The ability to reproducibly synthesize nanocrystal (NC) inks with precisely controlled compositions is essential for making efficient kesterite solar cells from NCs. Here we present the results of a ...study on Cu–Zn–Sn–S NCs in which different particle size fractions were collected over a range of reaction times from various starting reagents. From this we have determined the temporal evolution of the NC ink and identified at least two distinct particle populations that form following injection: large particles containing primarily Cu and Zn, and small particles of Cu and Sn. For short reaction times, the extreme compositional heterogeneity between these size fractions makes the average ink composition highly sensitive to changes in reaction time and precipitation procedure. Longer synthesis times produce more consistent inks, with higher yield, and compositions closer to that of the starting reagents. The choice of metal precursor was found to have a minor impact on the composition of the resulting ink compared to the changes with time, even when substituting Ge precursors for Sn precursors. Using this understanding, we demonstrate the ability to produce inks with targeted off-stoichiometric compositions.
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IJS, KILJ, NUK, PNG, UL, UM
Molecular inks based on dimethyl sulfoxide, thiourea (TU), and metal salts have been used to form high optoelectronic quality semiconductors and have led to high power conversion efficiencies for ...solution-processed photovoltaic devices for Cu2ZnSn(S,Se)4 (CZTS), Cu2Zn(Ge,Sn)(S,Se)4 (CZGTS), CuIn(S,Se)2 (CIS), and Cu(In,Ga)(S,Se)2 (CIGS). However, several metal species of interest, including Ag(I), In(III), Ge(II), and Ge(IV), either have low solubility (requiring dilute inks) or lead to precipitation or gelation. Here, we demonstrate that the combination of N,N-dimethylformamide (DMF) and TU has the remarkable ability to form intermediate-stability acid–base complexes with a wide number of metal chloride Lewis acids (CuCl, AgCl, ZnCl2, InCl3, GaCl3, SnCl4, GeCl4, and SeCl4), to give high-concentration stable molecular inks. Using calorimetry, Raman spectroscopy, and solubility experiments, we reveal the important role of chloride transfer and TU to stabilize metal cations in DMF. Methylation of TU is used to vary the strength of the Lewis basicity and demonstrate that the strength of the TU-metal chloride complex formed after DMF evaporation is critical to prevent volatilization of metal containing species. Further, we formulated a sulfur-free molecular ink which was used to deposit crystalline CuInSe2 without selenization that sustains high quasi-Fermi level splitting under constant illumination. Finally, we demonstrate the ability of the DMF-TU molecular ink chemistry to lead to high-photovoltaic power conversion efficiencies and high-open-circuit voltages for solution-processed CIS and CZGTS with power conversion efficiencies of 13.4% and 11.0% and V oc/V oc,SQ of 67% and 63%, respectively.
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The sintering of nanocrystals to form a bulk film is a promising route for the production of low cost Cu2ZnSn(S,Se)4 solar cells. However, very little is known about how the synthesis of the ...nanocrystals impacts the properties of the sintered film or the performance of the resulting photovoltaic device. Here, we present a study in which devices were made from NC inks with different reaction times. Variation in reaction time produces inks with different average size, composition, and compositional heterogeneity. Accounting for the influence of composition, we find that longer NC reaction times result in improved current collection, larger quasi-Fermi level splitting, lower defect concentrations, and higher power conversion efficiency in the selenized devices. The improvements correlate well with the breadth of the x-ray diffraction peaks, suggesting that the longer reaction times result in larger crystalline domain sizes, and that grain boundaries may act as non-radiative recombination sites. Further, the crystalline domain size in the sintered film is proportional to the mean NC size in the ink, suggesting that some interparticle sintering occurs but that the ultimate grain size in the film is dependent on the starting NC size.
•CZTSSe solar cells were made from nanocrystal inks with different reaction times.•We find improved device efficiency with increasing reaction time.•Longer reaction times have lower defect densities in the selenized devices.•The crystalline domain size of selenized films is proportional to the starting NC size.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The sintering of nanocrystals to form a bulk film is a promising route for the production of low cost Cu sub(2)ZnSn(S,Se) sub(4) solar cells. However, very little is known about how the synthesis of ...the nanocrystals impacts the properties of the sintered film or the performance of the resulting photovoltaic device. Here, we present a study in which devices were made from NC inks with different reaction times. Variation in reaction time produces inks with different average size, composition, and compositional heterogeneity. Accounting for the influence of composition, we find that longer NC reaction times result in improved current collection, larger quasi-Fermi level splitting, lower defect concentrations, and higher power conversion efficiency in the selenized devices. The improvements correlate well with the breadth of the x-ray diffraction peaks, suggesting that the longer reaction times result in larger crystalline domain sizes, and that grain boundaries may act as non-radiative recombination sites. Further, the crystalline domain size in the sintered film is proportional to the mean NC size in the ink, suggesting that some interparticle sintering occurs but that the ultimate grain size in the film is dependent on the starting NC size.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The nanostructure of silica and hybrid thin film mesophases templated by phospholipids via an evaporation-induced self-assembly (EISA) process was investigated by grazing-incidence small-angle X-ray ...scattering (GISAXS). Diacyl phosphatidylcholines with two tails of 6 or 8 carbons were found to template 2D hexagonal mesophases, with the removal of lipid from these lipid/silica films by thermal or UV/O3 processing resulting in a complete collapse of the pore volume. Monoacyl phosphatidylcholines with single tails of 10−14 carbons formed 3D micellular mesophases; the lipid was found to be extractable from these 3D materials, yielding a porous material. In contrast to pure lipid/silica thin film mesophases, films formed from the hybrid bridged silsesquioxane precursor bis(triethoxysilyl)ethane exhibited greater stability toward (both diacyl and monoacyl) lipid removal. Ellipsometric, FTIR, and NMR studies show that the presence of phospholipid suppresses siloxane network formation, while actually promoting condensation reactions in the hybrid material. 1D X-ray scattering and FTIR data were found to be consistent with strong interactions between lipid headgroups and the silica framework.
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The fabrication of nanostructured silica films possessing tricontinuous minimal surface mesophases with well-defined framework and pore connectivity remains a difficult task. As a new route to these ...structures, we introduce glycerol monooleate (GMO) as a template for evaporation-induced self-assembly. As deposited, a nanostructured double gyroid phase is formed, as indicated by analysis of grazing-incidence small-angle X-ray scattering data. Removal of GMO by UV/O3 treatment or acid extraction induces a phase change to a nanoporous body-centered structure, which we tentatively identify as based on the IW-P surface. To improve film quality, we add a cosurfactant to the GMO in a mass ratio of 1:10; when this cosurfactant is cetyltrimethylammonium bromide, we find an unusually large pore size (8−12 nm) in acid extracted films, while UV/O3 treated films yield pores of only about 4 nm. Using this pore size dependence on the film processing procedure, we create a simple method for patterning pore size in nanoporous films, demonstrating spatially defined size-selective molecular adsorption.
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Messenger RNA encodes cellular function and phenotype. In the context of human cancer, it defines the identities of malignant cells and the diversity of tumor tissue. We studied 72,501 single-cell ...transcriptomes of human renal tumors and normal tissue from fetal, pediatric, and adult kidneys. We matched childhood Wilms tumor with specific fetal cell types, thus providing evidence for the hypothesis that Wilms tumor cells are aberrant fetal cells. In adult renal cell carcinoma, we identified a canonical cancer transcriptome that matched a little-known subtype of proximal convoluted tubular cell. Analyses of the tumor composition defined cancer-associated normal cells and delineated a complex vascular endothelial growth factor (VEGF) signaling circuit. Our findings reveal the precise cellular identities and compositions of human kidney tumors.
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BFBNIB, NMLJ, NUK, ODKLJ, PNG, SAZU, UL, UM, UPUK
Molecular inks based on dimethyl sulfoxide, thiourea, and metal salts have been used to form high optoelectronic quality semiconductors and have led to high power conversion efficiencies for ...solution-processed photovoltaic devices for Cu2ZnSn(S,Se)4 (CZTS), Cu2Zn(Ge,Sn)(S,Se)4 (CZGTS), CuIn(S,Se)2 (CIS) and Cu(In,Ga)(S,Se)2 (CIGS). However, several metal species of interest including Ag(I), In(III), Ge(II), and Ge(IV) have either low solubility (requiring dilute inks) or lead to precipitation or gelation. Here, we demonstrate that the combination of N,N-dimethylformamide (DMF) and thiourea (TU) has the remarkable ability to form intermediate-stability acid-base complexes with a wide number of metal chloride Lewis acids (CuCl, AgCl, ZnCl2, InCl3, GaCl3, SnCl4, GeCl4, and SeCl4) to form high-concentration stable molecular inks. Using calorimetry, Raman spectroscopy, and solubility experiments, we reveal the important role of chloride transfer and thiourea to stabilize metal cations in DMF. Methylation of thiourea is used to vary the strength of the Lewis basicity and demonstrate that the strength of the thiourea-metal chloride complex formed after DMF evaporation is critical to prevent volatilization of metal containing species. Further, we formulated a sulfur-free molecular ink which was used to deposit crystalline CuInSe2 without selenization that sustains high quasi-Fermi level splitting under constant illumination. Finally, we demonstrate the ability of the DMF-TU molecular ink chemistry to lead to high photovoltaic power conversion efficiencies and high open-circuit voltages for solution-processed CIS and CZGTS with PCE's of 13.4% and 11.0% and Voc/Voc,SQ of 67% and 63%, respectively.
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We present a photoluminescence study of a high-throughput experiment in which nanocrystal inks of different composition are mixed to produce a continuous composition gradient. Using this technique we ...have produced films in which the cation ratios of a CZTSSe absorber layer are continuously varied laterally on the substrate. Here we report the compositional dependence of peak intensity, position, and peak shift with intensity as a function of composition.
Undifferentiated sarcomas (USARCs) of adults are diverse, rare, and aggressive soft tissue cancers. Recent sequencing efforts have confirmed that USARCs exhibit one of the highest burdens of ...structural aberrations across human cancer. Here, we sought to unravel the molecular basis of the structural complexity in USARCs by integrating DNA sequencing, ploidy analysis, gene expression, and methylation profiling. We identified whole genome duplication as a prevalent and pernicious force in USARC tumorigenesis. Using mathematical deconvolution strategies to unravel the complex copy-number profiles and mutational timing models we infer distinct evolutionary pathways of these rare cancers. In addition, 15% of tumors exhibited raised mutational burdens that correlated with gene expression signatures of immune infiltration, and good prognosis.
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•Undifferentiated sarcomas contain biologically relevant molecular subgroups•Identification of mismatch repair deficiency open up alternate avenues for therapy•Pseudohaploidization is a recurrent event in undifferentiated sarcomas•Copy-number signatures are useful for inferring states of sarcoma evolution
Steele et al. determine the molecular landscape of undifferentiated sarcomas. They identify tumors with high mutation burdens, which are enriched for activation of immune pathways and have good prognoses, and deduce four tumorigenic routes, all of which begin with driver mutations before whole genome duplication.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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