Chedarampet Karthikeyan | The Dow Chemical Company (original) (raw)

Papers by Chedarampet Karthikeyan

Laine/Ceramic, 2012

The nature and micro-structure of titania plays an important role in determining the overall effi... more The nature and micro-structure of titania plays an important role in determining the overall efficiency of the solar cell. The influence of three different nanocrystalline titania, prepared from three different routes, namely sol-gel, thermal, and colloidal-microwave process, on the performance of solid state dye sensitized solar cells was studied and reported here. The difference in the preparation of nanomaterials leads to different surface area, pore size and morphology of the mesoporous films. A methodical investigation on how such films with different structure and morphology affect the performance of solid-state dye sensitized solar cell is reported and discussed in this article. To support an investigation of this nature, XRD, BET, and scanning electron microscopy (SEM) were utilzed to have a clear understanding of the actual structure and morphology of mesoporous titania films applied in solid state DSSC. The work clearly demonstrates the optimal pore and morphological structures required for efficient functioning of solid-state dye sensitized solar cell.

Nano Energy, 2012

A new heteroleptic ruthenium(II) complex cis-di(thiocyanato)(4,4 0-dicarboxylic acid-2,2 0bipyrid... more A new heteroleptic ruthenium(II) complex cis-di(thiocyanato)(4,4 0-dicarboxylic acid-2,2 0bipyridine)(4,4 0-bis[(triethylene glycol methyl ether)(ditolylamine phenyl)ethenyl]-2,2 0-bipyridine) ruthenium(II) (Ru-TPA-EO-NCS) was synthesized and characterized as a sensitizer for dyesensitized solar cell application. The ligand contributes to enhance the light harvesting yield rendering a high short-circuit current density of 18.3 mA/cm 2 at full sun condition (1000 W/m 2) leading to an efficient dye-sensitized solar cell. The dye is explored for solid-state solar cell based on 2.0 mm thick thin TiO 2 film with organic hole transport material, Spiro-MeOTAD and it turns out to render 3.3% at full sun. The stability of DSCs is an important aspect for their commercialization. In this respect, the dye in conjunction with a solvent-free electrolyte exhibited a good long-term stability without a drop of the current density.

Thin Solid Films, 2006

The nature and morphology of titanium dioxide films play a significant role in determining the ov... more The nature and morphology of titanium dioxide films play a significant role in determining the overall efficiency of the dye sensitised solar cell (DSSC). The influence of three different nanocrystalline titania films, prepared from three different routes, namely sol–gel (FMF), thermal (P-25), and colloidal-microwave process (CMP), on the performance of solid-state dye sensitised solar cells was studied and discussed here. The difference in the preparation of nanotitania leads to different surface area, pore size and morphology of the mesoporous films. FMF–TiO2 displayed the highest efficiency and IPCE in DSSC among the other two because it possessed pure anatase phase, optimum surface area, pore volume and pore diameter; and well-connected network of individual nanoparticles. P-25 films exhibited pore structural and morphological features similar to FMF films but it displayed lower efficiency than FMF–TiO2 due to the presence of small percentage of rutile phase besides major anatase phase. Although, CMP films had high surface area, it possessed smaller pore diameter and pore volume besides agglomerates and macropores leading to lower efficiency. The work clearly demonstrates the optimal pore and morphological structures required for efficient functioning of solid-state dye sensitised solar cell.

Thin Solid Films, 2008

A small organic sensitizer, the polyene-diphenylaniline dye D5, was compared with the standard se... more A small organic sensitizer, the polyene-diphenylaniline dye D5, was compared with the standard sensitizer N719 (Ru (dcbpy) 2 (NCS) 2) in a dye-sensitized solar cell investigation. In solar cells with relatively thin layers of mesoporous TiO2 (< 3 μm) D5 outperformed ...

Polymers for Advanced Technologies, 2007

Polymer composite foams or syntactic foams containing 0.9, 1.76, 2.54, 3.54 and 4.5 vol% of E‐gla... more Polymer composite foams or syntactic foams containing 0.9, 1.76, 2.54, 3.54 and 4.5 vol% of E‐glass short fibers were processed and subjected to a three‐point bending test. The results show that the flexural modulus increased with fiber content, with the exception of 1.76% and 3.5% of fibers. This deviation was due to a higher void content for 1.76% and a non‐uniform distribution of fibers in the polymer composite foam system for 3.5%. However, in general, the incorporation of chopped strand fibers improved the flexural behavior of the syntactic foam system without much variation in density, thus making the reinforced syntactic foams act as improved core materials for sandwich and other structural applications. Copyright © 2007 John Wiley & Sons, Ltd.

Materialwissenschaft und Werkstofftechnik, 2006

ABSTRACT Zur Herstellung von nanopartikulären keramischen Pulvern verschiedener Oxide, wie TiO2 u... more ABSTRACT Zur Herstellung von nanopartikulären keramischen Pulvern verschiedener Oxide, wie TiO2 und Gd2O3, wurde eine veränderte mikrowellenunterstützte Polyolmethode (MAP) verwendet. Aufgrund der guten dielektrischen Eigenschaften der verwendeten Lösungsmittel, wie Diethylenglykol und 1,4 Butandiol, ist Mikrowellenheizen möglich, wodurch eine bedeutende Reduzierung der Reaktionszeit erhalten wird. Die Pulver haben eine mittlere Primärpartikelgröße von &lt; 5 nm. Einflüsse auf die Partikelgröße und -verteilung sowie die Porengrößenverteilung und Oberflächengröße wurden durch Variation des Prekursors, dessen Konzentration im Lösungsmittel, der zugegebenen Menge an Wasser oder Hydroxid, des pH-Werts der Lösung und der MW-Parameter untersucht. Pulver, die über diese Route hergestellt wurden, zeigen die Eigenschaft, Polyol in die molekulare Struktur zu interkalieren. Diese Besonderheit, über die auch eine japanische Gruppe berichtet, wird ebenso beleuchtet und dürfte neue technische Anwendungsfelder eröffnen. Die allgemeine Anwendbarkeit dieser Methode und deren Vorteile bezüglich Eigenschaften der Pulver und Verarbeitbarkeit werden gezeigt. Die Pulver wurden mittels Röntgenbeugung, Elektronenmikroskopie und Physisorption untersucht.

Macromolecular Materials and Engineering, 2003

A novel nanocomposite based on Nafion® (ionomer) and a layered silicate is studied. An innovative... more A novel nanocomposite based on Nafion® (ionomer) and a layered silicate is studied. An innovative approach of processing a composite under electric field to induce orientation of the inorganic filler was carried out and accomplished in the present work. The morphology of oriented composites was analyzed by scanning electric potential microscopy (SEPM) and transmission electron microscopy (TEM). Films based on both plain ionomer and composite displayed fine contrast in SEPM, differentiating the phases, which could not be achieved using conventional atomic force microscopy. The orientation of the silicates in the composites is evident from the SEPM picture.AFM of Nafion®/montmorillonite composite films prepared by solution casting under electric field (Image obtained by SEPM).magnified imageAFM of Nafion®/montmorillonite composite films prepared by solution casting under electric field (Image obtained by SEPM).

Journal of Non-Crystalline Solids, 2005

... It is comprised of negatively charged silica sheets held together by charge-balancing counter... more ... It is comprised of negatively charged silica sheets held together by charge-balancing counterions such as Mg 2+ , Na + , and Ca 2+ . The general chemical formula of the montmorillonite is (M + ×nH 2 O)(Al (4−y) Mg y )Si 8 O 20 (OH) 4 , where M (M = Na + , Ca 2+ , Mg 2+ , etc ...

Journal of Membrane Science, 2005

Polymer nanocomposite membranes based on sulphonated poly(ether ether ketone) (SPEEK) containing ... more Polymer nanocomposite membranes based on sulphonated poly(ether ether ketone) (SPEEK) containing different weight percentages of synthetic non-spherical nanofillers such as laponite and MCM-41 were prepared and characterised for direct methanol fuel cells (DMFC). Prior to the preparation of the composite membranes, they were modified using organo silanes. The results showed that there was a decrease in methanol and water permeability

European Polymer Journal, 2005

Polymer composite membranes based on sulphonated polymers, such as sulphonated poly(ether ketone)... more Polymer composite membranes based on sulphonated polymers, such as sulphonated poly(ether ketone) and sulphonated poly(ether ether ketone), and silicates were prepared and characterized for water/methanol permeabilities and proton conductivity studies. The study showed methanol and water permeability in the composite system decreased, with respect to the plain polymer/ionomer, with the increase in content of silicates. The permeability reduction in the composite membranes is discussed using models and theories. It was also found that the proton conductivity of the ionomer-composite membranes increased with the increase in total flux of the system, emphasising a good correlation between the total flux of the composite membranes and proton conductivity. The work clearly demonstrates that the same transport mechanism governs both methanol-water crossover and proton conductivity in these polymer electrolyte composite membranes.

The Journal of Physical Chemistry C, 2008

We present a photophysical and device-based investigation of a new bipyridyl-NCS ruthenium comple... more We present a photophysical and device-based investigation of a new bipyridyl-NCS ruthenium complex sensitizer with an extended π system, in both sensitized TiO 2 and incorporated into solid-state dye-sensitized solar cells. We compare this new sensitizer to an analog dye without the extended π system. We observe very similar excited-state absorption spectra and charge recombination kinetics for the two systems. However, the π-extended senstizer has a phenomenally enhanced molar extinction coefficient which translates into far greater light harvesting and current collection in solid-state dye-sensitized solar cells. We also infer from transient photovoltage measurements that positioning the pendent extended π system away from the TiO 2 surface has induced a favorable dipole shift, generating enhanced open-circuit voltage. The resulting power conversion efficiency for the solar cell has been increased from 2.4% to 3.2% when comparing the new sensitizer to an analogy with no pendent group.

Macromolecular Chemistry and Physics, 2006

Inorganica Chimica Acta, 2008

In this feature article, we discuss the key aspects of solid-state dye-sensitized solar cells (SD... more In this feature article, we discuss the key aspects of solid-state dye-sensitized solar cells (SDSC) and propose different concepts based on extensive studies carried out in our group to improve their performance. The influence of compact TiO 2 layer, novel donor-antenna sensitizing dyes, nature of nanocrystalline-TiO 2 layers and solid-state organic hole conductors on the performance of SDSC is discussed in this article. Both preparation and thickness of the compact TiO 2 layer were optimized using spray pyrolysis. The studies revealed that an optimum film thickness of 120-150 nm of compact TiO 2 yielded the best rectifying behavior and SDSC performance. The influence of three different mesoporous titania films, obtained from three different titania nanocrystals, prepared by sol-gel, thermal, and colloidalmicrowave process, was also studied and discussed here. The TiO 2 layer with the optimum pore volume and pore diameter ($44 nm) displayed the highest efficiency and IPCE in SDSC. The importance of pore size rather than high surface area for filling the mesoporous layer with solid-state hole conductor became evident from this study. A series of heteroleptic Ru(II) complexes carrying donor antenna moieties, namely, triphenylamine (TPA) or N,N 0 -bis(phenyl)-N,N 0 -bis(3-methylphenyl)-1,1 0 -biphenyl-4,4 0 -diamine (TPD), were synthesized and applied in SDSC. These novel donor-antenna dyes revealed spectacular performances of power conversion efficiencies in the range 1.5-3.4%, as measured under AM 1.5 spectral conditions. This was attributed to highly efficient light harvesting of these novel dyes and the improved charge-transfer dynamics at TiO 2 -dye and dye-hole conductor interfaces. Different low molecular weight and polymeric triphenyldiamines were synthesized and utilized as hole-transporting layers (HTL) in SDSC. Different studies showed that low molecular TPDs displayed better efficiency than polymeric counterparts due to their improved filling into the pores of nc-TiO 2 layer. Another interesting study revealed that an optimum driving force in terms of HOMO-level difference between the dye and HTL decides charge carrier generation efficiency. Recently, novel hole conductors with spiro-bifluorene-triphenylamine core for transporting holes and tetraethylene glycol side chains for binding lithium ions were synthesized and applied in SDSC. This work clearly emphasizes that Li + -salt is required at the TiO 2 /dye interface as well as in the bulk of HTL. It was also found that the addition of about 5-20% of these Li + -binding hole conductors and higher Li-salt (N-lithiotrifluoromethane sulfonamide) concentrations improved the SDSC performance. An improvement of about 120% in the solar cell efficiency as compared to the reference cells was achieved with an optimum composition of Li + -binding hole conductor and Li-salt.

Advanced Engineering Materials, 2006

Page 1. – [1] K. Weinert, M. Hagedorn, C. Peters, Techn. 2004, 22, 16. [2] K. Weinert, C. Kempman... more Page 1. – [1] K. Weinert, M. Hagedorn, C. Peters, Techn. 2004, 22, 16. [2] K. Weinert, C. Kempmann, Adv. Eng. Mater. 2004, 8, 684. [3] F. Klocke, M. Rehse, Production Eng. 1997, IV/2, 65. [4] M. Schneeweiß, VDI-Z Spec. Werkzeuge ...

A new heteroleptic ruthenium(II) complex cis-di(thiocyanato)(4,4 0 -dicarboxylic acid-2,2 0bipyri... more A new heteroleptic ruthenium(II) complex cis-di(thiocyanato)(4,4 0 -dicarboxylic acid-2,2 0bipyridine)(4,4 0 -bis[(triethylene glycol methyl ether)(ditolylamine phenyl)ethenyl]-2,2 0 -bipyridine) ruthenium(II) (Ru-TPA-EO-NCS) was synthesized and characterized as a sensitizer for dye-sensitized solar cell application. The ligand contributes to enhance the light harvesting yield rendering a high short-circuit current density of 18.3 mA/cm 2 at full sun condition (1000 W/m 2 ) leading to an efficient dye-sensitized solar cell. The dye is explored for solid-state solar cell based on 2.0 mm thick thin TiO 2 film with organic hole transport material, Spiro-MeOTAD and it turns out to render 3.3% at full sun. The stability of DSCs is an important aspect for their commercialization. In this respect, the dye in conjunction with a solvent-free electrolyte exhibited a good long-term stability without a drop of the current density.

Laine/Ceramic, 2012

The nature and micro-structure of titania plays an important role in determining the overall effi... more The nature and micro-structure of titania plays an important role in determining the overall efficiency of the solar cell. The influence of three different nanocrystalline titania, prepared from three different routes, namely sol-gel, thermal, and colloidal-microwave process, on the performance of solid state dye sensitized solar cells was studied and reported here. The difference in the preparation of nanomaterials leads to different surface area, pore size and morphology of the mesoporous films. A methodical investigation on how such films with different structure and morphology affect the performance of solid-state dye sensitized solar cell is reported and discussed in this article. To support an investigation of this nature, XRD, BET, and scanning electron microscopy (SEM) were utilzed to have a clear understanding of the actual structure and morphology of mesoporous titania films applied in solid state DSSC. The work clearly demonstrates the optimal pore and morphological structures required for efficient functioning of solid-state dye sensitized solar cell.

Nano Energy, 2012

A new heteroleptic ruthenium(II) complex cis-di(thiocyanato)(4,4 0-dicarboxylic acid-2,2 0bipyrid... more A new heteroleptic ruthenium(II) complex cis-di(thiocyanato)(4,4 0-dicarboxylic acid-2,2 0bipyridine)(4,4 0-bis[(triethylene glycol methyl ether)(ditolylamine phenyl)ethenyl]-2,2 0-bipyridine) ruthenium(II) (Ru-TPA-EO-NCS) was synthesized and characterized as a sensitizer for dyesensitized solar cell application. The ligand contributes to enhance the light harvesting yield rendering a high short-circuit current density of 18.3 mA/cm 2 at full sun condition (1000 W/m 2) leading to an efficient dye-sensitized solar cell. The dye is explored for solid-state solar cell based on 2.0 mm thick thin TiO 2 film with organic hole transport material, Spiro-MeOTAD and it turns out to render 3.3% at full sun. The stability of DSCs is an important aspect for their commercialization. In this respect, the dye in conjunction with a solvent-free electrolyte exhibited a good long-term stability without a drop of the current density.

Thin Solid Films, 2006

The nature and morphology of titanium dioxide films play a significant role in determining the ov... more The nature and morphology of titanium dioxide films play a significant role in determining the overall efficiency of the dye sensitised solar cell (DSSC). The influence of three different nanocrystalline titania films, prepared from three different routes, namely sol–gel (FMF), thermal (P-25), and colloidal-microwave process (CMP), on the performance of solid-state dye sensitised solar cells was studied and discussed here. The difference in the preparation of nanotitania leads to different surface area, pore size and morphology of the mesoporous films. FMF–TiO2 displayed the highest efficiency and IPCE in DSSC among the other two because it possessed pure anatase phase, optimum surface area, pore volume and pore diameter; and well-connected network of individual nanoparticles. P-25 films exhibited pore structural and morphological features similar to FMF films but it displayed lower efficiency than FMF–TiO2 due to the presence of small percentage of rutile phase besides major anatase phase. Although, CMP films had high surface area, it possessed smaller pore diameter and pore volume besides agglomerates and macropores leading to lower efficiency. The work clearly demonstrates the optimal pore and morphological structures required for efficient functioning of solid-state dye sensitised solar cell.

Thin Solid Films, 2008

A small organic sensitizer, the polyene-diphenylaniline dye D5, was compared with the standard se... more A small organic sensitizer, the polyene-diphenylaniline dye D5, was compared with the standard sensitizer N719 (Ru (dcbpy) 2 (NCS) 2) in a dye-sensitized solar cell investigation. In solar cells with relatively thin layers of mesoporous TiO2 (< 3 μm) D5 outperformed ...

Polymers for Advanced Technologies, 2007

Polymer composite foams or syntactic foams containing 0.9, 1.76, 2.54, 3.54 and 4.5 vol% of E‐gla... more Polymer composite foams or syntactic foams containing 0.9, 1.76, 2.54, 3.54 and 4.5 vol% of E‐glass short fibers were processed and subjected to a three‐point bending test. The results show that the flexural modulus increased with fiber content, with the exception of 1.76% and 3.5% of fibers. This deviation was due to a higher void content for 1.76% and a non‐uniform distribution of fibers in the polymer composite foam system for 3.5%. However, in general, the incorporation of chopped strand fibers improved the flexural behavior of the syntactic foam system without much variation in density, thus making the reinforced syntactic foams act as improved core materials for sandwich and other structural applications. Copyright © 2007 John Wiley & Sons, Ltd.

Materialwissenschaft und Werkstofftechnik, 2006

ABSTRACT Zur Herstellung von nanopartikulären keramischen Pulvern verschiedener Oxide, wie TiO2 u... more ABSTRACT Zur Herstellung von nanopartikulären keramischen Pulvern verschiedener Oxide, wie TiO2 und Gd2O3, wurde eine veränderte mikrowellenunterstützte Polyolmethode (MAP) verwendet. Aufgrund der guten dielektrischen Eigenschaften der verwendeten Lösungsmittel, wie Diethylenglykol und 1,4 Butandiol, ist Mikrowellenheizen möglich, wodurch eine bedeutende Reduzierung der Reaktionszeit erhalten wird. Die Pulver haben eine mittlere Primärpartikelgröße von &lt; 5 nm. Einflüsse auf die Partikelgröße und -verteilung sowie die Porengrößenverteilung und Oberflächengröße wurden durch Variation des Prekursors, dessen Konzentration im Lösungsmittel, der zugegebenen Menge an Wasser oder Hydroxid, des pH-Werts der Lösung und der MW-Parameter untersucht. Pulver, die über diese Route hergestellt wurden, zeigen die Eigenschaft, Polyol in die molekulare Struktur zu interkalieren. Diese Besonderheit, über die auch eine japanische Gruppe berichtet, wird ebenso beleuchtet und dürfte neue technische Anwendungsfelder eröffnen. Die allgemeine Anwendbarkeit dieser Methode und deren Vorteile bezüglich Eigenschaften der Pulver und Verarbeitbarkeit werden gezeigt. Die Pulver wurden mittels Röntgenbeugung, Elektronenmikroskopie und Physisorption untersucht.

Macromolecular Materials and Engineering, 2003

A novel nanocomposite based on Nafion® (ionomer) and a layered silicate is studied. An innovative... more A novel nanocomposite based on Nafion® (ionomer) and a layered silicate is studied. An innovative approach of processing a composite under electric field to induce orientation of the inorganic filler was carried out and accomplished in the present work. The morphology of oriented composites was analyzed by scanning electric potential microscopy (SEPM) and transmission electron microscopy (TEM). Films based on both plain ionomer and composite displayed fine contrast in SEPM, differentiating the phases, which could not be achieved using conventional atomic force microscopy. The orientation of the silicates in the composites is evident from the SEPM picture.AFM of Nafion®/montmorillonite composite films prepared by solution casting under electric field (Image obtained by SEPM).magnified imageAFM of Nafion®/montmorillonite composite films prepared by solution casting under electric field (Image obtained by SEPM).

Journal of Non-Crystalline Solids, 2005

... It is comprised of negatively charged silica sheets held together by charge-balancing counter... more ... It is comprised of negatively charged silica sheets held together by charge-balancing counterions such as Mg 2+ , Na + , and Ca 2+ . The general chemical formula of the montmorillonite is (M + ×nH 2 O)(Al (4−y) Mg y )Si 8 O 20 (OH) 4 , where M (M = Na + , Ca 2+ , Mg 2+ , etc ...

Journal of Membrane Science, 2005

Polymer nanocomposite membranes based on sulphonated poly(ether ether ketone) (SPEEK) containing ... more Polymer nanocomposite membranes based on sulphonated poly(ether ether ketone) (SPEEK) containing different weight percentages of synthetic non-spherical nanofillers such as laponite and MCM-41 were prepared and characterised for direct methanol fuel cells (DMFC). Prior to the preparation of the composite membranes, they were modified using organo silanes. The results showed that there was a decrease in methanol and water permeability

European Polymer Journal, 2005

Polymer composite membranes based on sulphonated polymers, such as sulphonated poly(ether ketone)... more Polymer composite membranes based on sulphonated polymers, such as sulphonated poly(ether ketone) and sulphonated poly(ether ether ketone), and silicates were prepared and characterized for water/methanol permeabilities and proton conductivity studies. The study showed methanol and water permeability in the composite system decreased, with respect to the plain polymer/ionomer, with the increase in content of silicates. The permeability reduction in the composite membranes is discussed using models and theories. It was also found that the proton conductivity of the ionomer-composite membranes increased with the increase in total flux of the system, emphasising a good correlation between the total flux of the composite membranes and proton conductivity. The work clearly demonstrates that the same transport mechanism governs both methanol-water crossover and proton conductivity in these polymer electrolyte composite membranes.

The Journal of Physical Chemistry C, 2008

We present a photophysical and device-based investigation of a new bipyridyl-NCS ruthenium comple... more We present a photophysical and device-based investigation of a new bipyridyl-NCS ruthenium complex sensitizer with an extended π system, in both sensitized TiO 2 and incorporated into solid-state dye-sensitized solar cells. We compare this new sensitizer to an analog dye without the extended π system. We observe very similar excited-state absorption spectra and charge recombination kinetics for the two systems. However, the π-extended senstizer has a phenomenally enhanced molar extinction coefficient which translates into far greater light harvesting and current collection in solid-state dye-sensitized solar cells. We also infer from transient photovoltage measurements that positioning the pendent extended π system away from the TiO 2 surface has induced a favorable dipole shift, generating enhanced open-circuit voltage. The resulting power conversion efficiency for the solar cell has been increased from 2.4% to 3.2% when comparing the new sensitizer to an analogy with no pendent group.

Macromolecular Chemistry and Physics, 2006

Inorganica Chimica Acta, 2008

In this feature article, we discuss the key aspects of solid-state dye-sensitized solar cells (SD... more In this feature article, we discuss the key aspects of solid-state dye-sensitized solar cells (SDSC) and propose different concepts based on extensive studies carried out in our group to improve their performance. The influence of compact TiO 2 layer, novel donor-antenna sensitizing dyes, nature of nanocrystalline-TiO 2 layers and solid-state organic hole conductors on the performance of SDSC is discussed in this article. Both preparation and thickness of the compact TiO 2 layer were optimized using spray pyrolysis. The studies revealed that an optimum film thickness of 120-150 nm of compact TiO 2 yielded the best rectifying behavior and SDSC performance. The influence of three different mesoporous titania films, obtained from three different titania nanocrystals, prepared by sol-gel, thermal, and colloidalmicrowave process, was also studied and discussed here. The TiO 2 layer with the optimum pore volume and pore diameter ($44 nm) displayed the highest efficiency and IPCE in SDSC. The importance of pore size rather than high surface area for filling the mesoporous layer with solid-state hole conductor became evident from this study. A series of heteroleptic Ru(II) complexes carrying donor antenna moieties, namely, triphenylamine (TPA) or N,N 0 -bis(phenyl)-N,N 0 -bis(3-methylphenyl)-1,1 0 -biphenyl-4,4 0 -diamine (TPD), were synthesized and applied in SDSC. These novel donor-antenna dyes revealed spectacular performances of power conversion efficiencies in the range 1.5-3.4%, as measured under AM 1.5 spectral conditions. This was attributed to highly efficient light harvesting of these novel dyes and the improved charge-transfer dynamics at TiO 2 -dye and dye-hole conductor interfaces. Different low molecular weight and polymeric triphenyldiamines were synthesized and utilized as hole-transporting layers (HTL) in SDSC. Different studies showed that low molecular TPDs displayed better efficiency than polymeric counterparts due to their improved filling into the pores of nc-TiO 2 layer. Another interesting study revealed that an optimum driving force in terms of HOMO-level difference between the dye and HTL decides charge carrier generation efficiency. Recently, novel hole conductors with spiro-bifluorene-triphenylamine core for transporting holes and tetraethylene glycol side chains for binding lithium ions were synthesized and applied in SDSC. This work clearly emphasizes that Li + -salt is required at the TiO 2 /dye interface as well as in the bulk of HTL. It was also found that the addition of about 5-20% of these Li + -binding hole conductors and higher Li-salt (N-lithiotrifluoromethane sulfonamide) concentrations improved the SDSC performance. An improvement of about 120% in the solar cell efficiency as compared to the reference cells was achieved with an optimum composition of Li + -binding hole conductor and Li-salt.

Advanced Engineering Materials, 2006

Page 1. – [1] K. Weinert, M. Hagedorn, C. Peters, Techn. 2004, 22, 16. [2] K. Weinert, C. Kempman... more Page 1. – [1] K. Weinert, M. Hagedorn, C. Peters, Techn. 2004, 22, 16. [2] K. Weinert, C. Kempmann, Adv. Eng. Mater. 2004, 8, 684. [3] F. Klocke, M. Rehse, Production Eng. 1997, IV/2, 65. [4] M. Schneeweiß, VDI-Z Spec. Werkzeuge ...

A new heteroleptic ruthenium(II) complex cis-di(thiocyanato)(4,4 0 -dicarboxylic acid-2,2 0bipyri... more A new heteroleptic ruthenium(II) complex cis-di(thiocyanato)(4,4 0 -dicarboxylic acid-2,2 0bipyridine)(4,4 0 -bis[(triethylene glycol methyl ether)(ditolylamine phenyl)ethenyl]-2,2 0 -bipyridine) ruthenium(II) (Ru-TPA-EO-NCS) was synthesized and characterized as a sensitizer for dye-sensitized solar cell application. The ligand contributes to enhance the light harvesting yield rendering a high short-circuit current density of 18.3 mA/cm 2 at full sun condition (1000 W/m 2 ) leading to an efficient dye-sensitized solar cell. The dye is explored for solid-state solar cell based on 2.0 mm thick thin TiO 2 film with organic hole transport material, Spiro-MeOTAD and it turns out to render 3.3% at full sun. The stability of DSCs is an important aspect for their commercialization. In this respect, the dye in conjunction with a solvent-free electrolyte exhibited a good long-term stability without a drop of the current density.