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The manufacturing of clean energy technologies has become a global enterprise. An analysis of four clean energy technology manufacturing processes—wind turbine components, crystalline silicon solar photovoltaic modules, light-duty vehicle lithium-ion battery cells, and light-emitting diodes—was conducted to provide a reference point for comparison over time as this sector evolves. The manufacturing supply chain analysis included processing of raw materials, making required subcomponents, and assembling final products, using benchmarks that crossed 12 economies: Brazil, Canada, China, Germany, India, Japan, Malaysia, Mexico, South Korea, Republic of China (Taiwan), the United Kingdom, and the United States. Larger economies, with extensive manufacturing supply chains and high prevailing wages, tend to retain more value added from clean energy manufacturing than small economies. Manufacturing of clean energy technologies drives extensive trade among economies to support the widely distributed supply chain links. Production of wind turbine components and photovoltaic modules is more centralized than production of light-emitting diodes and lithium-ion battery cells. Across the four clean energy technologies evaluated, there was generally an excess of manufacturing capacity relative to global supply.

Semiconductor nanocrystals are promising materials for printed optoelectronic devices, but their high surface areas are susceptible to forming defects that hinder charge carrier transport. Furthermore, correlation of chalcogenide nanocrystal (NC) material properties with solar cell operation is not straightforward due to the disorder often induced into NC fiduring processing. Here, an improvement in long-range ordering of PbSe NCs symmetry that results from halide surface passivation is described, and the effects on chemical, optical, and photovoltaic device properties are investigated. Notably, this passivation method leads to a nanometer-scale rearrangement of PbSe NCs during ligand exchange, improving the long-range ordering of nanocrystal symmetry entirely with inorganic surface chemistry. Solar cells constructed with a variety of architectures show varying improvement and suggest that triplet formation and ionization, rather than carrier transport, is the limiting factor in singlet fi ssion solar cells. Compared to existing protocols, our synthesis leads to PbSe nanocrystals with surface-bound chloride ions, reduced sub-bandgap absorption and robust materials and devices that retain performance characteristics many hours longer than their unpassivated counterparts.

The efficient transfer of energy between organic and inorganic semiconductors is a widely sought after property, but has so far been limited to the transfer of spin-singlet excitons. Here we report efficient resonant-energy transfer of molecular spin-triplet excitons from organic semiconductors to inorganic semiconductors. We use ultrafast optical absorption spectroscopy to track the dynamics of triplets, generated in pentacene through singlet exciton fission, at the interface with lead selenide (PbSe) nanocrystals. We show that triplets transfer to PbSe rapidly (

We present two-dimensional Fourier transform optical spectroscopy measurements of two types of molecular J-aggregate thin films and show that temperature-dependent dynamical effects govern exciton delocalization at all temperatures, even in the presence of significant inhomogeneity. Our results indicate that in the tested molecular aggregates, even when the static structure disorder dominates exciton dephasing dynamics, the extent of exciton delocalization may be limited by dynamical fluctuations, mainly exciton-phonon coupling. Thus inhomogeneous dephasing may mediate the exciton coherence time whereas dynamical fluctuations mediate the exciton coherence length.

We report the formation and photonic properties of CdSe/ZnS quantum dot (QD)/J-aggregate donor−acceptor Forster resonant energy transfer (FRET) pairs that are electrostatically bound and dispersed in water. Assembly occurs when the positively charged dye, 1,1′,3,3′-tetraethyl-5,5′,6,6′-tetrachlorobenzimidazolocarbocyanine (TTBC), binds electrostatically to QDs that are coated with a negatively charged amphiphilic polymer. QD/J-aggregate FRET pairs display the broadband absorption in the visible and the ultraviolet (UV) part of the spectrum typical of quantum dots, along with the narrow emission linewidths characteristic of J-band emitters (∼12 nm full width at half-maximum). We use dynamic light scattering, transmission electron microscopy, photoluminescence spectroscopy, and photoluminescence lifetimes to conclude that the size of the aggregates formed in the presence of QDs is between 1−6 nm. We find the FRET radius of the QD/J-aggregate to be 5.1 nm. We further demonstrate electrostatic binding as a ge...

Singlet exciton fission is the spin-conserving transformation of one spin-singlet exciton into two spin-triplet excitons. This exciton multiplication mechanism offers an attractive route to solar cells that circumvent the single-junction Shockley-Queisser limit. Most theoretical descriptions of singlet fission invoke an intermediate state of a pair of spin-triplet excitons coupled into an overall spin-singlet configuration, but such a state has never been optically observed. In solution, we show that the dynamics of fission are diffusion limited and enable the isolation of an intermediate species. In concentrated solutions of bis(triisopropylsilylethynyl)[TIPS]--tetracene we find rapid (

We report the simultaneous observation of geminate and nongeminate triplet-triplet annihilation in a solution-processable small molecule TIPS-tetracene undergoing singlet exciton fission. Using optically detected magnetic resonance, we identify recombination of triplet pairs directly following singlet fission, as well as recombination of triplet excitons undergoing bimolecular triplet-triplet annihilation. We show that the two processes give rise to distinct magnetic resonance spectra, and estimate the interaction between geminate triplet excitons to be 60 neV.

Singlet exciton fission, the spin-conserving process that produces two triplet excited states from one photoexcited singlet state, is a means to circumvent the Shockley-Queisser limit in single-junction solar cells. Although the process through which singlet fission occurs is not well characterized, some local order is thought to be necessary for intermolecular coupling. Here, we report a triplet yield of 200% and triplet formation rates approaching the diffusion limit in solutions of bis(triisopropylsilylethynyl (TIPS)) pentacene. We observe a transient bound excimer intermediate, formed by the collision of one photoexcited and one ground-state TIPS-pentacene molecule. The intermediate breaks up when the two triplets separate to each TIPS-pentacene molecule. This efficient system is a model for future singlet-fission materials and for disordered device components that produce cascades of excited states from sunlight.

Recent research has pushed the efficiency of colloidal quantum dot solar cells toward a level that spurs commercial interest. Quantum dot/metal oxide bilayers form the most efficient colloidal quantum dot solar cells, and most studies have advanced the understanding of the quantum dot component. We study the interfacial recombination process in depleted heterojunction colloidal quantum dot (QD) solar cells formed with ZnO as the oxide by varying (i) the carrier concentration of the ZnO layer and (ii) the density of intragap recombination sites in the QD layer. We find that the open-circuit voltage and efficiency of PbS QD/ZnO devices can be improved by 50% upon doping of the ZnO with nitrogen to reduce its carrier concentration. In contrast, doping the ZnO did not change the performance of PbSe QD/ZnO solar cells. We use X-ray photoemission spectroscopy, ultraviolet photoemission spectroscopy, transient photovoltage decay measurements, transient absorption spectroscopy, and intensity-dependent photocurrent measurements to investigate the origin of this effect. We find a significant density of intragap states within the band gap of the PbS quantum dots. These states facilitate recombination at the PbS/ZnO interface, which can be suppressed by reducing the density of occupied states in the ZnO. For the PbSe QD/ZnO solar cells, where fewer intragap states are observed in the quantum dots, the interfacial recombination channel does not limit device performance. Our study sheds light on the mechanisms of interfacial recombination in colloidal quantum dot solar cells and emphasizes the influence of quantum dot intragap states and metal oxide properties on this loss pathway.

Pure diasteriomers, obtained simply and directly by reaction of hypophosphorous acid salts of (R)(+) or (S)(−) - N-α-methylbenzylamine with aldehydes, can be simultaneously deprotected and oxidised in one step to provide a highly convenient synthesis of α - aminophosphonic acids in high optical purity.

Singlet exciton fission-sensitized solar cells have the potential to exceed the Shockley-Queisser limit by generating additional photocurrent from high-energy photons. Pentacene is an organic semiconductor that undergoes efficient singlet fission--the conversion of singlet excitons into pairs of triplets. However, the pentacene triplet is non-emissive, and uncertainty regarding its energy has hindered device design. Here we present an in situ measurement of the pentacene triplet energy by fabricating a series of bilayer solar cells with infrared-absorbing nanocrystals of varying bandgaps. We show that the pentacene triplet energy is at least 0.85 eV and at most 1.00 eV in operating devices. Our devices generate photocurrent from triplets, and achieve external quantum efficiencies up to 80%, and power conversion efficiencies of 4.7%. This establishes the general use of nanocrystal size series to measure the energy of non-emissive excited states, and suggests that fission-sensitized solar cells are a favourable candidate for third-generation photovoltaics.

We present the first semiconductor nanocrystal films of nanoscale dimensions that are electrically conductive and crack-free. These films make it possible to study the electrical properties intrinsic to the nanocrystals unimpeded by defects such as cracking and clustering that typically exist in larger-scale films. We find that the electrical conductivity of the nanoscale films is 180 times higher than that of drop-cast, microscopic films made of the same type of nanocrystal. Our technique for forming the nanoscale films is based on electron-beam lithography and a lift-off process. The patterns have dimensions as small as 30 nm and are positioned on a surface with 30 nm precision. The method is flexible in the choice of nanocrystal core-shell materials and ligands. We demonstrate patterns with PbS, PbSe, and CdSe cores and Zn(0.5)Cd(0.5)Se-Zn(0.5)Cd(0.5)S core-shell nanocrystals with a variety of ligands. We achieve unprecedented versatility in integrating semiconductor nanocrystal films into device structures both for studying the intrinsic electrical properties of the nanocrystals and for nanoscale optoelectronic applications.

Serine phosphonate isosteres (7), suitably protected for direct use in peptide synthesis, have been prepared from vinylphosphonate diesters in three steps and high overall yield.

We report a 20-fold enhancement in the fluorescence of the organic dye DCM when resonantly coupled to a strongly optically absorbing structure of a thin film of spin-deposited molecular J-aggregates in a critically coupled resonator (JCCR) geometry. A submonolayer equivalent of DCM molecules is shown to absorb and re-emit 2.2% of the incident resonant photons when coupled to the JCCR enhancement structure, compared to 0.1% for the bare film of same thickness on quartz. Such a JCCR structure is a general energy focusing platform that localizes over 90% of incident light energy within a 15 nm thin film layer in the form of excitons that can subsequently be transferred to colocated lumophores. Applications of the exciton-mediated concentration of optical energy are discussed in the context of solid-state lighting, photodetection, and single photon optics.

J-aggregates are ordered clusters of coherently coupled molecular dyes, (1) and they have been used as light sensitizers in film photography due to their intense absorptions. Hybrid structures containing J-aggregates may also have applications in devices that require spectral specificity, such as color imaging or optical signaling. (2) However the use of J-aggregates in optoelectronic devices has posed a long-standing challenge (3, 4) due to the difficulty of controlling aggregate formation and the low charge carrier mobility of many J-aggregates in solid state. In this paper, we demonstrate a modular method to assemble three different cyanine J-aggregates onto CdSe nanowires, resulting in a photodetector that is color-sensitized in three specific, narrow absorption bands. Both the J-aggregate and nanowire device components are fabricated from solution and the sensitizing wavelength is switched from blue to red to green, using only solution-phase exchange of the J-aggregates on the same underlying device.

We present the synthesis of Cd(3)As(2) colloidal quantum dots luminescent from 530 to 2000 nm. Previous reports on quantum dots emitting in the infrared are primarily limited to the lead chalcogenides and indium arsenide. This work expands the availability of high quality infrared emitters.

A 3-step synthesis to the title compounds has been developed which provides them differentially protected at nitrogen. These could then be selectively deprotected using hydrazine hydrate or hydrogenolysis over Pd/C.

Diphenyl phosphonate ester analogues of phenylalanine and peptides derived from these have been prepared and are shown to specifically inhibit chymotrypsin. Phosphonate isosters of serine and tyrosine phosphates appropriately protected for use in peptide synthesis have been prepared.

This paper describes the solution preparation of thin films composed of quantum dots and thiacyanine J-aggregates, making use of the size tunable emission of quantum dots and the narrow, intense absorption of J-aggregates in the solid state. These blended films exhibit 90% energy transfer efficiency from J-aggregates to quantum dots and can uniformly cover a large area. Because the presence of the J-aggregates enhances the QD photoluminescence intensity by 2.5-fold over QDs alone, these solid state materials may be useful in downconversion applications or in fundamental investigations of light harvesting.

Diphenyl phosphonate ester analogues of phenylalanine and peptides derived from these have been prepared and are shown to specifically inhibit chymotrypsin. Phosphonate isosters of serine and tyrosine phosphates appropriately protected for use in peptide synthesis have been prepared.

A 3-step synthesis to the title compounds has been developed which provides them differentially protected at nitrogen. These could then be selectively deprotected using hydrazine hydrate or hydrogenolysis over Pd/C.

Serine phosphonate isosteres (7), suitably protected for direct use in peptide synthesis, have been prepared from vinylphosphonate diesters in three steps and high overall yield.

Pure diasteriomers, obtained simply and directly by reaction of hypophosphorous acid salts of (R)(+) or (S)(−) - N-α-methylbenzylamine with aldehydes, can be simultaneously deprotected and oxidised in one step to provide a highly convenient synthesis of α - aminophosphonic acids in high optical purity.

The synthesis of α-aminophosphonate analogues of tyrosine and tryptophan, e.g. 4 and 5 respectively, and their incorporation into proline-containing dipeptides is reported; of the sequences synthesised, the dipeptide Z-Pro-TrpP(OPh)2 is the only derivative that functions as an irreversible inactivator of the serine proteinase chymotrypsin, in contrast, the tyrosine analogue 4 behaves as a competitive reversible inhibitor of the enzyme and the tryptophan analogue 5 behaves as a slow-binding inhibitor.

The synthesis of diphenyl phosphonate analogues of aspartic and glutamic acid, and their inhibitory activity against S. aureus Vg protease and granzyme B, is described. The study has revealed diiculties with protecting group compatibility in the synthesis of these analogues. Two analogues, Acetyl.AspP(OPh)2 and Acetyl.GluP(OPh)2 were found to function as irreversible inactivators of V8 proteinase, yet exhibit no activity against granzyme B. 0 1998 Elsevier Science Ltd. All rights reserved.

The molecular mechanism of InP colloidal quantum dot (QD) syntheses was investigated by NMR spectroscopy. Unlike methods for monodisperse PbSe and CdSe, existing InP syntheses result in total depletion of molecular phosphorous species following nucleation, so QD growth is due exclusively to non-molecular ripening. Amines inhibit precursor depletion by solvation (see picture), contrary to previous reports., MIT-Harvard Center for Cancer Nanotechnology Excellence (National Institutes of Health (U.S.) 1U54-CA119349), United States. Army Research Office (ISN W911NF-07-D-0004), Massachusetts Institute of Technology. Dept. of Chemistry Instrumentation Facility (CHE-980806), Massachusetts Institute of Technology. Dept. of Chemistry Instrumentation Facility (DBI-9729592), National Science Foundation (U.S.). Graduate Research Fellowship Program

We report narrow-band absorption enhancement of semiconductor nanocrystals via Forster resonance energy transfer from cyanine J-aggregates. These J-aggregated dyes associate electrostatically with short quantum-dot (QD) surface ligands in solution. Energy transfer efficiencies approach unity for this light sensitization and result in a 5-fold enhancement in the QD excitation near the J-aggregate absorption maximum. Because a thin layer of J-aggregates attenuates the same amount of light (at peak absorbance) as a far thicker film of monomer dye, these absorption-enhanced materials may have applications in light-sensitizing applications such as photodetection and optical down-conversion.

A statistical mechanical analysis of an isotropic, spatially frustrated Ising model is presented. Information from Monte Carlo simulation, low-temperature series and the ϵ-expansion is used to construct the global phase diagram of the model. Whilst this combination of statistical mechanical techniques has been helpful, we also stress the limitations in studies of this type. We discuss the techniques of parallelization and vectorization as applied to simulations of lattice spin models. Where possible, we have made suggestions which may be of help in further elucidating the properties of the lattice model of microemulsions.

[reaction: see text] On the basis of reaction rate data, we have proposed a new mechanism for the Baylis-Hillman reaction involving the formation of a hemiacetal intermediate. We have determined that the rate-determining step is second order in aldehyde and first order in DABCO and acrylate. We have shown that this mechanism is general to aryl aldehydes under polar, nonpolar, and protic conditions using both rate data and two isotope effect experiments.

Nature Chemistry 5, 1019–1024 (2013); published online 17 November 2013; corrected after print 21 November 2013. In the version of this Article originally published, the colour scales on Figs 2 and 4 were incorrect. These have now been corrected in the online versions of the Article.

We report single-particle photoluminescence (PL) intermittency (blinking) with high on-time fractions in colloidal CdSe quantum dots (QD) with conformal CdS shells of 1.4 nm thickness, equivalent to approximately 4 CdS monolayers. All QDs observed displayed on-time fractions > 60% with the majority > 80%. The high-on-time-fraction blinking is accompanied by fluorescence quantum yields (QY) close to unity (up to 98% in an absolute QY measurement) when dispersed in organic solvents and a monoexponential ensemble photoluminescence (PL) decay lifetime. The CdS shell is formed in high synthetic yield using a modified selective ion layer adsorption and reaction (SILAR) technique that employs a silylated sulfur precursor. The CdS shell provides sufficient chemical and electronic passivation of the QD excited state to permit water solubilization with greater than 60% QY via ligand exchange with an imidazole-bearing hydrophilic polymer.

α-Aminoalkylphosphonic acids are analogues of natural aminoacids and as such have been the subject of much research effort over past years1. The diphenyl esters of α- aminoalkylphosphonic acids are particularly potent and show high selectivity as irreversible inhibitors of serine proteinases. Thus far, α-aminoalkylphosphonic acid ester analogues of a number of aliphatic- and aromatic aminoacids have been prepared including valine, phenylalanine, tryptophan, and tyrosine2, and the basic aminoacids ornithine, lysine. etc.3. We have now also prepared the a-diphenyl phosphonate analogues of the acidic aminoacids, aspartic and glutamic4. These have been examined as potential inactivators of serine proteinases exhibiting a P1 specificity for aspartate and glutamate, e.g. S. aureus V8 protease and granzyme B.

The synthesis of α-aminophosphonate analogues of tyrosine and tryptophan, e.g. 4 and 5 respectively, and their incorporation into proline-containing dipeptides is reported; of the sequences synthesised, the dipeptide Z-Pro-TrpP(OPh)2 is the only derivative that functions as an irreversible inactivator of the serine proteinase chymotrypsin, in contrast, the tyrosine analogue 4 behaves as a competitive reversible inhibitor of the enzyme and the tryptophan analogue 5 behaves as a slow-binding inhibitor.

The purpose of this exploratory study was to investigate the relationship between participation in Marriage Encounter, the largest marriage enrichment program in the world, and subsequent marital or family distress. Analyzing 13 case reports from seven marital therapists, the authors suggest that Marriage Encounter weekends can cause marital or family deterioration for some couples through increased marital conflict, avoidance of constructive problem solving, or marital enmeshment at the expense of children. It appears that the most harmful aspect of the Marriage Encounter experience is its induction of intense couple-centered communication, leading to emotional overload in some couples. The authors offer several recommendations intended to lower the risks associated with participation in Marriage Encounter.

The reaction of sodium methylphenylphosphide with (+)-(R)-1-chloroethylbenzene gives (–)-(SP)-(SC)-α-methylbenzylmethylphenylphosphine oxide after oxidation; the optical purities at phosphorus and carbon have been determined.

Activated olefins, HR1CCR1H (R1= CO2Me or COPh), are reduced rapidly and stoicheiometrically by some alkyl phosphines, PR32, (R2= Et, Prn, or Bun), both free and initially bound to cobalt, in anhydrous methanol; the reaction proceeds by the formation of an ylide.

The addition of ethyl NN-dichlorocarbamate or NN-dichlorophosphoramidates to five-membered cyclic alkenes at 0 °C is stereospecific and cis; these results are conveniently explained by a 1,3-atom shift mechanism.

Methyltriphenoxyphosphonium trifluoromethanesulphonate is used to synthesise a variety of compound types including ethers, esters, nitriles, and diols and in a novel reduction of alkenes to alkanes.

The reaction of sodium methylphenylphosphide with (+)-(R)-1-chloroethylbenzene gives (–)-(SP)-(SC)-α-methylbenzylmethylphenylphosphine oxide after oxidation; the optical purities at phosphorus and carbon have been determined.

cis- and trans- Isomers of derivatives of 3-halogenoacrylic acids undergo nucleophilic displacement reactions with triphenylphosphine, tri-n-butylphosphine, and triethyl phosphite to produce the correspondingtrans-vinyl-phosphonium salts and -phosphonates exclusively. 1H n.m.r.spectra are reported for these compounds. The mechanism of the displacement reaction is discussed.