All-Inorganic Cesium-Based Hybrid Perovskites for Efficient and Stable Solar Cells and Modules

AbstractIn the last ten years, organic–inorganic hybrid perovskites have been skyrocketing the field of innovative photovoltaics (PVs) and now represent one of the most promising solution for next‐generation PVs. Within the family of halide perovskites, increasing attention has been focused on the so‐called all‐inorganic group, where the organic cation is replaced by cesium, as in the case of CsPbI3. This subclass of halide perovskites features desirable optoelectronic properties such as easily tunable bandgap, strong defect tolerance, and improved thermal stability compared to the hybrid systems. When integrated in PV cells, they exhibit high power conversion efficiency (PCE) with record values of 19.03%. However, all‐inorganic perovskite solar cells (PCSs) face several challenges such as i) instability of the CsPbI3 photoactive phase in ambient conditions, ii) inhomogeneous film morphology, and iii) high surface defect density. This work focuses on the mentioned challenges with a special attention on discussing the Cs–Pb–X system (X = I, Br). Then, the most recent and effective approaches for increasing both the PCE and the stability of devices are reviewed, which include material doping, interface engineering, and device optimization. Finally, the first efforts toward the upscaling of Cs‐based PSCs, and predicted methods for enabling large‐scale production, are discussed

Direct Arylation Strategies in the Synthesis of π-Extended Monomers for Organic Polymeric Solar Cells

π-conjugated macromolecules for organic polymeric solar cells can be rationally engineered at the molecular level in order to tune the optical, electrochemical and solid-state morphology characteristics, and thus to address requirements for the efficient solid state device implementation. The synthetic accessibility of monomers and polymers required for the device is getting increasing attention. Direct arylation reactions for the production of the π-extended scaffolds are gaining importance, bearing clear advantages over traditional carbon-carbon forming methodologies. Although their use in the final polymerization step is already established, there is a need for improving synthetic accessibility to implement them also in the monomer synthesis. In this review, we discuss recent examples highlighting this useful strategy

Origin of Charge Separation at Organic Photovoltaic Heterojunctions: A Mesoscale Quantum Mechanical View

The high efficiency of charge generation within organic photovoltaic blends apparently contrasts with the strong “classical” attraction between newly formed electron–hole pairs. Several factors have been identified as possible facilitators of charge dissociation, such as quantum mechanical coherence and delocalization, structural and energetic disorder, built-in electric fields, and nanoscale intermixing of the donor and acceptor components of the blends. Our mesoscale quantum-chemical model allows an unbiased assessment of their relative importance, through excited-state calculations on systems containing thousands of donor and acceptor sites. The results on several model heterojunctions confirm that the classical model severely overestimates the binding energy of the electron–hole pairs, produced by vertical excitation from the electronic ground state. Using physically sensible parameters for the individual materials, we find that the quantum mechanical energy difference between the lowest interfacial charge transfer states and the fully separated electron and hole is of the order of the thermal energy

Conjugated Thiophene-Fused Isatin Dyes through Intramolecular Direct Arylation

We report on the design, synthesis, and properties of innovative, planar, π-conjugated compounds in which a thiophene ring is fused with the skeleton of the naturally occurring dye isatin. The synthesis is achieved in high yields making use of an intramolecular direct arylation reaction as the key step, making the overall process potentially scalable. The synthetic sequence has been demonstrated also for an isatin bearing fluorine substituents on the aromatic ring. NMR and X-ray studies demonstrate the crosstalk occurring between the fused, coplanar, and conjugated moieties, making these novel dyes with a donor–acceptor character. Cyclic voltammetry and UV–vis studies confirm very interesting HOMO–LUMO levels and energy gaps for the new compounds

Topological flat bands in frustrated kagome lattice CoSn

Electronic flat bands in momentum space, arising from strong localization of electrons in real space, are an ideal stage to realize strong correlation phenomena. In certain lattices with built-in geometrical frustration, electronic confinement and flat bands can naturally arise from the destructive interference of electronic hopping pathways. Such lattice-borne flat bands are often endowed with nontrivial topology if combined with spin-orbit coupling, while their experimental realization in condensed matter system has been elusive so far. Here, we report the direct observation of topological flat bands in the vicinity of the Fermi level in frustrated kagome system CoSn, using angle-resolved photoemission spectroscopy and band structure calculations. The flat band manifests itself as a dispersionless electronic excitation along the G-M high symmetry direction, with an order of magnitude lower bandwidth (below 150 meV) compared to the Dirac bands originating from the same orbitals. The frustration-driven nature of the flat band is directly confirmed by the real-space chiral d-orbital texture of the corresponding effective Wannier wave functions. Spin-orbit coupling opens a large gap of 80 meV at the quadratic band touching point between the Dirac and flat bands, endowing a nonzero Z2 topological invariant to the flat band in the two-dimensional Brillouin zone. Our observation of lattice-driven topological flat band opens a promising route to engineer novel emergent phases of matter at the crossroad between strong correlation physics and electronic topology.Comment: 19 pages, 4 figure

Atomistic modelling of entropy driven phase transitions between different crystal modifications in polymers: the case of poly(3-alkylthiophenes)

Polymorphism and related solid-state phase transitions affect the structure and morphology and hence the properties of materials, but they are not-so-well understood. Atomistic computational methods can provide molecular-level insights, but they have rarely proven successful for transitions between polymorphic forms of crystalline polymers. In this work, we report atomistic molecular dynamics (MD) simulations of poly(3-alkylthiophenes) (P3ATs), widely used organic semiconductors to explore the experimentally observed, entropy-driven transition from form II to more common form I type polymorphs, or, more precisely, to form I mesophases. The transition is followed continuously, also considering X-ray diffraction evidence, for poly(3-hexylthiophene) (P3HT) and poly(3-butylthiophene) (P3BT), evidencing three main steps: (i) loss of side chain interdigitation, (ii) partial disruption of the original stacking order and (iii) reorganization of polymer chains into new, tighter, main-chain stacks and new layers with characteristic form I periodicities, substantially larger than those in the original form II. The described approach, likely applicable to other important transitions in polymers, provides previously inaccessible insight into the structural organization and disorder features of form I structures of P3ATs, not only in their development from form II structures but also from melts or solutions

Transvesical endoscopic port in abdominal surgery: an updated perspective

Transvesical endoscopic port in abdominal surgery: an updated perspective.Natural orifice transluminal endoscopic surgery (NOTES) generated a huge hope among surgeons because it promised scarless surgery and eventually less pain and surgical stress. However, serious limitations regarding reliable visceral closing methods remain unsolved. This article provides an update in development and future applications of transvesical access in the field of surgery.(undefined

Familial breast cancer: characteristics and outcome of BRCA 1–2 positive and negative cases

BACKGROUND: The clinical and pathological characteristics and the clinical course of patients with breast cancer and BRCA 1–2 mutation are poorly known. METHODS: From 1997, patients with breast cancer and a family history of breast or ovarian cancer were offered BRCA testing. The clinical and pathological features of patients with known BRCA status were retrospectively assessed and comparisons were made between cancers arising in BRCA positive and BRCA wild type (WT) patients respectively. Type of treatment, pattern of relapse, event (local relapse, contralateral breast cancer, metastases) free and overall survival were also compared in the two groups. Out of the 210 patients tested, 125 had been treated and followed-up at our Institution and were evaluated in this study. RESULTS: BRCA positive patients tended to be more often premenopausal (79% vs 65%) and to have positive lymphnodes (63% vs 49%), poorly differentiated tumours (76% vs 40% – p = 0.002 at univariate analysis, not significant at multivariate analysis) and negative estrogen receptors (43% vs 29%). Treatment was not different in the two groups. In the 86 BRCA-WT patients, the first event was a local relapse in 3 (3%), metachronous contralateral breast cancer in 7 (8%) and distant metastases in 16 (19%). In the 39 BRCA positive patients, the corresponding figures were 3 (8%), 8 (21%) and 3 (8%). There was no difference in event free survival, with a median of 180 months in both groups of patients. At 20 years, projected survival was 85% for BRCA positive patients and 55% for BRCA-WT, but this difference was not statistically significant. CONCLUSION: Although BRCA positive patients have more frequently negative prognostic factors, their prognosis appears to be equal to or better than in patients with BRCA-WT

TAO Conceptual Design Report: A Precision Measurement of the Reactor Antineutrino Spectrum with Sub-percent Energy Resolution

The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A ton-level liquid scintillator detector will be placed at about 30 m from a core of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be measured with sub-percent energy resolution, to provide a reference spectrum for future reactor neutrino experiments, and to provide a benchmark measurement to test nuclear databases. A spherical acrylic vessel containing 2.8 ton gadolinium-doped liquid scintillator will be viewed by 10 m^2 Silicon Photomultipliers (SiPMs) of >50% photon detection efficiency with almost full coverage. The photoelectron yield is about 4500 per MeV, an order higher than any existing large-scale liquid scintillator detectors. The detector operates at -50 degree C to lower the dark noise of SiPMs to an acceptable level. The detector will measure about 2000 reactor antineutrinos per day, and is designed to be well shielded from cosmogenic backgrounds and ambient radioactivities to have about 10% background-to-signal ratio. The experiment is expected to start operation in 2022