Showing papers by "Michael Grätzel published in 2009"
TL;DR: The discussion focuses on mesoscopic solar cells, in particular, dye-sensitized solar cells (DSCs), which have been developed in the laboratory and remain the focus of the investigations, and aims at identifying and providing solutions to the efficiency problems that the OPV field is still facing.
Abstract: Perhaps the largest challenge for our global society is to find ways to replace the slowly but inevitably vanishing fossil fuel supplies by renewable resources and, at the same time, avoid negative effects from the current energy system on climate, environment, and health. The quality of human life to a large degree depends upon the availability of clean energy sources. The worldwide power consumption is expected to double in the next 3 decades because of the increase in world population and the rising demand of energy in the developing countries. This implies enhanced depletion of fossil fuel reserves, leading to further aggravation of the environmental pollution. As a consequence of dwindling resources, a huge power supply gap of 14 terawatts is expected to open up by year 2050 equaling today’s entire consumption, thus threatening to create a planetary emergency of gigantic dimensions. Solar energy is expected to play a crucial role as a future energy source. The sun provides about 120 000 terawatts to ...
2,490 citations
TL;DR: A high molar extinction coefficient heteroleptic ruthenium complex, incorporating an electron-rich hexylthio-terminal chain, has been synthesized and demonstrated as an efficient sensitizer for dye-sensitized solar cells.
Abstract: A high molar extinction coefficient heteroleptic ruthenium complex, incorporating an electron-rich hexylthio-terminal chain, has been synthesized and demonstrated as an efficient sensitizer for dye...
1,178 citations
TL;DR: An efficient nonplatinized flexible counter electrode for dye-sensitized solar cells using an amphiphilic ruthenium polypyridyl photosensitizer with higher electrocatalytic activity for the reduction of triiodide is reported.
Abstract: We report an efficient nonplatinized flexible counter electrode for dye-sensitized solar cells. In combination with a solvent-free ionic liquid electrolyte, we have demonstrated a ∼6.5% cell with an amphiphilic ruthenium polypyridyl photosensitizer showing excellent stability measured under prolonged light soaking at 60 °C. Compared to the Pt deposited PEN film, the CoS deposited PEN film shows higher electrocatalytic activity for the reduction of triiodide. This is expected to have an important practical consequence on the production of flexible low-cost and lightweight thin film DSC devices based on the plastic matrix.
855 citations
TL;DR: Light-harvesting properties and transient voltage decay/impedance measurements confirmed that CdTe-terminated CdSe QD cells gave better charge-collection efficiencies and kinetic parameters than corresponding Cd selenideQD cells.
Abstract: In pursuit of efficient quantum dot (QD)-sensitized solar cells based on mesoporous TiO2 photoanodes, a new procedure for preparing selenide (Se2−) was developed and used for depositing CdSe QDs in situ over TiO2 mesopores by the successive ionic layer adsorption and reaction (SILAR) process in ethanol. The sizes and density of CdSe QDs over TiO2 were controlled by the number of SILAR cycles applied. After some optimization of these QD-sensitized TiO2 films in regenerative photoelectrochemical cells using a cobalt redox couple [Co(o-phen)32+/3+], including addition of a final layer of CdTe, over 4% overall efficiencies were achieved at 100 W/m2 with about 50% IPCE at its maximum. Light-harvesting properties and transient voltage decay/impedance measurements confirmed that CdTe-terminated CdSe QD cells gave better charge-collection efficiencies and kinetic parameters than corresponding CdSe QD cells. In a preliminary study, a CdSe(Te) QD-sensitized TiO2 film was combined with an organic hole conductor, spi...
622 citations
TL;DR: In this article, Raman and Mossbauer showed that photoanodes consisting of nanostructured hematite prepared by atmospheric pressure chemical vapor deposition (APCVD) have previously set a benchmark for solar water splitting.
Abstract: Photoanodes consisting of nanostructured hematite prepared by atmospheric pressure chemical vapor deposition (APCVD) have previously set a benchmark for solar water splitting. Here, we fully investigate this promising system by varying critical synthetic parameters and probing the photoanode performance to determine the major factors that influence operation. By varying the film thickness, we show film growth to be linear with an incubation time. We find no concern with electron transport for films up to 600 nm, but a higher recombination rate of photogenerated carriers in the hematite near the interface with the fluorine-doped tin oxide, as compared to the bulk section of the film. The mechanism for the formation of the thin film’s nanoporous dendritic structure is discussed on the basis of the results from varying the substrate growth temperate. The observed feature sizes of the film are found to depend strongly on this temperature and the presence of silicon dopant precursor (TEOS). Raman and Mossbauer...
604 citations
TL;DR: In this article, the performance of lead sulfide and cadmium sulfide (CdS) quantum dots (QDs) was investigated in solid-state solar cells with 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spiro-OMeTAD+ cation.
Abstract: Lead sulfide (PbS) and cadmium sulfide (CdS) quantum dots (QDs) are prepared over mesoporous TiO2 films by a successive ionic layer adsorption and reaction (SILAR) process. These QDs are exploited as a sensitizer in solid-state solar cells with 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) as a hole conductor. High-resolution transmission electron microscopy (TEM) images reveal that PbS QDs of around 3 nm in size are distributed homogeneously over the TiO2 surface and are well separated from each other if prepared under common SILAR deposition conditions. The pore size of the TiO2 films and the deposition medium are found to be very critical in determining the overall performance of the solid-state QD cells. By incorporating promising inorganic QDs (PbS) and an organic hole conductor spiro-OMeTAD into the solid-state cells, it is possible to attain an efficiency of over 1% for PbS-sensitized solid-state cells after some optimizations. The optimized deposition cycle of the SILAR process for PbS QDs has also been confirmed by transient spectroscopic studies on the hole generation of spiro-OMeTAD. In addition, it is established that the PbS QD layer plays a role in mediating the interfacial recombination between the spiro-OMeTAD+ cation and the TiO2 conduction band electron, and that the lifetime of these species can change by around 2 orders of magnitude by varying the number of SILAR cycles used. When a near infrared (NIR)-absorbing zinc carboxyphthalocyanine dye (TT1) is added on top of the PbS-sensitized electrode to obtain a panchromatic response, two signals from each component are observed, which results in an improved efficiency. In particular, when a CdS-sensitized electrode is first prepared, and then co-sensitized with a squarine dye (SQ1), the resulting color change is clearly an addition of each component and the overall efficiencies are also added in a more synergistic way than those in PbS/TT1-modified cells because of favorable charge-transfer energetics.
469 citations
TL;DR: In this article, a nanostructured host scaffold (WO3) prepared by atmospheric pressure CVD was used to support a thin layer of Fe2O3 nanoparticles deposited by a similar method.
Abstract: Solar hydrogen production via watersplitting with hematite (Fe2O3) has been limited by poor light absorption and a small hole diffusion length. These drawbacks can be overcome by using a high-surface-area host to support a thin layer of hematite—allowing photogenerated holes to be produced in high proximity to the semiconductor-liquid junction. Here we demonstrate the effectiveness of this concept using a nanostructured host scaffold (WO3) prepared by atmospheric pressure CVD to support a thin layer of Fe2O3 nanoparticles deposited by a similar method. A 20% increase in the photocurrent was observed in host−guest electrodes as compared to control films with the same amount of hematite (equivalent to a 60 nm film) deposited without the host scaffold. The improvement is attributed to an increase in the absorbed photon conversion efficiency (APCE), especially for longer wavelengths where the photon penetration depth is large in hematite. For light with a wavelength of 565 nm, the APCE improves to 8.0%, as co...
451 citations
TL;DR: In this paper, a new dye-sensitized solar cell architecture was proposed where high-energy photons are absorbed by highly photoluminescent chromophores unattached to the titania and undergo Forster resonant energy transfer to the sensitizing dye.
Abstract: Conventional dye-sensitized solar cells have excellent charge collection efficiencies, high open-circuit voltages and good fill factors. However, dye-sensitized solar cells do not completely absorb all of the photons from the visible and near-infrared domain and consequently have lower short-circuit photocurrent densities than inorganic photovoltaic devices. Here, we present a new design where high-energy photons are absorbed by highly photoluminescent chromophores unattached to the titania and undergo Forster resonant energy transfer to the sensitizing dye. This novel architecture allows for broader spectral absorption, an increase in dye loading, and relaxes the design requirements for the sensitizing dye. We demonstrate a 26% increase in power conversion efficiency when using an energy relay dye (PTCDI) with an organic sensitizing dye (TT1). We estimate the average excitation transfer efficiency in this system to be at least 47%. This system offers a viable pathway to develop more efficient dye-sensitized solar cells.
450 citations
TL;DR: It is shown that electron transport mechanisms in TiO(2) solid-state dye-sensitized solar cells (SDSCs) with spiro-OMeTAD as hole conductor are similar to those of high-performance DSCs with liquid electrolytes and ionic liquids.
Abstract: We show that electron transport mechanisms in TiO2 solid-state dye-sensitized solar cells (SDSCs) with spiro-OMeTAD as hole conductor are similar to those of high-performance DSCs with liquid electrolytes and ionic liquids. Impedance spectroscopy provides the parameters for transport and recombination at different conditions of steady state in the dark. The recombination rate is much higher in the solid solar cell, this being a main limiting step to obtain high-efficiency SDSCs. Thus, the expected gain in photovoltage, due to a lower hole Fermi level, is prevented by recombination losses. Under low potentials the transport is limited by the electron transport in the TiO2, but at high potentials spiro-OMeTAD transport resistance reduces the fill factor and hence the efficiency on high-current devices.
423 citations
TL;DR: In this paper, the contribution of a Grotthous-type exchange mechanism in these viscous electrolytes helps to alleviate the diffusion problems in dye-sensitized solar cells.
Abstract: Ionic liquids have been identified as a new class of solvent that offers opportunities to move away from the traditional solvents. The physical-chemical properties of ionic liquids can be tuned and controlled by tailoring their structures. The typical properties of ionic liquids, such as non-volatility, electrochemical stability and high conductivity, render them attractive as electrolytes for dye-sensitized solar cells. However, the high viscosity of ionic liquids leads to mass transport limitations on the photocurrents in the solar cells at full sunlight intensity, but the contribution of a Grotthous-type exchange mechanism in these viscous electrolytes helps to alleviate these diffusion problems. This article discusses recent developments in the field of high-performance dye-sensitized solar cells with ionic liquid-based electrolytes and their characterization by electrochemical impedance analysis.
423 citations
TL;DR: The present findings provide new design criteria for the next generation of ruthenium sensitizers and help foster widespread interest in the engineering of new sensitizer that interact effectively with the I(-)/I(3)(-) redox couple.
Abstract: A novel thiocyanate-free cyclometalleted ruthenium sensitizer for solar cells is designed and developed. Upon anchoring to nanocrystalline TiO2 films, it exhibits a remarkable incident monochromatic photon-to-current conversion efficiency of 83%. The solar cell employing a liquid-based electrolyte exhibits a short circuit photocurrent density of 17 mA/cm(2), an open circuit voltage of 800 mV, and a fill factor of 0.74, corresponding to an overall conversion efficiency of 10.1% at standard AM 1.5 sunlight. To understand the structural, electronic, and optical properties of the cyclometalleted ruthenium sensitizer, we have investigated using density functional theory (DFT) and time-dependent DFT (TDDFT). Our results show the HOMO is located mostly on ruthenium and cyclometalated ligand, while the LUMO is on 4-carboxylic acid-4'-carboxylate-2,2'-bipyridine. Molecular orbitals analysis confirmed the experimental assignment of redox potentials, and TDDFT calculations allowed assignment of the visible absorption bands. The present findings provide new design criteria for the next generation of ruthenium sensitizers and help foster widespread interest in the engineering of new sensitizers that interact effectively with the I-/I-3(-) redox couple.
TL;DR: In this paper, the currentvoltage characteristics of single nanowires were measured in the dark and under various illumination conditions including 1.5 AM, and the total efficiency was 4.5%.
Abstract: Gallium arsenide p-i-n radial junctions were fabricated by molecular beam epitaxy. The current-voltage characteristics of single nanowires were measured in the dark and under various illumination conditions including 1.5 AM. The total efficiency was 4.5%. Spatially resolved and power dependent photocurrent measurements indicate that the p-i-n junction is homogeneous along the nanowire. Electroluminescence measurements show an emission peak at about 1.4 eV, further corroborating the good quality of the nanowire. These results constitute an important progress for the use of nanowires in photovoltaic applications.
TL;DR: In this paper, a novel polyol synthesis was adopted to synthesize nano-structured LiMnPO4 and the obtained material presented a good rate behavior and a very long cyclic life both at room temperature (RT) and at elevated temperature (50 degrees C) this material demonstrated improved reversible capacity of 159 mAh g(-1) at C/10 and 138 at 1C.
TL;DR: In this paper, the pore filling of spiro-OMeTAD (2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)9,9'-spirobifluorene) in mesoporous TiO2 film is quantified for the first time using XPS depth profiling and UV-Vis absorption spectroscopy.
Abstract: In this paper, the pore filling of spiro-OMeTAD (2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)9,9'-spirobifluorene) in mesoporous TiO2 film is quantified for the first time using XPS depth profiling and UV-Vis absorption spectroscopy. It is shown that spiro-OMeTAD can penetrate the entire depth of the film, and its concentration is constant throughout the film. We determine that in a 2.5-mu m-thick film, the volume of the pores is 60-65% filled. The pores become less filled when thicker films are used. Such filling fraction is much higher then the solution concentration because the excess solution on top of the film can act as a reservior during the spin coating process. Lastly, we demonstrate that by using a lower spin coating speed and higher spiro-OMeTAD solution concentration, we can increase the filling fraction and consequently the efficiency of the device.
TL;DR: The cobalt complex herein used as a regenerative redox couple was found to be more efficient in generating photocurrents from PbS QD cells than the typical hole scavenger Na2S in a three-electrode configuration.
Abstract: Metal sulfide (PbS and CdS) quantum dots (QDs) were prepared over mesoporous TiO2 films by improved successive ionic layer adsorption and reaction (SILAR) processes The as-prepared QD-sensitized electrodes were combined with a cobalt complex redox couple [Co(o-phen)3]2+/3+ to make a regenerative liquid-type photovoltaic cell The optimized PbS QD-sensitized solar cells exhibited promising incident photon-to-current conversion efficiency (IPCE) of over 50% and an overall conversion efficiency of 2% at 01 sun in a regenerative mode The overall photovoltaic performance of the PbS QD-sensitized cells was observed to be dependent on the final turn of the SILAR process, giving a better result when the final deposition was Pb2+, not S2- However, in the case of CdS QD-sensitized cells, S2- termination was better than that of Cd2+ The cobalt complex herein used as a regenerative redox couple was found to be more efficient in generating photocurrents from PbS QD cells than the typical hole scavenger Na2S in a
TL;DR: Electrochemical impedance spectroscopy (EIS) and transient voltage decay measurements are applied to compare the performance of dye sensitized solar cells (DSCs) using organic electrolytes, ionic liquids and organic-hole conductors as hole transport materials (HTM).
Abstract: Electrochemical impedance spectroscopy (EIS) and transient voltage decay measurements are applied to compare the performance of dye sensitized solar cells (DSCs) using organic electrolytes, ionic liquids and organic-hole conductors as hole transport materials (HTM). Nano-crystalline titania films sensitized by the some heteroleptic ruthenium complex NaRu(4-carboxylic acid-4'-carboxylate) (4,4'-dinonyl-2,2'-bipyridyl)(NCS)(2), coded Z-907Na are employed as working electrodes. The influence of the nature of the HTM on the photovoltaic figures of merit, that is, the open circuit voltage, short circuit photocurrent and fill factor is evaluated. In order to derive the electron lifetime, as well as the electron diffusion coefficient and charge collection efficiency, EIS measurements are performed in the dark and under illumination corresponding to realistic photovoltaic operating conditions of these mesoscopic solar cells. A theoretical model is established to interpret the frequency response off the impedance under open circuit conditions, which is conceptually similar to photovoltage transient decay measurements. Important information on factors that govern the dynamics of electron transport within the nanocrystalline TiO2 film and charge recombination across the dye sensitized heterojunction is obtained.
TL;DR: In this paper, the bisthienothiophene conjugated linker along with a hydrophobic triphenylamine electron-donor and a hyphilic cyanoacrylic acid electron-acceptor was employed to construct a high molar extinction coefficient organic photosensitizer, exhibiting a power conversion efficiency of 8.0% measured under irradiation of air mass 1.5 global (AM 1 5G) full sunlight.
Abstract: We employed the bisthienothiophene conjugated linker along with a hydrophobic triphenylamine electron-donor and a hydrophilic cyanoacrylic acid electron-acceptor to construct a high molar extinction coefficient organic photosensitizer, exhibiting a power conversion efficiency of 8.0% measured under irradiation of air mass 1.5 global (AM 1.5G) full sunlight.
TL;DR: A negative conduction band shift was observed due to the favorable dipolar field exerted by the JK2 sensitizer to the TiO(2) surface, at variance with heteroleptic Ru(II)-dyes for which an opposite dipole effect was found, providing an increased V(oc).
Abstract: Solid-state dye-sensitized solar cells were fabricated using an organic dye, 2-cyanoacrylic acid-4-(bis-dimethylfluoreneaniline)dithiophene (JK2), which exhibits more than 1 V open-circuit potential (Voc). To scrutinize the origin of high voltage in these cells, transient Voc decay measurements and density functional theroy calculations of the interacting dye/semiconductor surface were performed. A negative conduction band shift was observed due to the favorable dipolar field exerted by the JK2 sensitizer to the TiO2 surface, at variance with heteroleptic Ru(II)-dyes for which an opposite dipole effect was found, providing an increased Voc.
Technical University of Denmark1, Simon Fraser University2, University of Southern California3, National Renewable Energy Laboratory4, University of Denver5, University of Texas at Dallas6, University of North Texas7, University of Florida8, University of Pittsburgh9, Eindhoven University of Technology10, Linköping University11, Katholieke Universiteit Leuven12, IMEC13, École Polytechnique Fédérale de Lausanne14, University of Patras15, Ben-Gurion University of the Negev16, Alcan17
TL;DR: A round robin for the performance of roll-to-roll coated flexible large-area polymer solarcell modules involving 18 different laboratories in Northern America, Europe and Middle East is presented in this paper.
TL;DR: In this article, an optimized unsymmetrical squaraine dye with carboxylic acid as anchoring group is synthesized for dye-sensitized solar cells (DSCs).
Abstract: An optimized unsymmetrical squaraine dye 5-carboxy-2[[3-[(2,3-dihydro-1, 1-dimethyl-3-ethyl-1H-benzo[e]indol-2-ylidene)methyl]-2-hydroxy-4-oxo-2-cyclobuten-1-ylidene]methyl]-3,3-dimethyl-1-octyl-3H-indolium (SQ02) with carboxylic acid as anchoring group is synthesized for dye-sensitized solar cells (DSCs). Although the pi-framework of SQ02 is insignificantly extended compared to its antecessor squaraine dye SQ01, photophysical measurements show that the new sensitizer has a much higher overall conversion efficiency eta of 5.40% which is improved by 20% when compared to SQ01. UV-vis spectroscopy, cyclic voltammetry and time dependent density functional theory calculations are accomplished to rationalize the higher conversion efficiency of SQ02. A smaller optical band gap including a higher molar absorption coefficient leads to improved light harvesting of the solar cell and a broadened photocurrent spectrum. Furthermore, all excited state orbitals relevant for the pi-pi* transition in SQ02 are delocalized over the carboxylic acid anchoring group, ensuring a strong electronic coupling to the conduction band of TiO2 and hence a fast electron transfer.
TL;DR: The first examples of di-branched di-anchoring organic sensitizers were synthesized and used in dye-sensitized solar cells leading to red-shifted IPCE maxima and increased photocurrent when compared to the corresponding mono-branchhed monoanchoring dye, yielding power conversion efficiency of 5.7% with ionic liquid electrolyte as mentioned in this paper.
Abstract: The first examples of di-branched di-anchoring organic sensitizers were synthesized and used in dye-sensitized solar cells leading to red-shifted IPCE maxima and increased photocurrent when compared to the corresponding mono-branched mono-anchoring dye, yielding power conversion efficiency of 5.7% (4.9% with ionic liquid electrolyte) with enhanced stability under 1 sun conditions from the di-anchoring groups.
TL;DR: The photovoltaic data show that the nature of the spacer group plays a significant role in the electron injection from the photo-excited dye into the nanocrystalline TiO(2) semiconductor, the recombination rates and the efficiency of the cells.
Abstract: A series of unsymmetrical zinc phthalocyanines bearing an anchoring carboxylic function linked to the phthalocyanine ring through different spacers were designed for dye-sensitised solar cells (DSSC). The modification of the spacer group allows not only a variable distance between the dye and the nanocrystalline TiO(2), but also a distinct orientation of the phthalocyanine on the semiconductor surface. The photovoltaic data show that the nature of the spacer group plays a significant role in the electron injection from the photo-excited dye into the nanocrystalline TiO(2) semiconductor, the recombination rates and the efficiency of the cells. The incident monochromatic photon-to-current conversion efficiency (IPCE) for phthalocyanines bearing an insulating spacer is as low as 9%, whereas for those with a conducting spacer an outstanding IPCE 80% was obtained.
TL;DR: In this paper, an indolene-based organic dye, termed D149, incorporated in to solid-state dye-sensitized solar cells using 2,2',7,7'- tetrakis(N,N-di-p-methoxypheny-amine)-9,9' - spirobifluorene (spiro-OMeTAD) as the hole transport material is reported.
Abstract: An investigation of the function of an indolene-based organic dye, termed D149, incorporated in to solid-state dye-sensitized solar cells using 2,2',7,7'- tetrakis(N,N-di-p-methoxypheny-amine)-9,9' - spirobifluorene (spiro-OMeTAD) as the hole transport material is reported. Solar cell performance characteristics are unprecedented. under low light levels, with the solar cells delivering up to 70% incident photon-to-current efficiency (IPCE) and over 6% power conversion efficiency as measured under simulated air mass (AM) 1.5 sun light at 1 and 10 mW cm(-2). However, a considerable nonlinearity. in the photocurrent as intensities approach "full sun" conditions is observed and the devices deliver up to 4.2% power conversion efficiency under simulated sun light of 100 mW cm(-2). The influence of dye-loading upon solar cell operation is investigated and the thin films are probed via photoinduced absorption (PIA) spectroscopy, tune-correlated single-photon counting (TCSPC), and photoluminescence quantum efficiency (PLQE) measurements in order to deduce the cause for the non ideal solar cell performance. The data ! suggest that electron transfer from the photoexcited sensitizer into the TiO2 is only between 10 to 50% efficient and that ionization of the photo excited dye via hole transfer directly to spiro-OMeTAD dominates the charge generation process: A persistent dye bleaching signal is also observed and assigned to a remarkably high density of electrons "trapped" within the dye phase, equivalent to 1.8 x 10(17) cm(-3) under full sun illumination. it is believed that this localized space charge build-up upon the sensitizer is responsible for the non-linearity of photocurrent with intensity and nonoptimum solar. cell performance under full sun conditions.
TL;DR: In this paper, two new organic D-π-A dyes featuring electron-rich 3,4-ethylenedioxythiophene- and 2,2′-bis(3,4]-methylenedioxyntiophene)-conjugated linkers, showing a remarkable red-shifting of photocurrent action spectra compared with their thiophene and bithiophene counterparts, were reported.
Abstract: Cost-effective organic sensitizers will play a pivotal role in the future large-scale production and application of dye-sensitized solar cells. Here we report two new organic D-π-A dyes featuring electron-rich 3,4-ethylenedioxythiophene- and 2,2′-bis(3,4-ethylenedioxythiophene)-conjugated linkers, showing a remarkable red-shifting of photocurrent action spectra compared with their thiophene and bithiophene counterparts. On the basis of the 3-{5′-[N,N-bis(9,9-dimethylfluorene-2-yl)phenyl]-2,2′-bis(3,4-ethylenedioxythiophene)-5-yl}-2-cyanoacrylic acid dye, we have set a new efficiency record of 7.6% for solvent-free dye-sensitized solar cells based on metal-free organic sensitizers. Importantly, the cell exhibits an excellent stability, keeping over 92% of its initial efficiency after 1000 h accelerated tests under full sunlight soaking at 60 °C. This achievement will considerably encourage further design and exploration of metal-free organic dyes for higher performance dye-sensitized solar cells. We have also scrutinized the physical origins of the relatively low photocurrent and photovoltage obtained with an ionic liquid electrolyte compared to a volatile acetonitrile-based electrolyte through transient and modulated photoelectrical measurements.
TL;DR: In this article, band-edge movement and charge-transport were investigated in the context of the Web of Science Record created on 2009-12-23, modified on 2017-05-12.
Abstract: Keywords: Band-Edge Movement ; Electron-Transport ; Charge-Transport ; Impedance Spectroscopy ; Conversion Efficiency ; Interfacial Transfer ; Tio2 ; Recombination ; Kinetics ; Acid Reference LPI-ARTICLE-2009-027doi:10.1002/adfm.200900246View record in Web of Science Record created on 2009-12-23, modified on 2017-05-12
TL;DR: The results show that the candidates selected are very promising to provide good performances as sensitizers, in which ZnTPPG is promising to challenge the current photo-electric conversion efficiency record 7.1% of porphyrin-sensitized solar cells.
Abstract: According to the concepts of attribute axis and attribute coordinate system, porphine and 11 kinds of bridge carbon substituted porphyrins as donors and 9 common acceptors A-I have been designed and calculated at the density functional B3LYP level. The substituent effects on the molecular orbital energy levels of the porphyrin derivatives have been discussed and promising donor-acceptor combinations are screened. Several novel zinc metalloporphyrins selected were then calculated by means of the DFT/TDDFT method in THF solvent. The electronic and spectroscopic properties of ZnTPP and the selected novel zinc porphyrin complexes have been investigated as solar cell senstizers. The results show that the candidates selected are very promising to provide good performances as sensitizers, in which ZnTPPG is promising to challenge the current photoelectric conversion efficiency record 7.1% of porphyrin-sensitized solar cells. The concepts of attribute axis and attribute coordinate system are shown very helpful for tuning the molecular properties and the rational design of functional molecules with anticipated good properties.
TL;DR: In this article, a highly efficient heteroleptic ruthenium (II) complex was synthesized and characterized, which when anchored on nanocrystalline TiO2 films exhibited high power conversion efficiency, 10.3%, and incident photon to electron conversion efficiency 87%.
Abstract: A highly efficient heteroleptic ruthenium (II) complex cis-di(thiocyanato)(4,4′-dicarboxylic acid-2,2′-bipyridine)(4,4′-di-(2-(4-ditolylamine phenyl)ethenyl)-2,2′-bipyridine) ruthenium (II) (IJ-1) was synthesized and characterized, which when anchored on nanocrystalline TiO2 films exhibited high power conversion efficiency, 10.3%, and incident photon to electron conversion efficiency, 87%.
TL;DR: Running relay: Incorporating an energy-relay dye (ERD) into the hole transporter of a dye-sensitized solar cell increased power-conversion efficiency by 29 % by extending light harvesting into the blue region.
Abstract: Running relay: Incorporating an energy-relay dye (ERD) into the hole transporter of a dye-sensitized solar cell increased power-conversion efficiency by 29 % by extending light harvesting into the blue region. In the operating mechanism (see picture), absorption of red photons by the sensitizer transfers an electron into TiO2 and a hole into the electrolyte. Blue photons absorbed by the ERD are transferred by FRET to the sensitizer.
TL;DR: It is demonstrated that co-adsorption of dineohexyl bis-(3,3-dimethyl-butyl)-phosphinic acid along with the amphiphilic ruthenium sensitizer Z907Na increased substantially the power output of the cells mainly due to a retardation of interfacial recombination of photo-generated charge carriers.
Abstract: We report a new class of molecular insulators that electronically passivate the surface of nanocrystalline titania films for high performance dye sensitized solar cells (DSC). Using electrical impedance measurements we demonstrate that co-adsorption of dineohexyl bis-(3,3-dimethyl-butyl)-phosphinic acid (DINHOP), along with the amphiphilic ruthenium sensitizer Z907Na increased substantially the power output of the cells mainly due to a retardation of interfacial recombination of photo-generated charge carriers. The use of phosphinates as anchoring groups opens up new avenues for modification of the surface by molecular insulators, sensitizers and other electro-active molecules to realize the desired optoelectronic performance of devices based on oxide junctions.
TL;DR: The chiral stationary phase for high-performance liquid chromatography showed good chiral recognition ability towards various racemates, including Ruthenium Sensitizer and Dendrimers.
Abstract: Keywords: cyclodextrins ; dyes/pigments ; energy conversion ; host-guest systems ; solar cells ; Nanocrystalline Tio2 Films ; Recombination Dynamics ; Charge-Transfer ; Ruthenium Sensitizer ; Molecular Control ; Blocking Layers ; Dendrimers Reference EPFL-ARTICLE-159593doi:10.1002/anie.200902013View record in Web of Science Record created on 2010-11-30, modified on 2017-05-12