vasudeva Adhikari, A.V.In this work, we report the molecular engineering and synthesis of three novel indole co-sensitizers DBA-3, DBA-4 and DBA-5 with D–D–A (donor–donor–acceptor) architecture. In the quest to comprehend the role of auxiliary donors on co-sensitization, we have incorporated auxiliary electron donating moieties with varying geometries and electron donating capabilities to the indole moiety in order to obtain the aforementioned co-sensitizers. Their electrochemical and photo-physical properties along with molecular geometries, obtained from Density Functional Theory (DFT) are studied to vindicate the effect of the co-sensitizer structures on the photovoltaic properties of DSSCs. Furthermore, for the first time we demonstrate the profound effect of auxiliary donor groups on the co-sensitization performance of the organic molecules. Devices co-sensitized using DBA-3, DBA-4 and DBA-5 along with ruthenium sensitizer NCSU-10, displayed significantly different photovoltaic conversion efficiencies (PCEs) when compared to that of the device sensitized using only NCSU-10. The photovoltaic and EIS studies revealed that, the co-sensitizer DBA-4 succeeded in enhancing the light harvesting capability as well as efficiently suppressing undesirable charge recombinations in the cell. Due to the aforementioned reasons, a cell co-sensitized using DBA-4 has shown promising photovoltaic results and exhibited an enhanced overall efficiency of 10.12%. Furthermore, vertical electronic excitations, calculated using TD-DFT, are in good agreement with the experimental l max results, which clearly indicates that, the energy functional and basis set utilized in this study can be effectively employed for predicting the absorption spectra of novel photosensitizers, with high confidence prior to their synthesis. All these results provide a better understanding and deeper insight into the intricacies involved in the design of superior co-sensitizers to further improve the performance of DSSCs. This journal is © The Royal Society of Chemistry 2016Item From Molecular Design to Co-sensitization; High performance indole based photosensitizers for dye-sensitized solar cells(Elsevier Ltd, 2016) Babu, D.D.; Su, R.; El-Shafei, A.; Vasudeva Adhikari, A.V.Herein, we report the molecular design and synthesis of two novel organic co-adsorbers DBA-1((Z)-2-cyano-3-(5-(4-(cyclohexa-1,5-dien-3-ynyl(phenyl)amino)phenyl)-1-hexyl-1H-indol-3-yl)acrylic acid) and (DBA-2) 5-((5-(4-(diphenylamino)phenyl)-1-hexyl-1H-indol-3-yl)methylene)pyrimidine-2,4,6(1H,3H,5H)-trione with D-D-A (donor-donor-acceptor) architecture. We have combined the strong electron donating triphenylamine group with indole moiety attached to different acceptors/anchoring groups, as co-adsorbers for dye-sensitized solar cells and we present for the first time, the role of anchoring/acceptor unit on their co-adsorption properties. In this study, cyanoacetic acid and barbituric acid are employed as anchoring groups in the co-sensitizers DBA-1 and DBA-2, respectively. Their electrochemical and photo-physical properties along with molecular geometries, obtained from Density Functional Theory (DFT) are employed to vindicate the effect of co-sensitizer structures on photovoltaic properties of DSSCs. We have demonstrated that the co-sensitization effect is profoundly dependent upon the anchoring/acceptor unit in the co-adsorber molecule. Devices co-sensitized using DBA-1 and DBA-2 along with HD-2 (Ru-complex of 4, 4?-bis-(1,4-benzodioxan-5-yl-vinyl)-[2,2?]bipyridine), displayed higher power conversion efficiencies (PCEs) than the device sensitized using only HD-2. In the present work, ruthenium based sensitizer, HD-2, has been chosen due to its better solar-to-power conversion efficiency and impressively higher photocurrent densities than that of standard N719. Among them, co-adsorber DBA-2, containing barbituric acid as the acceptor/anchoring group displays promising photovoltaic results and exhibited an enhanced efficiency of 8.06%. Further, good agreement between the calculated and experimental results showcase the precision of the energy functional and basis set utilized in this study. All these findings provide a deeper insight and better understanding into the intricacies involved in the design of superior co-sensitizers for development of highly efficient DSSCs. © 2016 Elsevier Ltd. All rights reserved.Item New carbazole based metal-free organic dyes with D-?-A-?-A architecture for DSSCs: Synthesis, theoretical and cell performance studies(Elsevier Ltd, 2017) Naik, P.; Elmorsy, M.R.; Su, R.; Babu, D.D.; El-Shafei, A.; Vasudeva Adhikari, A.V.Herein we report the design, synthesis and photovoltaic performance studies of three new D-?-A-?-A architectured organic chromophores (N1-3) derived from (Z)-3-(9-hexyl-9H-carbazol-3-yl)-2-(thiophen-2-yl) acrylonitrile scaffold. In the new design, the electron rich carbazole unit is connected to three different electron withdrawing/anchoring species, viz. cyano acetic acid, rhodanine-3-acetic acid and barbituric acid via cyano vinyl thiophene as ?-spacer. Newly synthesized dyes were characterized by spectral, photophysical and electrochemical analyses. Their optical band-gap, GSOP and ESOP values, as calculated from the optical and CV studies were found to be in the range of 2.12–2.21, ?5.52 to ?5.43 and ?5.40 to ?3.25 eV respectively. The DFT and TD-DFT studies were performed using Turbomole 7.1V software and the results indicated the existence of proper charge separation between HOMO and LUMO levels of the dyes. Also, the results revealed good matching of theoretically generated optical spectral data with the experimental values. Finally, DSSC devices were fabricated using these three dyes and the dye N1 containing cyanoacetic acid as an acceptor unit showed better photo conversion efficiency (?) of 3.55% than the other two dyes. It's JSC, VOC, and IPCE parameters were shown to be 9.06 mA cm?2, 0.577 V and 48%, respectively. The obtained EIS data and electron lifetimes of N1–3 sensitized devices are well in accordance with experimental photovoltaic parameters. © 2017 Elsevier LtdItem Synthesis and photovoltaic performance of a novel asymmetric dual-channel co-sensitizer for dye-sensitized solar cell beyond 10% efficiency(Elsevier Ltd, 2017) Babu, D.D.; Su, R.; Naik, P.; El-Shafei, A.; Vasudeva Adhikari, A.V.In this paper, we report the design and synthesis of a new bi-anchoring indole based co-sensitizer DBA-8 with A-?-D-A (acceptor-? bridge-donor-acceptor) architecture, carrying indole moiety as a donor and barbituric acid as acceptor/anchoring groups. Its photo-physical and electrochemical properties along with molecular geometries, calculated from Density Functional Theory (DFT) are employed to comprehend the effect of co-sensitizer structure on photovoltaic characteristics of DSSCs. The abovementioned organic dye (DBA-8) was employed as a co-sensitizer along with well-known ruthenium based sensitizer NCSU-10 in order to broaden the spectral responses of the co-sensitized DSSC. In the present work, for the first time we are demonstrating the profound role of a dual-anchoring co-sensitizer that can play in ameliorating the overall performance of a solar cell. The photovoltaic studies indicated that, the co-sensitizer DBA-8 succeeded in increasing the light harvesting ability in the device significantly. Notably, the device co-sensitized using 0.2 mM DBA-8 along with ruthenium based chromophore NCSU-10, showed a maximum efficiency of 10.68% (Jsc = 25.14 mAcm?2, Voc = 0.695 V, ff = 61.2%). Further, the good agreement between the theoretically and experimentally obtained ?max data vindicate that, the energy functional and basis set employed in this study can be successfully utilized for predicting the absorption spectra of new photosensitizers, with great precision before synthesis. Furthermore, all these findings showcase the vast potential of bi-anchoring molecules in improving the overall performance of the dye-sensitized solar cells. © 2017 Elsevier LtdItem Investigation of new carbazole based metal-free dyes as active photo-sensitizers/co-sensitizers for DSSCs(Elsevier Ltd, 2018) Naik, P.; Su, R.; Elmorsy, M.R.; El-Shafei, A.; Vasudeva Adhikari, A.V.Herein, we report the molecular design, synthesis and characterization of three new D-D-?-A configured metal-free chromophores D1-3 for their application in DSSCs as sensitizers as well as co-sensitizers. The new entities comprise carbazole as donor scaffold, 4-methoxyphenyl group as auxiliary donor and three different units, viz. cyanoacetic acid, 2, 4-thiazolidinedione and barbituric acid as acceptor/anchoring groups. Their photochemical, electrochemical and theoretical studies were carried out in order to assess their feasibility as active sensitizers. Further, D1-3 were exploited as co-sensitizers along with NCSU-10 dye. Their photoelectrochemical performances and charge transport properties in fabricated DSSCs were studied. The results revealed that D1 sensitizer displayed the highest PCE of 2.20% among the three dyes. D3 when co-sensitized with NCSU-10 displayed an improved PCE of 8.32% (JSC = 19.25 mA.cm?2, VOC = 0.680 V, FF = 63.7%) while NCSU-10 alone exhibited PCE of 8.25% (JSC = 20.41 mA.cm?2, VOC = 0.667 V, FF = 60.6%). © 2017 Elsevier LtdItem New carbazole based dyes as effective co-sensitizers for DSSCs sensitized with ruthenium (II) complex (NCSU-10)(Elsevier B.V., 2018) Naik, P.; Su, R.; Elmorsy, M.R.; El-Shafei, A.; Vasudeva Adhikari, A.V.Herein, we report the design and synthesis of three new D–A type metal-free carbazole based dyes (S1–3) as effective co-sensitizers for dye-sensitized solar cell (DSSC) sensitized with Ru(II) complex (NCSU-10). In this new design, the electron rich carbazole unit was attached to three different electron withdrawing/anchoring species, viz. 4-amino benzoic acid, sulfanilic acid and barbituric acid. The dyes were characterized by spectral, photophysical and electrochemical analysis. Their optical and electrochemical parameters along with molecular geometries, optimized from DFT have been employed to apprehend the effect of the structures of these co-sensitizers on the photovoltaic performances. Further, S1–3 dyes were co-sensitized along with a well-known NCSU-10 dye in order to broaden the spectral response of the co-sensitized devices and hence improve the efficiency. The photovoltaic performance studies indicated that, the device fabricated using S1 dye as co-sensitizer with 0.2 mM of NCSU-10 exhibited improved PCE of 9.55% with JSC of 22.85 mA cm?2, VOC of 0.672 V and FF of 62.2%, whereas the DSSC fabricated with dye NCSU-10 (0.2 mM) alone displayed PCE of 8.25% with JSC of 20.41 mA cm?2, VOC of 0.667 V and FF of 60.6%. Furthermore, electronic excitations simulated using time-dependent DFT, were in good agreement with the experimentally obtained results of the co-sensitizers, indicating that the exchange-correlation function and basis set utilized for predicting the spectra of the co-sensitizers are quite appropriate for the calculations. In conclusion, the results showed the potential of simple organic co-sensitizers in the development of efficient DSSCs. © 2017 Science PressItem Highly efficient carbazole based co-sensitizers carrying electron deficient barbituric acid for NCSU-10 sensitized DSSCs(Elsevier Ltd, 2018) Naik, P.; Keremane, K.S.; Elmorsy, M.R.; Su, R.; El-Shafei, A.; Vasudeva Adhikari, A.V.Herein, we report a comparative study of four interesting metal-free carbazole based organic dyes with different structural configurations, carrying electron deficient barbituric acid (C1-4), as effective co-sensitizers in DSSCs sensitized with NCSU-10 dye. The new entities comprise different structural architectures, viz. D-A (C1), D-?-A (C2), D-D-?-A (C3) and D-A-?-A (C4) configurations with same accepting/anchoring moiety. They consist of carbazole as donor scaffold linked to barbituric acid as an acceptor/anchoring unit via different ?-spacers. This paper describes the study of all the four co-sensitizers with regard to their structural, photophysical, electrochemical, theoretical and photovoltaic investigations. Also, it includes their structure-performance correlation study in detail. The devices co-sensitized with C1-4 displayed the superior photovoltaic performance when compared to NCSU-10 alone. The results ameliorate the role of efficient co-sensitizers to yield DSSC with improved performance. © 2018 Elsevier Ltd