Browsing by Author "El-Shafei, A."

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An Efficient Aniline-Based Co-Sensitizer for High Performance N3-Sensitized Solar Cells
(Wiley-Blackwell info@wiley.com, 2018) Naik, P.; Abdellah, I.M.; Abdel-Shakour, M.; Acharaya, M.; Pilicode, N.; El-Shafei, A.; Vasudeva Adhikari, A.V.
In this work, we report a comprehensive photovoltaic investigation of a structurally simple Donor-Acceptor (D?A) configured organic dye, N,N-PABA as an active co-sensitizer in DSSCs sensitized with well-known Ru (II) based N3 dye. This effective co-sensitizer (N,N-PABA) comprises N,N-dimethylaniline system as a donor scaffold linked with 4-aminobenzoic acid as an electron withdrawing functionality. In the present study, we have demonstrated the profound effect of concentration of sensitizer, i. e. N3 based dye as well as co-sensitizer, i. e. N,N-PABA on the photovoltaic performance characteristics of solar cells. Interestingly, the best photovoltaic performance was obtained for the co-sensitized device fabricated using 0.2 mM of N,N-PABA along with 0.3 mM of N3 sensitizer, in presence of 20 mM of CDCA. It displayed power conversion efficiency (PCE) of 5.82% with JSC of 14.35 mA.cm?2, VOC of 0.626 V and FF of 64.85%. Here, the N,N-PABA effectively filled the absorption valley, avoided the dye aggregation and reduced the charge recombination in the co-sensitized devices. Thus, the results ameliorate the role of efficient co-sensitizers to yield DSSC with improved performance by the selection of a matchable co-sensitizer at an appropriate concentration. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Asymmetric Dual Anchoring Sensitizers/Cosensitizers for Dye Sensitized Solar Cell Application: An Insight into Various Fundamental Processes inside the Cell
(American Chemical Society service@acs.org, 2019) Kesavan, R.; Attia, F.; Su, R.; Anees, P.; El-Shafei, A.; Vasudeva Adhikari, A.V.
To study the various fundamental processes occurring inside the dye sensitized solar cell (DSSC), we have fabricated devices employing newly synthesized diphenylamine-based organic dyes with A-D-?-A configuration, carrying four different anchoring groups, namely, cyanoacetic acid (DDC), rhodanine acetic acid (DDR), 4-hydrazinylbenzoic acid (DDH), and barbituric acid (DDB), as effective sensitizers/cosensitizers. In the present work, all the bianchoring dyes were subjected to photophysical, electrochemical, thermodynamic, photoelectrochemical, and theoretical studies. All of them displayed characteristic ?abs and ?emi in the range of 415-480 and 570-680 nm, respectively. Their optical and electrochemical band gaps were calculated to be in the order of 2.1 to 2.3 eV. The calculated driving forces for electron injection (?Ginj), recombination (?Ginj), and regeneration (?Greg) processes were found to be negative, showing the feasibility of these processes, while their DFT studies clearly indicated the directional flow of electrons within the dye in the cell. The devices with DDC as sensitizer displayed the highest conversion efficiency of 2.53%, whereas DDB exhibited the maximum of 7.69% when employed as a cosensitizer along with Ru (II) based HD-2 dye. Finally, EIS circuit fitting was carried out in order to obtain different interface resistance values to study the fundamental processes of energy conversion. © © 2019 American Chemical Society.
Carbazole based organic dyes as effective photosensitizers: A comprehensive analysis of their structure-property relationships
(John Wiley and Sons Inc, 2022) Naik, P.; Keremane, K.S.; Elmorsy, M.R.; El-Shafei, A.; Vasudeva Adhikari, A.V.
The present work describes the effect of structural modification of carbazole-based photosensitizers carrying carboxylic acid as a common anchoring functionality, on the photovoltaic parameters of newly fabricated DSSCs. In this study, we have selected our previously reported three carbazole-based derivatives, viz. S1-3 having different structural designs, that is, D-π-A (S1), D-D-π-A (S2), and A-π-D-π-A (S3) with different donor units and π-spacers, but an identical cyanoacetic acid anchoring unit. We have evaluated their optical, electrochemical, and photovoltaic behaviors in order to explore their structure-property relationships. Also, the theoretical investigations were performed to obtain a deeper understanding of their HOMO-LUMO levels, charge distribution in FMOs, directional flow of electrons within the push-pull type sensitizers, and optical behavior. Finally, the DSSCs were constructed by employing these dyes as sensitizers without any co-absorbents and the performance of the devices was evaluated by using illuminated current-voltage characteristics. Among the tested dyes, di-anchoring S3 exhibited improved PCE of 3.77 % due to its strong adsorption on the TiO2 surface that resulted in superior VOC of the cell. While the S2 containing electron-releasing anisole as an auxiliary donor exhibited better JSC value leading to the optimum PCE of 3.73 % which is comparable to that of S3. Obviously, these results validate the role of the π-spacer and additional donor of the sensitizers on the overall performance of the DSSCs. © 2021 The Authors. Electrochemical Science Advances published by Wiley-VCH GmbH.
Enhancing photovoltaic performance of DSSCs sensitized with Ru-II complexes by D-?-A configured carbazole based co-sensitizers
(Royal Society of Chemistry, 2018) Naik, P.; Elmorsy, M.R.; Su, R.; El-Shafei, A.; Vasudeva Adhikari, A.
Herein, we report the photovoltaic performance studies of four D-?-A configured carbazole based co-sensitizers, P1-4, in DSSCs sensitized with Ru-II complexes, i.e.NCSU-10/N3. The organic co-sensitizers (P1-4) comprise carbazole as a donor scaffold, a phenylene ring as a ?-spacer and electron withdrawing functional groups, viz. cyanoacetic acid (P1), rhodanine-3-acetic acid (P1-2), barbituric acid (P3), and thiobarbituric acid (P4) as acceptor/anchoring units. From the results, it is evident that the device fabricated using co-sensitizer P1 carrying cyanoacetic acid, at the concentration of 0.2 mM NCSU-10, exhibited an enhanced photon conversion efficiency (PCE) of 9.19% with a JSC of 21.20 mA cm-2, VOC of 0.658 V and FF of 65.85%, while P3 containing barbituric acid displayed a PCE of 8.75% with a JSC of 22.23 mA cm-2, VOC of 0.671 V and FF of 58.64%, whereas NCSU-10 (0.2 mM) alone displayed a PCE of 8.28% with a JSC of 20.38 mA cm-2, VOC of 0.665 V and FF of 61.09%, but the dyes P2 carrying rhodanine-3-acetic acid and P4 containing thiobarbituric acid showed considerably lower performance. The co-sensitized devices of N3 with P1-4 displayed inferior photovoltaic performance compared to N3 itself, probably due to inefficient suppression of back current. The observed results have thrown new light upon the selection of appropriate and matchable co-sensitizers for improving photovoltaic performance of Ru-II based sensitizers. © 2018 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
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.
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
Highly efficient panchromatic dye-sensitized solar cells: Synergistic interaction of ruthenium sensitizer with novel co-sensitizers carrying different acceptor units
(Elsevier Ltd, 2016) Babu, D.D.; Elsherbiny, D.; Cheema, H.; El-Shafei, A.; Vasudeva Adhikari, A.V.
Herein, we report the molecular design, synthesis and photovoltaic performance studies of three new organic co-sensitizers, N1-3 carrying indole and thiophene units linked to different acceptors/anchoring groups, as co-adsorbents for dye sensitized solar cells. We present the role of anchoring/acceptor units on co-sensitization properties N1-3. Their photo-physical and electrochemical results along with molecular geometry, obtained from Density Functional Theory are utilized to rationalize the influence of co-sensitizer structures on photovoltaic properties for DSSCs. We have shown that, the co-sensitization effect is profoundly dependent upon the anchoring/acceptor unit in the co-adsorbents. Among them, N3 containing 4-aminobenzoic acid shows promising co-sensitization results and exhibits an enhanced efficiency of 9.26%, when co-sensitized with a ruthenium dye, HD-14. Further, the study highlights the importance of molecular matching between the sensitizer and co-sensitizer in enhancing the efficiency. Furthermore, vertical electronic excitations are calculated using time dependent density functional theory studies. © 2016 Elsevier Ltd. All rights reserved.
Improved photovoltaic performances of Ru (II) complex sensitized DSSCs by co-sensitization of carbazole based chromophores
(Elsevier B.V., 2017) Naik, P.; Su, R.; El-Shafei, A.; Vasudeva Adhikari, A.
Herein, we report photovoltaic performance studies of three carbazole based dyes (N1–3) derived from (Z)-3-(9-hexyl-9H-carbazol-3-yl)-2-(thiophen-2-yl)acrylonitrile scaffold as effective co-sensitizers in Ru (II) complex, i.e. NCSU-10 sensitized DSSCs. From the results it is evident that, the device fabricated using co-sensitizer N3 with 0.2 mM of NCSU-10 exhibited improved photon conversion efficiency (PCE) of 8.73% with JSC of 19.87 mA·cm? 2, VOC of 0.655 V and FF of 67.0%, while N1 displayed PCE of 8.29% with JSC of 19.75 mA·cm? 2, VOC of 0.671 V and FF of 62.6%, whereas 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%. However, their EIS studies confirm that, N1, showing higher VOC is efficient in suppressing the undesired charge recombination in DSSCs through enhanced surface coverage on TiO2 and thereby resulting in longer electron lifetime than that of NCSU-10 dye alone. Here, the higher PCE of N3 can be attributed to its improved light harvesting efficiency, which is due to the presence of highly electron withdrawing barbituric acid in its structure. Conclusively, the results showcase the potential of simple carbazole based dyes as co-sensitizers in improving efficiency of DSSCs. © 2017
Improvement in performance of N3 sensitized DSSCs with structurally simple aniline based organic co-sensitizers
(Elsevier Ltd, 2018) Naik, P.; Abdellah, I.M.; Abdel-Shakour, M.; Su, R.; Keremane, K.S.; El-Shafei, A.; Vasudeva Adhikari, A.V.
In this work, we report comprehensive photovoltaic investigation of four structurally simple D-A configured organic dyes, A1-4 as active co-sensitizers in DSSCs sensitized with well-known Ru (II) based N3 dye. These effective co-sensitizers (A1-4) comprise N,N-dimethylaniline ring as donor scaffold linked with electron withdrawing functionalities, viz. barbituric acid (A1), N,N-dimethyl barbituric acid (A2), thiobarbituric acid (A3), and N,N-diethyl thiobarbituric acid (A4) as acceptor/anchoring units. In the present study, for the first time we have demonstrated the profound role of various simple organic molecules carrying different heterocyclic anchoring units on the photovoltaic parameters of the N3 sensitized devices. Also, the effect of concentration of sensitizer/co-sensitizers on the device performance characteristics has been investigated in depth. From the results, it is evident that, the device fabricated using co-sensitizer A2 carrying N,N-dimethyl barbituric acid along with sensitizer N3 in all concentrations outperformed when compared to N3 alone or other co-sensitizers. Interestingly, the best photovoltaic performance was obtained for the co-sensitized device fabricated using 0.3 mM co-sensitizer A2 along with 0.2 mM of N3 sensitizer. It displayed PCE of 7.02% with JSC of 15.27 mA·cm?2, VOC of 0.671 V and FF of 68.47%. Thus, the observed results have thrown new light upon the device optimization to yield DSSCs with improved performance by the selection of matchable co-sensitizers at appropriate concentrations. © 2018 Elsevier Ltd
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 Ltd
Molecular design and theoretical investigation of new metal-free heteroaromatic dyes with D-?-A architecture as photosensitizers for DSSC application
(Elsevier B.V., 2017) Naik, P.; Su, R.; Elmorsy, M.R.; Babu, D.D.; El-Shafei, A.; Vasudeva Adhikari, A.
Herein, we report design, synthesis and photovoltaic performance of four new metal-free heteroaromatic dyes (P1-4) with D-?-A architecture carrying electron donating carbazole core connected to four different electron withdrawing/anchoring groups, viz. cyanoacetic acid, rhodanine-3-acetic acid, barbituric acid and thiobarbituric acid and phenylene ring as a ?-spacer. The newly designed P1-4 were synthesized from carbazole derivative using Suzuki cross coupling approach followed by Knoevenagel condensation reaction. Their structures were confirmed by FTIR, NMR, Mass spectral and elemental analyses. The dyes were subjected to optical and electrochemical studies in order to investigate their absorption/emission behavior as well as HOMO/LUMO energies. The UV–vis spectral studies reveal that the P1-4 showed ?max at 412, 439, 458 and 489 nm, respectively. Their optical band-gap is in the range of 2.17 to 2.61 eV and fluorescence quantum yield is in the order of 44–70%. From energy level diagram, it is clear that all the dyes possess good thermodynamic feasibility for electron injection into CB edge of TiO2 as well as their regeneration from electrolyte system. The photovoltaic performance studies indicate that among the tested dyes, P1 anchored with cyanoacetic acid displayed the highest IPCE (32%), resulting in improved PCE (1.94%), JSC (4.68 mA cm?2), VOC (0.588 V) and FF (70.3%) values, when compared to other dyes. Finally, DFT studies were performed using Turbomole 7.1 V software to investigate their electron cloud delocalization in HOMO/LUMO levels and theoretical absorption spectral data. The results reveal that the dye P1 showed effective charge separation in its FMO levels, which has reflected in its ICT behavior and hence P1 displayed the improved photovoltaic performance. © 2017 Elsevier B.V.
Molecular Engineering and Theoretical Investigation of Novel Metal-Free Organic Chromophores for Dye-Sensitized Solar Cells
(Elsevier Ltd, 2015) Babu, D.D.; Cheema, H.; Elsherbiny, D.; El-Shafei, A.; Vasudeva Adhikari, A.V.
In this work we report design and synthesis of three new metal free D-D-A-?-A type dyes (E1-3) with different acceptor/anchoring groups, as effective sensitizers for nanocrystalline titanium dioxide based dye sensitized solar cells. All the three dyes carry electron donating methoxy group as an auxiliary and indole as a principal donor, cyanovinylene as an auxiliary acceptor and thiophene as a ?-spacer. Whereas, cyanoacetic acid, rhodanine-3-acetic acid and 4-aminobenzoic acid perform as acceptor/anchoring moieties, respectively in the dyes E1-3. Though the dye containing 4-aminobenzoic acid unit (E3) exhibits comparatively lower ?max, it shows the highest power conversion efficiency arising from the higher electron life time and good light-harvesting capability. The DFT studies reveal a better charge separation between the HOMO and LUMO levels of E3, further substantiating the experimental results. Among the three dyes, E3 shows the best photovoltaic performance with short-circuit current density (Jsc) of 9.35 mA cm-2, open-circuit voltage (Voc) of 620 mV and fill factor (FF) of 0.71, corresponding to an overall conversion efficiency of 4.12% under standard global AM 1.5G. © 2015 Elsevier Ltd. All rights reserved.
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 Press
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 Ltd
New di-anchoring A-?-D-?-A configured organic chromophores for DSSC application: Sensitization and co-sensitization studies
(Royal Society of Chemistry, 2018) Naik, P.; Su, R.; Elmorsy, M.R.; El-Shafei, A.; Vasudeva Adhikari, A.
Herein, we report the design and synthesis of three new un-symmetrical metal-free carbazole based organic dyes, E1-3 with A-?-D-?-A architecture, as effective di-anchoring sensitizers in DSSCs. The new entities comprise carbazole as a donor scaffold connected to three different units, viz. cyano acetic acid, 2,4-thiazolidinedione and barbituric acid as acceptor/anchoring units via vinylene and phenylene as ?-spacers at 3- and 6-positions of the carbazole ring, respectively. Photophysical, electrochemical and theoretical studies were carried out in order to assess their feasibility as active sensitizers. Furthermore, their photoelectrochemical performances and charge transport properties in fabricated DSSCs were evaluated. The results revealed that the device fabricated with the E1 sensitizer displayed the highest PCE of 2.38% among the three dyes. Its JSC, VOC, and IPCE values were found to be 6.36 mA cm-2, 0.599 V, and 57%, respectively. Its enhanced performance is attributed to the presence of a highly electron withdrawing cyano acetic acid unit on either side of the carbazole core through appropriate ?-spacers. Interestingly, the DFT study indicated that the electron cloud of the LUMO level has been shifted significantly towards the 2-cyano phenyl acrylic acid connected at the 6th position of the carbazole ring, when compared to the cyano acrylic acid linked at position 3, confirming efficient charge separation in E1. The assigned lifetimes of E1-3 obtained from EIS studies were found to be in accordance with experimentally obtained photovoltaic parameters. Furthermore, E1-3, when co-sensitized with NCSU-10 sensitizer in DSSCs, displayed higher VOC values, but lower PCE values than that of NCSU-10. © 2018 The Royal Society of Chemistry and Owner Societies.
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 2016
Simple diphenylamine based D-?-A type sensitizers/co-sensitizers for DSSCs: A comprehensive study on the impact of anchoring groups
(Royal Society of Chemistry, 2019) Kesavan, R.; Abdellah, I.M.; Singh, S.P.; El-Shafei, A.; Vasudeva Adhikari, A.V.
Herein, we report the design, synthesis and characterization of a new series of simple donor-? spacer-acceptor/anchor (D-?-A) type diphenylamine based metal-free organic dyes possessing three different anchoring groups, viz. 4-aminobenzoic acid (DTP), 2-(4-nitrophenyl)acetonitrile (DTN), and barbituric acid (DTB), connected with 2-(thiophene-2-yl)-acetonitrile, as effective sensitizers and co-sensitizers in Dye Sensitized Solar Cells (DSSCs). They were subjected to photophysical, electrochemical and theoretical studies. The dyes exhibited characteristic ?abs and ?emi in the range of 445-485 and 545-570 nm, respectively. Both optical and electrochemical band gaps were found to be in the range of 2.2 to 2.35 eV. The driving forces for injection (?Ginj), recombination (?Grec) and regeneration (?Greg) processes were evaluated to understand their feasibility. Finally, the DSSC devices were fabricated employing the new dyes as sensitizers as well as co-sensitizers along with the Ru(ii) based N3 dye. Interestingly, DTP carrying 4-aminobenzoic acid as the anchoring group shows the best photoelectrochemical performance, viz. photovoltaic conversion efficiency (PCE) = 4.4%, open circuit potential (VOC) = 0.577 V, and short-circuit current density (JSC) = 9.06 mA cm-2 with a broad incident photon conversion efficiency (IPCE) spectrum. Co-sensitization of the dyes brought about enhanced VOC values, compared to the N3 dye alone. Finally, different interface resistance values obtained from the electrochemical impedance spectroscopy (EIS) circuit fitting were used to study the fundamental processes of energy conversion. © 2019 the Owner Societies.
Simple thiophene-bridged D-?-A type chromophores for DSSCs: a comprehensive study of their sensitization and co-sensitization properties
(Royal Society of Chemistry, 2020) Keremane, K.S.; Abdellah, I.M.; Naik, P.; El-Shafei, A.; Vasudeva Adhikari, A.V.
Herein, we report the design and synthesis of four new thiophene-bridged D-?-A configured organic dyes T1-4 comprising different donors, ?-spacers and anchoring units, as potential sensitizers and co-sensitizers for DSSCs. The current work also highlights their structural, photophysical, thermal, electrochemical, theoretical, and photoelectrochemical studies, including evaluation of their structure-property relationships. The optical results revealed that the dyes T1-4 display ?abs and ?emi in the range of 402-461 nm and 556-575 nm, respectively, with a bandgap in the order of 2.31-2.58 eV. Furthermore, the results showed that the dyes possess all the pre-requisites to act as sensitizers/co-sensitizers. Among the tested dyes, the device based on sensitizer T2 achieved the highest PCE compared to the other three dyes, under the standard conditions. Furthermore, their co-sensitized devices were fabricated by co-adsorbing them with the well-known Ru-based MH-12 sensitizer and interestingly the co-sensitizer T3 carrying an alkoxy group and a barbituric acid anchor displayed the highest PCE of 8.79%, which is much higher than that of MH-12 alone (8.18%). Conclusively, the study furnishes a deeper understanding of the intricacies involved in the structural modification of sensitizers/co-sensitizers in achieving an enhanced performance of the devices. This journal is © 2020 the Owner Societies.
Structurally simple D–A-type organic sensitizers for dye-sensitized solar cells: effect of anchoring moieties on the cell performance
(Springer Verlag service@springer.de, 2017) Naik, P.; Su, R.; Babu, D.D.; El-Shafei, A.; Vasudeva Adhikari, A.
Abstract: In this work, we report synthesis and device fabrication studies of four metal-free D–A-type dyes (A1–A4) based on structurally simple N,N-dimethyl-4-vinyl aniline carrying four different acceptor/anchoring groups, as sensitizers for sensitizing photoanode (TiO2). In the sensitizers, N,N-dimethylaniline ring acts as an electron donor, while barbituric acid, N,N-dimethyl barbituric acid, thiobarbituric acid and N,N-diethyl thiobarbituric acid function as electron acceptor/anchoring units. They were synthesized in good yield via Knoevenagel protocol in neutral condition without any catalyst. Further, they were subjected to structural, electrochemical and optical characterization in order to evaluate their structure, band gap and absorption/emission behavior. The studies reveal that all the four dyes have thermodynamic feasibility of electron injection as well as electron recombination; their optical band gaps were found to be in the range of 2.35–2.56 eV. High-quality crystals of A2 and A4 were grown by slow evaporation technique using its solution with 1:1 pet ether (60–80 °C)/ethyl acetate solvent mixture at room temperature. Their SC-XRD studies disclose that the crystals are in the triclinic system with space group P-1. Further, DFT studies were performed using Turbomole V7.1 software package to evaluate their optimized geometry and HOMO and LUMO levels. Finally, DSSC device fabricated with the dye A1 showed relatively good efficiency when compared to other dyes mainly due to the effective binding of barbituric acid on the surface of TiO2 through NH or OH functional group. Graphical Abstract: [Figure not available: see fulltext.]. © 2017, Iranian Chemical Society.
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 Ltd