Amaresh Mishra - Academia.edu (original) (raw)
Papers by Amaresh Mishra
Materials Advances
This review presents the development of solution-processed layer-by-layer (LBL) deposition as a p... more This review presents the development of solution-processed layer-by-layer (LBL) deposition as a promising technique for the fabrication of organic solar cells using fullerene/fullerene-free acceptors.
Advances in Polymer Science, 2017
Organic and hybrid bulk heterojunction (BHJ) solar cells are investigated. We describe the synthe... more Organic and hybrid bulk heterojunction (BHJ) solar cells are investigated. We describe the synthesis and solar cell characteristics of well-defined functional thiophene dendrimers. Three-dimensional morphologies of the polymer–metal oxide BHJs are analyzed with electron tomography and stochastic models, and are simulated with the latter, to establish the effect of processing on morphology. Device models based on stochastically simulated data of morphologies and transport parameters are used to provide accurate descriptions of solar cell performance.
ACS applied materials & interfaces, Jan 29, 2017
Two new donor-acceptor (D-A)-substituted S,N-heteroacene-based molecules were developed and inves... more Two new donor-acceptor (D-A)-substituted S,N-heteroacene-based molecules were developed and investigated as hole transporting material (HTM) for perovskite solar cells (PSC). Optical and electrochemical characterization brought out that the energy levels of both HTMs are suitable for their use in PSCs. Consequently, an impressive power-conversion efficiency of 17.7% and 16.1% was achieved from PSCs involving the HTM-1 and HTM-2, respectively. The optoelectronic properties in terms of series resistance, conductivity, and charge carrier recombination were further examined to unfold the potential of these new HTMs. Time-resolved photoluminescence spectroscopy brought out that the hole injection from the valence band of perovskite into HTMs follow the trend, which is in accordance with the position of the highest occupied molecular orbital. Overall, our findings underline the potential of S,N-heteroacene co-oligomers as promising HTM candidates for PSCs.
The Journal of Physical Chemistry C, 2013
Chemical Communications, 2013
General remarks: NMR spectra were recorded on a Bruker DRX 400 spectrometer (1 H NMR: 400 MHz, 13... more General remarks: NMR spectra were recorded on a Bruker DRX 400 spectrometer (1 H NMR: 400 MHz, 13 C NMR: 100 MHz). Chemical shift values (δ) are expressed in parts per million using residual solvent protons (1 H NMR, δ H = 7.26 for CDCl 3 ; 13 C NMR, δ C = 77.0 for CDCl 3) as internal standard. The splitting patterns are designated as follows: s (singlet), d (doublet), t (triplet) and m (multiplet). Elemental analyses were performed on an Elementar Vario EL. Melting points were determined using a Mettler Toledo DSC 823. Thin layer chromatography was carried out on aluminum plates, precoated with silica gel, Merck Si60 F254. Preparative column chromatography was performed on glass columns packed with silica gel, Merck Silica 60, particle size 40 − 63 μm. High performance liquid chromatography was performed on a Hitachi instrument equipped with a UV-vis detector L-7420, columns (Nucleosil 100-5 NO2 with a pore size of 100 Å) from Machery-Nagel using a dichloromethane/n-hexane mixture (40:60) as eluent. EI mass spectra were recorded on a Varian Saturn 2000 GC-MS, MALDI-MS experiments were performed using a MS Bruker Reflex 2 (Bruker Daltonik GmbH, Bremen, Germany) using trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB) as matrix. UV/Vis absorption spectra were recorded in 1 cm cuvettes with Merck Uvasol grade solvents on a Perkin Elmer Lambda 19 spectrometer. Cyclic voltammetry experiments were performed with a computer-controlled Autolab PGSTAT30 potentiostat in a three-electrode single-compartment cell with a platinum working electrode, a platinum wire counter electrode, and an Ag/AgCl reference electrode. All potentials were internally referenced to the ferrocene/ferrocenium couple. Surface images of the photoactive layers were recorded with the help of a Bruker Nanoscope V AFM at ambient temperature in tapping mode. Tetrahydrofuran and N,N-dimethylformamide (Merck) were absoluted via MB SPS-800 solvent purifying system (MBraun). Diisopropylamine (Merck) was absoluted over calcium hydride. All synthetic steps were carried out under argon atmosphere. n-Butyl lithium (1.6 mol/L in n-hexane) was purchased from Acros, trimethyltin chloride and 2-iso-propoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane were pur
Journal of Materials Chemistry A, 2016
Dithienopyrrole-based small molecular materials were developed achieving PCEs up to 5.3% in bulk-... more Dithienopyrrole-based small molecular materials were developed achieving PCEs up to 5.3% in bulk-heterojunction organic solar cells by the tuning of the alkyl substitution pattern and use of a solvent additive.
Journal of Photochemistry and Photobiology A: Chemistry, 1999
Advanced Functional Materials, 2012
Solar hydrogen generation sustained for at least several hours is demonstrated using a dye-sensit... more Solar hydrogen generation sustained for at least several hours is demonstrated using a dye-sensitised nickel(II) oxide photocathode and BiVO4 photoanode connected in a tandem configuration. H2 evolution rate is 120 nmol h−1 (>80% faradaic efficiency) without electrical bias or sacrificial oxidant/reductant, at pH = 7 using visible light (>420 nm).
3-Bromoacetylcoumarin-(2)obtained by brominationof 3-acetylcoumarin (1)was condensed with2-amin0-... more 3-Bromoacetylcoumarin-(2)obtained by brominationof 3-acetylcoumarin (1)was condensed with2-amin0-4-phenylthiazole,2-aminothiazole,2-aminobenzothiazole, 2- amino-4-phenyloxadiazole, 2-aminothiadiazole, 3-aminotriazole to form the corresponding heteroaryl aminoacetylcoumarins (3a-f).The reaction of 2 withthiourea furnished 2-amino-4-(coumarinyl-3) thiazole (4) which further reacted with phenyli$othiocyanate forming the unsymmetrical thiourea (5). The thiourea on cyclocondensation withchloroacetic acid gave the thiazolidinone (6)which on further reaction with differen~aromaUcaldehydes resulted inthe formationofthe corresponding arylidene compounds (7). The structures of the products were confirmed from their analytical and spectraldata.
ACS Applied Energy Materials
ACS Applied Materials & Interfaces
In recent years tremendous growth has been seen for solution-processed bulk heterojunction solar ... more In recent years tremendous growth has been seen for solution-processed bulk heterojunction solar cells (BHJSC) using fullerene-free molecular acceptors. Herein, we report the synthesis, characterization of a coumarin-based organic semiconducting molecule C1 and its use in BHJSCs as electron donor. The compound exhibited an absorption band at 472 nm in chloroform solution with optical energy gap of 2.33 eV. The HOMO/LUMO energy levels of C1 were found to be ideal for use in BHJSCs. Using PC71BM and a fullerene-free acceptor IT 4F the device generated power conversion efficiencies (PCE) of 6.17% and 8.31%, respectively. The success of device based on fullerene-free acceptor is a result of complementary absorption and well-matched energy levels, resulting in improved photocurrent and photovoltage in the device. Moreover, ternary solar cells fabricated by employing C1 (20 wt%) as secondary donor i.e. active layer of C1:PM6:IT-4F (0.2:0.8:1.5), generated enhanced PCE of 11.56% with a high short circuit current density (JSC) of 16.42 mA cm-2, open circuit voltage (VOC) of 1.02 V. and a fill factor of 0.69 under 1 sun spectral illumination, which is ~8% higher than that for the PM6:IT-4F based binary device (PCE = 10.70%). The increased PCE for the ternary OSC may be related to the efficient exciton generation and their dissociation via Forster resonance energy transfer which guarantees enough time for exciton to diffuse towards the D/A interfaces.
The Journal of Physical Chemistry C
A low bandgap D–D–A (D = donor; A = acceptor) type conjugated molecular triad TPA-SN5-DCV has bee... more A low bandgap D–D–A (D = donor; A = acceptor) type conjugated molecular triad TPA-SN5-DCV has been implemented in solution-processed organic solar cells using PC71BM as acceptor. The molecule showed a narrow optical energy gap of 1.59 eV, and a broad absorption spectrum ranging from 350 to 750 nm. Cyclic voltammetry measurements were used to estimate the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels and are −5.10 and −3.53 eV, respectively. After the optimization of the donor and acceptor (PC71BM) weight ratio, the device based on as cast TPA-SN5-DCV:PC71BM (1:2) active layer exhibited overall PCE of 3.34%, which was improved to 6.31% using 0.3 vol % 1,8-diiodooctane (DIO) as solvent additive (SA). Further optimization of the DIO-treated active layer via thermal annealing (TA) resulted in a markedly improved PCE of 7.26%. The enhancement in PCE after either SA or SA + TA treatment is largely accredited to the increase in both JSC and FF, which is associated with ...
The Journal of Physical Chemistry C
Dye-sensitized photocathodes have been observed on several occasions to sustain light-driven H 2 ... more Dye-sensitized photocathodes have been observed on several occasions to sustain light-driven H 2 generation without intentionally introduced catalysts. Herein, plausible mechanisms addressing this phenomenon are probed by a combination of long-term photoelectrochemical measurements with concurrent gas chromatography, transient absorption spectroscopy, and inductively coupled mass spectrometry using a perylenemonoimide-sexithiophene-triphenylamine (PMI-6T-TPA) sensitized NiO electrode. The experimental evidence obtained discounts the possibility for direct reduction of hydrogen by the dye and demonstrates that the availability of interfaces between dye molecules and any electrically disconnected NiO particles exposed to the electrolyte solution is critical for photoelectrocatalytic H 2 generation. These interfaces are postulated to serve as photoactive sites for the formation of a hydrogen evolution catalyst, e.g., metallic nickel, which can accept photogenerated electrons from the excited dye molecules. The Ni 0 catalyst can form via photoelectroreduction of Ni 2+ , which has been found to slowly dissolve from the NiO support into the solutions during the photoelectrochemical measurements. Additionally, dependence of the H 2 generation rate on the anion within the electrolyte has been identified, with the highest rates of 35-40 nmol h-1 cm-2 achieved with acetate. The origin of this dependence remains unsolved at this stage but is clearly demonstrated to be not associated with the different rates of dissolution of NiO, the presence of other transition metal contaminants, nor electronic impacts of the anion on the NiO valence band. Overall, the results herein demonstrate that the effects of the chemical nature of the electrolyte, metallic nickel deposited from dissolved Ni 2+ , and availability of the interfaces between disconnected NiO and adsorbed dye should be considered when interpreting the photoelectrocatalytic performance of dye-sensitized photocathodes for dihydrogen evolution.
J. Mater. Chem. A
Non-fullerene molecular acceptors in combination with a polymeric donor gave well performing BHJS... more Non-fullerene molecular acceptors in combination with a polymeric donor gave well performing BHJSCs with energy losses below 0.4 eV concomitant with outstanding external quantum efficiencies in the NIR-regime.
Encyclopedia of Supramolecular Chemistry, 2004
…, 2009
We report a new type of dendritic terthiophene attached to a 2,2&... more We report a new type of dendritic terthiophene attached to a 2,2'-bipyridine ligand for ruthenium-based dye-sensitized solar cells. As a result of the incorporation of this electron-rich terthiophene donor unit into the heteroleptic ruthenium sensitizer [Ru(dcbpy)(3Tbpy)(NCS)(2)] (3T), the lowest-energy metal-to-ligand charge transfer (MLCT) transition is red-shifted and the molar extinction coefficient is increased compared to the analogous standard Z907Na sensitizer. A preliminary investigation of the 3T dye in combination with an iodine/iodide-based electrolyte shows an interesting photovoltaic performance, with a maximum power conversion efficiency of 7.4 % measured under air mass 1.5 global sunlight irradiation. Accelerated testing of these devices at 60 degrees C under full sunlight soaking shows a remarkable stability over 1000 h.
Journal of Photochemistry …, 1998
... Center of Studies in Surface Science and Technology, Department of Chemistry, Sambalpur Unive... more ... Center of Studies in Surface Science and Technology, Department of Chemistry, Sambalpur University, Jyoti Vihar 768 019, India. Accepted 15 August 1997. Available online 27 April 1998. ... References. PK Dash, BK Mishra and GB Behera, Spectrochim. Acta A52 (1996), p. 349. ...
Journal of luminescence, 2001
Absorption, fluorescence emission spectra and fluorescence lifetimes of N-alkyl-4-(p-N,N-dimethyl... more Absorption, fluorescence emission spectra and fluorescence lifetimes of N-alkyl-4-(p-N,N-dimethyl aminostyryl) pyridinium dyes of varying lengths of alkyl chain have been measured in different organic solvents (protic, dipolar aprotic and aprotic) and in different surfactant solutions. The spectra for the dyes are similar in a single solvent but vary with solvent type. The Stokes shift for the dye does not vary with the solvent parameter as predicted by Lippert-Mataga equation. The fluorescence decay of the dyes shows two lifetimes in organic solvents except in a few solvents where a single or three lifetimes were obtained. The lifetime results are interpreted in terms of emission from cis and quinoid (or intramolecular charge transfer, ICT) forms of the dye in the excited state. The spectra and fluorescence lifetime results for the cis isomer (synthesized as a stable compound) in organic solvents confirmed the coexistence of multiple species. In surfactant solutions, the spectra and fluorescence lifetimes of the dyes depend upon the length of the alkyl chain of the dye and the concentration of the surfactant, namely, premicellar or post micellar. Dye-surfactant complexes were identified in a few cases in SDS and CTAB premicellar solutions. TX-100 surfactant is found to stabilize the cis isomer for all the dyes, whereas both SDS and CTAB surfactants stabilize the trans isomer predominantly.
Advanced Functional Materials, 2012
ABSTRACT The convergent synthesis of a series of acceptor–donor–acceptor (A-D-A) type dicaynoviny... more ABSTRACT The convergent synthesis of a series of acceptor–donor–acceptor (A-D-A) type dicaynovinyl (DCV)-substituted oligoselenophenes DCVnS (n = 3–5) is presented. Trends in thermal and optoelectronic properties are studied, in dependence on the length of the conjugated backbone. Optical measurements reveal red-shifted absorption spectra and electrochemical investigations show lowering of the lowest unoccupied molecular orbital (LUMO) energy levels for DCVnS compared to the corresponding thiophene analogs DCVnT. As a consequence, a lowering of the bandgap is observed. Single crystal X-ray structure analysis of tetramer DCV4S provides important insight into the packing features and intermolecular interactions of the molecules, further corroborating the importance of the DCV acceptor groups for the molecular ordering. DCV4S and DCV5S are used as donor materials in planar heterojunction (PHJ) and bulk-heterojunction (BHJ) organic solar cells. The devices show very high fill factors (FF), a high open circuit voltage, and power conversion efficiencies (PCE) of up to 3.4% in PHJ solar cells and slightly reduced PCEs of up to 2.6% in BHJ solar cells. In PHJ devices, the PCE for DCV4S almost doubles compared to the PCE reported for the oligothiophene analog DCV4T, while DCV5S shows an about 30% higher PCE than DCV5T.
Materials Advances
This review presents the development of solution-processed layer-by-layer (LBL) deposition as a p... more This review presents the development of solution-processed layer-by-layer (LBL) deposition as a promising technique for the fabrication of organic solar cells using fullerene/fullerene-free acceptors.
Advances in Polymer Science, 2017
Organic and hybrid bulk heterojunction (BHJ) solar cells are investigated. We describe the synthe... more Organic and hybrid bulk heterojunction (BHJ) solar cells are investigated. We describe the synthesis and solar cell characteristics of well-defined functional thiophene dendrimers. Three-dimensional morphologies of the polymer–metal oxide BHJs are analyzed with electron tomography and stochastic models, and are simulated with the latter, to establish the effect of processing on morphology. Device models based on stochastically simulated data of morphologies and transport parameters are used to provide accurate descriptions of solar cell performance.
ACS applied materials & interfaces, Jan 29, 2017
Two new donor-acceptor (D-A)-substituted S,N-heteroacene-based molecules were developed and inves... more Two new donor-acceptor (D-A)-substituted S,N-heteroacene-based molecules were developed and investigated as hole transporting material (HTM) for perovskite solar cells (PSC). Optical and electrochemical characterization brought out that the energy levels of both HTMs are suitable for their use in PSCs. Consequently, an impressive power-conversion efficiency of 17.7% and 16.1% was achieved from PSCs involving the HTM-1 and HTM-2, respectively. The optoelectronic properties in terms of series resistance, conductivity, and charge carrier recombination were further examined to unfold the potential of these new HTMs. Time-resolved photoluminescence spectroscopy brought out that the hole injection from the valence band of perovskite into HTMs follow the trend, which is in accordance with the position of the highest occupied molecular orbital. Overall, our findings underline the potential of S,N-heteroacene co-oligomers as promising HTM candidates for PSCs.
The Journal of Physical Chemistry C, 2013
Chemical Communications, 2013
General remarks: NMR spectra were recorded on a Bruker DRX 400 spectrometer (1 H NMR: 400 MHz, 13... more General remarks: NMR spectra were recorded on a Bruker DRX 400 spectrometer (1 H NMR: 400 MHz, 13 C NMR: 100 MHz). Chemical shift values (δ) are expressed in parts per million using residual solvent protons (1 H NMR, δ H = 7.26 for CDCl 3 ; 13 C NMR, δ C = 77.0 for CDCl 3) as internal standard. The splitting patterns are designated as follows: s (singlet), d (doublet), t (triplet) and m (multiplet). Elemental analyses were performed on an Elementar Vario EL. Melting points were determined using a Mettler Toledo DSC 823. Thin layer chromatography was carried out on aluminum plates, precoated with silica gel, Merck Si60 F254. Preparative column chromatography was performed on glass columns packed with silica gel, Merck Silica 60, particle size 40 − 63 μm. High performance liquid chromatography was performed on a Hitachi instrument equipped with a UV-vis detector L-7420, columns (Nucleosil 100-5 NO2 with a pore size of 100 Å) from Machery-Nagel using a dichloromethane/n-hexane mixture (40:60) as eluent. EI mass spectra were recorded on a Varian Saturn 2000 GC-MS, MALDI-MS experiments were performed using a MS Bruker Reflex 2 (Bruker Daltonik GmbH, Bremen, Germany) using trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB) as matrix. UV/Vis absorption spectra were recorded in 1 cm cuvettes with Merck Uvasol grade solvents on a Perkin Elmer Lambda 19 spectrometer. Cyclic voltammetry experiments were performed with a computer-controlled Autolab PGSTAT30 potentiostat in a three-electrode single-compartment cell with a platinum working electrode, a platinum wire counter electrode, and an Ag/AgCl reference electrode. All potentials were internally referenced to the ferrocene/ferrocenium couple. Surface images of the photoactive layers were recorded with the help of a Bruker Nanoscope V AFM at ambient temperature in tapping mode. Tetrahydrofuran and N,N-dimethylformamide (Merck) were absoluted via MB SPS-800 solvent purifying system (MBraun). Diisopropylamine (Merck) was absoluted over calcium hydride. All synthetic steps were carried out under argon atmosphere. n-Butyl lithium (1.6 mol/L in n-hexane) was purchased from Acros, trimethyltin chloride and 2-iso-propoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane were pur
Journal of Materials Chemistry A, 2016
Dithienopyrrole-based small molecular materials were developed achieving PCEs up to 5.3% in bulk-... more Dithienopyrrole-based small molecular materials were developed achieving PCEs up to 5.3% in bulk-heterojunction organic solar cells by the tuning of the alkyl substitution pattern and use of a solvent additive.
Journal of Photochemistry and Photobiology A: Chemistry, 1999
Advanced Functional Materials, 2012
Solar hydrogen generation sustained for at least several hours is demonstrated using a dye-sensit... more Solar hydrogen generation sustained for at least several hours is demonstrated using a dye-sensitised nickel(II) oxide photocathode and BiVO4 photoanode connected in a tandem configuration. H2 evolution rate is 120 nmol h−1 (>80% faradaic efficiency) without electrical bias or sacrificial oxidant/reductant, at pH = 7 using visible light (>420 nm).
3-Bromoacetylcoumarin-(2)obtained by brominationof 3-acetylcoumarin (1)was condensed with2-amin0-... more 3-Bromoacetylcoumarin-(2)obtained by brominationof 3-acetylcoumarin (1)was condensed with2-amin0-4-phenylthiazole,2-aminothiazole,2-aminobenzothiazole, 2- amino-4-phenyloxadiazole, 2-aminothiadiazole, 3-aminotriazole to form the corresponding heteroaryl aminoacetylcoumarins (3a-f).The reaction of 2 withthiourea furnished 2-amino-4-(coumarinyl-3) thiazole (4) which further reacted with phenyli$othiocyanate forming the unsymmetrical thiourea (5). The thiourea on cyclocondensation withchloroacetic acid gave the thiazolidinone (6)which on further reaction with differen~aromaUcaldehydes resulted inthe formationofthe corresponding arylidene compounds (7). The structures of the products were confirmed from their analytical and spectraldata.
ACS Applied Energy Materials
ACS Applied Materials & Interfaces
In recent years tremendous growth has been seen for solution-processed bulk heterojunction solar ... more In recent years tremendous growth has been seen for solution-processed bulk heterojunction solar cells (BHJSC) using fullerene-free molecular acceptors. Herein, we report the synthesis, characterization of a coumarin-based organic semiconducting molecule C1 and its use in BHJSCs as electron donor. The compound exhibited an absorption band at 472 nm in chloroform solution with optical energy gap of 2.33 eV. The HOMO/LUMO energy levels of C1 were found to be ideal for use in BHJSCs. Using PC71BM and a fullerene-free acceptor IT 4F the device generated power conversion efficiencies (PCE) of 6.17% and 8.31%, respectively. The success of device based on fullerene-free acceptor is a result of complementary absorption and well-matched energy levels, resulting in improved photocurrent and photovoltage in the device. Moreover, ternary solar cells fabricated by employing C1 (20 wt%) as secondary donor i.e. active layer of C1:PM6:IT-4F (0.2:0.8:1.5), generated enhanced PCE of 11.56% with a high short circuit current density (JSC) of 16.42 mA cm-2, open circuit voltage (VOC) of 1.02 V. and a fill factor of 0.69 under 1 sun spectral illumination, which is ~8% higher than that for the PM6:IT-4F based binary device (PCE = 10.70%). The increased PCE for the ternary OSC may be related to the efficient exciton generation and their dissociation via Forster resonance energy transfer which guarantees enough time for exciton to diffuse towards the D/A interfaces.
The Journal of Physical Chemistry C
A low bandgap D–D–A (D = donor; A = acceptor) type conjugated molecular triad TPA-SN5-DCV has bee... more A low bandgap D–D–A (D = donor; A = acceptor) type conjugated molecular triad TPA-SN5-DCV has been implemented in solution-processed organic solar cells using PC71BM as acceptor. The molecule showed a narrow optical energy gap of 1.59 eV, and a broad absorption spectrum ranging from 350 to 750 nm. Cyclic voltammetry measurements were used to estimate the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels and are −5.10 and −3.53 eV, respectively. After the optimization of the donor and acceptor (PC71BM) weight ratio, the device based on as cast TPA-SN5-DCV:PC71BM (1:2) active layer exhibited overall PCE of 3.34%, which was improved to 6.31% using 0.3 vol % 1,8-diiodooctane (DIO) as solvent additive (SA). Further optimization of the DIO-treated active layer via thermal annealing (TA) resulted in a markedly improved PCE of 7.26%. The enhancement in PCE after either SA or SA + TA treatment is largely accredited to the increase in both JSC and FF, which is associated with ...
The Journal of Physical Chemistry C
Dye-sensitized photocathodes have been observed on several occasions to sustain light-driven H 2 ... more Dye-sensitized photocathodes have been observed on several occasions to sustain light-driven H 2 generation without intentionally introduced catalysts. Herein, plausible mechanisms addressing this phenomenon are probed by a combination of long-term photoelectrochemical measurements with concurrent gas chromatography, transient absorption spectroscopy, and inductively coupled mass spectrometry using a perylenemonoimide-sexithiophene-triphenylamine (PMI-6T-TPA) sensitized NiO electrode. The experimental evidence obtained discounts the possibility for direct reduction of hydrogen by the dye and demonstrates that the availability of interfaces between dye molecules and any electrically disconnected NiO particles exposed to the electrolyte solution is critical for photoelectrocatalytic H 2 generation. These interfaces are postulated to serve as photoactive sites for the formation of a hydrogen evolution catalyst, e.g., metallic nickel, which can accept photogenerated electrons from the excited dye molecules. The Ni 0 catalyst can form via photoelectroreduction of Ni 2+ , which has been found to slowly dissolve from the NiO support into the solutions during the photoelectrochemical measurements. Additionally, dependence of the H 2 generation rate on the anion within the electrolyte has been identified, with the highest rates of 35-40 nmol h-1 cm-2 achieved with acetate. The origin of this dependence remains unsolved at this stage but is clearly demonstrated to be not associated with the different rates of dissolution of NiO, the presence of other transition metal contaminants, nor electronic impacts of the anion on the NiO valence band. Overall, the results herein demonstrate that the effects of the chemical nature of the electrolyte, metallic nickel deposited from dissolved Ni 2+ , and availability of the interfaces between disconnected NiO and adsorbed dye should be considered when interpreting the photoelectrocatalytic performance of dye-sensitized photocathodes for dihydrogen evolution.
J. Mater. Chem. A
Non-fullerene molecular acceptors in combination with a polymeric donor gave well performing BHJS... more Non-fullerene molecular acceptors in combination with a polymeric donor gave well performing BHJSCs with energy losses below 0.4 eV concomitant with outstanding external quantum efficiencies in the NIR-regime.
Encyclopedia of Supramolecular Chemistry, 2004
…, 2009
We report a new type of dendritic terthiophene attached to a 2,2&... more We report a new type of dendritic terthiophene attached to a 2,2'-bipyridine ligand for ruthenium-based dye-sensitized solar cells. As a result of the incorporation of this electron-rich terthiophene donor unit into the heteroleptic ruthenium sensitizer [Ru(dcbpy)(3Tbpy)(NCS)(2)] (3T), the lowest-energy metal-to-ligand charge transfer (MLCT) transition is red-shifted and the molar extinction coefficient is increased compared to the analogous standard Z907Na sensitizer. A preliminary investigation of the 3T dye in combination with an iodine/iodide-based electrolyte shows an interesting photovoltaic performance, with a maximum power conversion efficiency of 7.4 % measured under air mass 1.5 global sunlight irradiation. Accelerated testing of these devices at 60 degrees C under full sunlight soaking shows a remarkable stability over 1000 h.
Journal of Photochemistry …, 1998
... Center of Studies in Surface Science and Technology, Department of Chemistry, Sambalpur Unive... more ... Center of Studies in Surface Science and Technology, Department of Chemistry, Sambalpur University, Jyoti Vihar 768 019, India. Accepted 15 August 1997. Available online 27 April 1998. ... References. PK Dash, BK Mishra and GB Behera, Spectrochim. Acta A52 (1996), p. 349. ...
Journal of luminescence, 2001
Absorption, fluorescence emission spectra and fluorescence lifetimes of N-alkyl-4-(p-N,N-dimethyl... more Absorption, fluorescence emission spectra and fluorescence lifetimes of N-alkyl-4-(p-N,N-dimethyl aminostyryl) pyridinium dyes of varying lengths of alkyl chain have been measured in different organic solvents (protic, dipolar aprotic and aprotic) and in different surfactant solutions. The spectra for the dyes are similar in a single solvent but vary with solvent type. The Stokes shift for the dye does not vary with the solvent parameter as predicted by Lippert-Mataga equation. The fluorescence decay of the dyes shows two lifetimes in organic solvents except in a few solvents where a single or three lifetimes were obtained. The lifetime results are interpreted in terms of emission from cis and quinoid (or intramolecular charge transfer, ICT) forms of the dye in the excited state. The spectra and fluorescence lifetime results for the cis isomer (synthesized as a stable compound) in organic solvents confirmed the coexistence of multiple species. In surfactant solutions, the spectra and fluorescence lifetimes of the dyes depend upon the length of the alkyl chain of the dye and the concentration of the surfactant, namely, premicellar or post micellar. Dye-surfactant complexes were identified in a few cases in SDS and CTAB premicellar solutions. TX-100 surfactant is found to stabilize the cis isomer for all the dyes, whereas both SDS and CTAB surfactants stabilize the trans isomer predominantly.
Advanced Functional Materials, 2012
ABSTRACT The convergent synthesis of a series of acceptor–donor–acceptor (A-D-A) type dicaynoviny... more ABSTRACT The convergent synthesis of a series of acceptor–donor–acceptor (A-D-A) type dicaynovinyl (DCV)-substituted oligoselenophenes DCVnS (n = 3–5) is presented. Trends in thermal and optoelectronic properties are studied, in dependence on the length of the conjugated backbone. Optical measurements reveal red-shifted absorption spectra and electrochemical investigations show lowering of the lowest unoccupied molecular orbital (LUMO) energy levels for DCVnS compared to the corresponding thiophene analogs DCVnT. As a consequence, a lowering of the bandgap is observed. Single crystal X-ray structure analysis of tetramer DCV4S provides important insight into the packing features and intermolecular interactions of the molecules, further corroborating the importance of the DCV acceptor groups for the molecular ordering. DCV4S and DCV5S are used as donor materials in planar heterojunction (PHJ) and bulk-heterojunction (BHJ) organic solar cells. The devices show very high fill factors (FF), a high open circuit voltage, and power conversion efficiencies (PCE) of up to 3.4% in PHJ solar cells and slightly reduced PCEs of up to 2.6% in BHJ solar cells. In PHJ devices, the PCE for DCV4S almost doubles compared to the PCE reported for the oligothiophene analog DCV4T, while DCV5S shows an about 30% higher PCE than DCV5T.