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"Jacques, E"
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11% efficiency solid-state dye-sensitized solar cells with copper(II/I) hole transport materials
Solid-state dye-sensitized solar cells currently suffer from issues such as inadequate nanopore filling, low conductivity and crystallization of hole-transport materials infiltrated in the mesoscopic TiO
2
scaffolds, leading to low performances. Here we report a record 11% stable solid-state dye-sensitized solar cell under standard air mass 1.5 global using a hole-transport material composed of a blend of [Cu (4,4′,6,6′-tetramethyl-2,2′-bipyridine)
2
](bis(trifluoromethylsulfonyl)imide)
2
and [Cu (4,4′,6,6′-tetramethyl-2,2′-bipyridine)
2
](bis(trifluoromethylsulfonyl)imide). The amorphous Cu(II/I) conductors that conduct holes by rapid hopping infiltrated in a 6.5 μm-thick mesoscopic TiO
2
scaffold are crucial for achieving such high efficiency. Using time-resolved laser photolysis, we determine the time constants for electron injection from the photoexcited sensitizers Y123 into the TiO
2
and regeneration of the Y123 by Cu(I) to be 25 ps and 3.2 μs, respectively. Our work will foster the development of low-cost solid-state photovoltaic based on transition metal complexes as hole conductors.
Inadequate pore infiltration and low conductivity of hole transporter materials limit the performance of solid-state dye-sensitized solar cells. Using fast charge-exchange Cu(II/I) complexes as part of the hole transporting material, Cao
et al
. overcome these issues to achieve a record photoconversion efficiency of 11%.
Journal Article
Atomic-level passivation mechanism of ammonium salts enabling highly efficient perovskite solar cells
The high conversion efficiency has made metal halide perovskite solar cells a real breakthrough in thin film photovoltaic technology in recent years. Here, we introduce a straightforward strategy to reduce the level of electronic defects present at the interface between the perovskite film and the hole transport layer by treating the perovskite surface with different types of ammonium salts, namely ethylammonium, imidazolium and guanidinium iodide. We use a triple cation perovskite formulation containing primarily formamidinium and small amounts of cesium and methylammonium. We find that this treatment boosts the power conversion efficiency from 20.5% for the control to 22.3%, 22.1%, and 21.0% for the devices treated with ethylammonium, imidazolium and guanidinium iodide, respectively. Best performing devices showed a loss in efficiency of only 5% under full sunlight intensity with maximum power tracking for 550 h. We apply 2D- solid-state NMR to unravel the atomic-level mechanism of this passivation effect.
Various approaches have been developed to push higher the efficiency of halide perovskite solar cells. Here Alharbi et al. show that ammonium salts treatment can reduce the defect density at the perovskite surface and understand the passivation mechanism with 2D-solid state NMR.
Journal Article
فلسفة اللغة
يبلغ هذا الكتاب من الشمولية والتخصصية مدى يدفع إلى الاعتقاد بأنه عشرة كتب في كتاب واحد، فكل فصل من فصوله مستقل بحد ذاته، كوحدة متكاملة تشمل كل الفكر الغربي في المجال الذي يبحث فيه وهذه إحدى ميزاته الكثيرة، إذ يمنح القارىء إمكانية أن يقرأ الفصول من دون أن يتبع تسلسلها، وأن يكتفي بما يهمه منها، دون أن يؤثر ذلك في فهم مضامين الكتاب والمنهجية مزدوجة \"تطور في الزمن وتحليل معمق، ذلك أن الكتاب يجمع تاريخ الأفكار والتيارات وتحليل المفاهيم الدقيقة.
Book
Most Random Gene Expression Signatures Are Significantly Associated with Breast Cancer Outcome
Bridging the gap between animal or in vitro models and human disease is essential in medical research. Researchers often suggest that a biological mechanism is relevant to human cancer from the statistical association of a gene expression marker (a signature) of this mechanism, that was discovered in an experimental system, with disease outcome in humans. We examined this argument for breast cancer. Surprisingly, we found that gene expression signatures-unrelated to cancer-of the effect of postprandial laughter, of mice social defeat and of skin fibroblast localization were all significantly associated with breast cancer outcome. We next compared 47 published breast cancer outcome signatures to signatures made of random genes. Twenty-eight of them (60%) were not significantly better outcome predictors than random signatures of identical size and 11 (23%) were worst predictors than the median random signature. More than 90% of random signatures >100 genes were significant outcome predictors. We next derived a metagene, called meta-PCNA, by selecting the 1% genes most positively correlated with proliferation marker PCNA in a compendium of normal tissues expression. Adjusting breast cancer expression data for meta-PCNA abrogated almost entirely the outcome association of published and random signatures. We also found that, in the absence of adjustment, the hazard ratio of outcome association of a signature strongly correlated with meta-PCNA (R(2) = 0.9). This relation also applied to single-gene expression markers. Moreover, >50% of the breast cancer transcriptome was correlated with meta-PCNA. A corollary was that purging cell cycle genes out of a signature failed to rule out the confounding effect of proliferation. Hence, it is questionable to suggest that a mechanism is relevant to human breast cancer from the finding that a gene expression marker for this mechanism predicts human breast cancer outcome, because most markers do. The methods we present help to overcome this problem.
Journal Article
Apoptosis-induced CXCL5 accelerates inflammation and growth of prostate tumor metastases in bone
During tumor progression, immune system phagocytes continually clear apoptotic cancer cells in a process known as efferocytosis. However, the impact of efferocytosis in metastatic tumor growth is unknown. In this study, we observed that macrophage-driven efferocytosis of prostate cancer cells in vitro induced the expression of proinflammatory cytokines such as CXCL5 by activating Stat3 and NF-κB(p65) signaling. Administration of a dimerizer ligand (AP20187) triggered apoptosis in 2 in vivo syngeneic models of bone tumor growth in which apoptosis-inducible prostate cancer cells were either coimplanted with vertebral bodies, or inoculated in the tibiae of immunocompetent mice. Induction of 2 pulses of apoptosis correlated with increased infiltration of inflammatory cells and accelerated tumor growth in the bone. Apoptosis-induced tumors displayed elevated expression of the proinflammatory cytokine CXCL5. Likewise, CXCL5-deficient mice had reduced tumor progression. Peripheral blood monocytes isolated from patients with bone metastasis of prostate cancer were more efferocytic compared with normal controls, and CXCL5 serum levels were higher in metastatic prostate cancer patients relative to patients with localized prostate cancer or controls. Altogether, these findings suggest that the myeloid phagocytic clearance of apoptotic cancer cells accelerates CXCL5-mediated inflammation and tumor growth in bone, pointing to CXCL5 as a potential target for cancer therapeutics.
Journal Article
A molecular photosensitizer achieves a V oc of 1.24 V enabling highly efficient and stable dye-sensitized solar cells with copper(II/I)-based electrolyte
To develop photosensitizers with high open-circuit photovoltage (V
) is a crucial strategy to enhance the power conversion efficiency (PCE) of co-sensitized solar cells. Here, we show a judiciously tailored organic photosensitizer, coded MS5, featuring the bulky donor N-(2',4'-bis(dodecyloxy)-[1,1'-biphenyl]-4-yl)-2',4'-bis(dodecyloxy)-N-phenyl-[1,1'-biphenyl]-4-amine and the electron acceptor 4-(benzo[c][1,2,5]thiadiazol-4-yl)benzoic acid. Employing MS5 with a copper (II/I) electrolyte enables a dye-sensitized solar cell (DSC) to achieve a strikingly high V
of 1.24 V, with the V
deficit as low as 130 mV and an ideality factor of merely 1.08. The co-sensitization of MS5 with the wider spectral-response dye XY1b produces a highly efficient and stable DSC with the PCE of 13.5% under standard AM1.5 G, 100 mW cm
solar radiation. Remarkably, the co-sensitized solar cell (active area of 2.8 cm
) presents a record PCE of 34.5% under ambient light, rendering it very attractive as an ambient light harvesting energy source for low power electronics.
Journal Article
Unravelling the mechanism of photoinduced charge transfer processes in lead iodide perovskite solar cells
Lead halide perovskites have recently been used as light absorbers in hybrid organic–inorganic solid-state solar cells, with efficiencies as high as 15% and open-circuit voltages of 1 V. However, a detailed explanation of the mechanisms of operation within this photovoltaic system is still lacking. Here, we investigate the photoinduced charge transfer processes at the surface of the perovskite using time-resolved techniques. Transient laser spectroscopy and microwave photoconductivity measurements were applied to TiO
2
and Al
2
O
3
mesoporous films impregnated with CH
3
NH
3
PbI
3
perovskite and the organic hole-transporting material
spiro
-OMeTAD. We show that primary charge separation occurs at both junctions, with TiO
2
and the hole-transporting material, simultaneously, with ultrafast electron and hole injection taking place from the photoexcited perovskite over similar timescales. Charge recombination is shown to be significantly slower on TiO
2
than on Al
2
O
3
films.
Perovskite solar cells are currently generating great interest in the photovoltaics community, but a detailed understanding of why they are so efficient is lacking. Femtosecond laser spectroscopy and microwave photoconductivity measurements now reveal important insights into the photoinduced charge transfer processes and dynamics of such cells.
Journal Article