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A triple helicene based molecular semiconductor with a high glass transition temperature enables the fabrication of perovskite solar cells with 22.1% efficiency which are stable at 85 °C.

The poor tolerance of ionic perovskite light-absorption layers to water vapor, thermal stress, and bias potential poses remarkable challenges for the selection of other essential elements of solar ...

The application of exotic conjugated skeletons in organic semiconductors is alluring due to the topology related optoelectronic peculiarities. In this paper we explore the design of molecular semiconductors starting from the saddle-shaped o-tetraphenylene (OTP) for the first time. The in silico tailored molecular semiconductor OTPE-OMeTPA with extended π-conjugation presents an improved hole mobility in comparison with its counterpart OTP-OMeDPA, due to the reduced reorganization energy and the larger intermolecular centroid distance. Molecular dynamics simulations clarify the atomic-scale microscopic origins of glass transition in the pristine materials and their p-doping promotor containing composites, being associated with the torsional motion of central OTP and the translational motion of all centroids, respectively. The OTPE-OMeTPA based organic composite displays desirable combined properties of conductivity, glass transition temperature, solution processibility, and interfacial charge transfer kinetics, allowing for the fabrication of thermostable perovskite solar cells with 21.5% power conversion efficiency. A comprehensive comparison of device degradation is also performed by joint experimental measurements and theoretical modeling, laying a solid foundation for further materials and device development.

This paper examines how cross-listing of Chinese A- and Hong Kong H-shares (AH cross-listed) affects the value of corporate cash holdings. Using a sample of AH cross-listed firms, we find that the value of cash holdings is higher for cross-listed than for non-cross-listed firms. The results remain robust to alternative measures of change in cash and consideration of state-owned enterprises. The AH cross-listing valuation premium for cash holdings decreases after a governance reform in the Chinese stock market. Our results suggest that AH cross-listing enhances firms’ transparency and disclosure, and thereby the value of cash holdings relative to non-cross-listed companies.

In this paper, we consider the following indirect signal generation and logarithmic sensitivity ε n t = Δ n − χ ∇ · n ∇ ln c x ∈ Ω , t > 0 c t = Δ c − c + w x ∈ Ω , t > 0 w t = Δ w − w + n x ∈ Ω , t > 0 under homogeneous Neumann boundary conditions in a ball domain Ω ⊂ R N N ≥ 4 with smooth boundary ∂ Ω . This paper considers in the singular limit ε ⟶ 0 ; the result comes from the finite time blow-up of arbitrary large values of n in the corresponding nonlocal scalar parabolic equation case when N ≥ 4 and χ > 2 N / N − 2 .

Background: Sparganosis, caused by the larval plerocercoid of Spirometra tapeworms, still poses a potential public health hazard in China. Snakes are an important source of infection for human sparganosis; however, insufficient studies on the population genetics of Spirometra isolates from snakes have occurred to date. This study collected 67 Spirometra isolates from snakes, and several definitive hosts (Panthera tigris, Prionailurus bengalensis, Felis silvestris), in 15 geographical locations in Hunan Province of central China. They were identified using a multiplex polymerase chain reaction assay. Next, these isolates’ population genetic diversity and phylogenetic pattern were explored based on mitochondrial cytb and cox1 genes. Results: All Spirometra isolates collected in the Hunan Province belonged to the genotype of the Korean “Spirometra decipiens” (KJ599679). The genetic diversity analysis based on concatenated sequences revealed no distinct genetic structure among Spirometra populations. Conclusions: The phylogenetic analysis supported the distinction between Polish and Chinese Spirometra isolates. The taxonomy of Spirometra spp. remains ambiguous; more morphological and molecular studies are necessary to clarify the systematics of the genus of Spirometra.

Amelioration of the mobility and, in particular, the thermal stability of a hole-transporting molecular semiconductor is a practicable strategy to attain the enhancement of both power conversion ef...

Clarifying the structural basis and microscopic mechanism lying behind electronic properties of molecular semiconductors is of paramount importance in further material design to enhance the performance of perovskite solar cells. In this paper, three conjugated quasilinear segments of 9,9-dimethyl-9H-fluorene, 9,9-dimethyl-2,7-diphenyl-9H-fluorene, and 2,6-diphenyldithieno[3,2-b:2',3'-d]thiophene are end-capped with two bis(4-methoxyphenyl)amino groups for structurally simple molecular semiconductors Z1, Z2, and Z3, which crystallize in the monoclinic P21/n, triclinic P1, and monoclinic C2/c space groups, respectively. The modes and energies of intermolecular noncovalent interactions in various closely packed dimers extracted from single crystals are computed based on the quantum theory of atoms in molecules and energy decomposition analysis. Transfer integrals, reorganization energies, and center-of-mass distances in these dimers as well as band structures of single crystals are also calculated to define the theoretical limit of hole transport and microscopic transport pictures. Joint X-ray diffraction and space-charge-limiting current measurements on solution-deposited films suggest the dominant role of crystallinity in thin-film hole mobility. Photoelectron spectroscopy and photoluminescence measurements show that an enhanced interfacial interaction between the perovskite and Z3 could attenuate the adverse impact of reducing the energetic driving force of hole extraction. Our comparative studies show that the molecular semiconductor Z3 with a properly aligned highest occupied molecular orbital energy level and a high thin-film mobility can be employed for efficient perovskite solar cells, achieving a good power conversion efficiency of 20.84%, which is even higher than that of 20.42% for the spiro-OMeTAD control.

Two-dimensional (2D) perovskites incorporating hydrophobic organic spacer cations show improved film stability and morphology compared to their three-dimensional (3D) counterparts. However, 2D perovskites usually exhibit low photoluminescence quantum efficiency (PLQE) owing to strong exciton-phonon interaction at room temperature, which limits their efficiency in light-emitting diodes (LEDs). Here, we demonstrate that the device performance of 2D perovskite LEDs can be significantly enhanced by doping Mn(2+)in (benzimidazolium)(2)PbI4 2D perovskite films to suppress the exciton-phonon interaction. The distorted [PbI6](4-) octahedra by Mn-doping and the rigid benzimidazolium (BIZ) ring without branched chains in the 2D perovskite structure lead to improved crystallinity and rigidity of the perovskites, resulting in suppressed phonon-exciton interaction and enhanced PLQE. On the basis of this strategy, for the first time, we report yellow electroluminescence from free excitons in 2D (n = 1) perovskites with a maximum brightness of 225 cd m(-2) and a peak EQE of 0.045%. Funding Agencies|Major Research Plan of the National Natural Science Foundation of China [91733302]; European Union [2016YFE0112000]; National Basic Research Program of China-Fundamental Studies of Perovskite Solar Cells [2015CB932200]; National Natural Science Foundation of China [61634001, 51703094]; Natural Science Foundation of Jiangsu Province, China [BK20170991, BK20150043, BK20150064]; National Science Fund for Distinguished Young Scholars [61725502]; Natural Science Fund for Colleges and Universities in Jiangsu Province of China [17KJB150023]; Synergetic Innovation Center for Organic Electronics and Information Displays

A cobalt-based redox electrolyte as a possible alternative to the traditional iodine counterpart has brought forth the remarkable power conversion efficiency (PCE) advancement in the past years of ...

Halide ion’s doping of fullerene core is crucial on the properties of highly conductive self-n-doped fullerene ammonium halides, which are a kind of promising electron transport material for photovoltaics. Herein, to understand their photoexcited electron transfer (ET) property, antimicrobial photodynamic inactivation (aPDI) activities of these materials were tested based on their unique electronic structure and bacterial electrokinesis. We observed that illuminated self-n-doped fullerene ammonium iodides (PCBANI and PCBDANI) could exhibit significant improvement of activity against two important plant pathogenic fungi, Sclerotinia sclerotiorum and Fusarium graminearum as electron donor, compared with that in dark. Through comprehensive studies, such as aPDI activity, hyphal cell morphology, ultrafast transient absorption spectroscopy, solid state nuclear magnetic resonance (ssNMR), level of total cellular reactive oxygen species (ROS), we verified that not ROS but I radical’s oxidative stress is responsible for the improved aPDI activity. Moreover, the photobiological activity of self-n-doped fullerene ammonium halides is dependent on the reducing capacity of halide anions. The ET rate from anion to an excited fullerene core decreased successively from I– to Br– and then Cl–, illustrating that the generation rate of I radical species was the fastest and consistent with the high activity of fullerene ammonium iodides. Remarkably, adding potassium iodide did not enhance PCBANI’s antifungal activity. These results disclose that the unique electronic structure of iodide and fullerene core in self-n-doped PCBANI aggregates are critical for its aPDI activity. Consequently, we propose a possible dual-redox cycles mechanism involving photoexcited fullerene radical anions and I radical species in self-n-doped fullerene ammonium iodide aggregate to exhibit sustainable aPDI activity. This work reveals that halide ions play an equally important role as fullerene core in photoexcited ET property of self-n-doped fullerene ammonium halides.

The simultaneous realization of both high-efficiency and long-term durability of transparent, colorful dye-sensitized solar cells (DSSCs) is of paramount importance to gradually supersede the aesthetically repulsive silicon solar cells for future building integrated photovoltaic (BIPV) applications. In this paper we synthesize two donor–acceptor organic dyes C296 and C298 characteristic of a polycyclic heteroaromatic unit 6,11-dihydrothieno[3′,2′:8,9]chryseno[10,11,12,1-bcdefg]carbazole (TCC) as the primary electron-releasing unit, in conjunction with the 4-(benzo[c][1,2,5]thiadiazol-4-yl)benzoic acid (BTBA) and 4-(benzo[c][1,2,5]thiadiazol-4-ylethynyl)benzoic acid (BTEBA) electron acceptors. Both dyes possess suitable energy gaps, reasonably long excited state lifetimes, and high charge separation yields, allowing for the fabrication of transparent DSSCs with over 10% power conversion efficiencies under the illumination of 100 mW cm−2, AM1.5G sunlight for the first time. The see-through DSSCs based on the TCC dye with BTEBA as the electron acceptor display good efficiency retention after full sunlight soaking at 60 °C for 1000 h.

Bone defect refers to the destruction of the structural integrity of the bone. The shapes of bone defects are different. The various three-dimensional models design methods are selected to achieve the design of repairing and reconstruction models of two kinds of bone defects. For patients with partial defects in the right tibia and fibula, a three-dimensional model is mirrored through the left leg according to the symmetry, and the defect part is obtained through the Boolean operation with the right leg. For patients with cervical fracture, the centrum is separated from the cervical vertebrae, and two cylinders are designed as screw access channels. A layer of panel is constructed on the surface. Then the separated panel is thickened to build a model of vertebral pedicle screw.

Maintaining both a high external quantum efficiency and a large open-circuit photovoltage of dye-sensitized solar cells (DSSCs) is a crucial challenge in the process of developing narrow-energy-gap dyes for the capture of infrared solar photons. Herein, we report two donor-acceptor organic dyes, C294 and C295, with a polycyclic heteroaromatic unit, 6,11-dihydrothieno[3',2':8,9]chryseno[10,11,12,1-bcdefg]carbazole (TCC), as the central module of the electron donor, and ethylbenzothiadiazole-benzioc acid as the electron acceptor. The interfacial charge recombination was successfully mitigated by introducing an additional branched aliphatic chain in C295. Furthermore, the O⋅⋅⋅S nonbonding interaction between the oxygen atom of the alkoxy group and the sulfur atom of the thiophene in C295 controlled the conformation of C295, resulting in a narrow energy-gap. Time-resolved spectroscopic measurements on C294 and the model dye C272 indicated that the elevation of the HOMO energy level decreased the kinetics and yield of hole injection owing to a reduction in the driving force and that the shortened excited-state lifetime caused by the narrowing of the energy gap was unfavorable for electron injection. By fine tuning the composition of the electrolyte, C294 and C295 eventually achieved high power conversion efficiencies of 11.5 % and 12.4 %, respectively, under full sunlight of air mass 1.5 global conditions.

In this work, the excited-state intermolecular hydrogen bonding interactions, photoinduced charge transfer, and vibrational spectroscopic properties of deprotonated deoxyadenosine monophosphate [dAMP-H]− anion in aqueous solution were investigated by the DFT/TDDFT method. The intermolecular hydrogen-bonded model complexes [dAMP-H]−–nH2O (n = 0, 1, 2, 3, 4) in both the ground state and electronic excited state were first discussed. Analysis of frontier molecular orbitals reveals an intramolecular charge transfer (ICT) state for [dAMP-H]−–nH2O (n = 0, 1, 2) complexes in which charge transfer occurs from the phosphate group to the base. However, it becomes a locally excited (LE) state for [dAMP-H]−–nH2O (n = 3, 4) complexes, which only locates on the adenine moiety. The excited energies of the first excited state of [dAMP-H]−–nH2O (n = 0, 1, 2, 3) increase gradually during the introduction of water molecules, but decreases with the fourth water molecule at adenine site. The fourth water molecule has little influence on the structure but significant to the photoexcitation. Upon electronic excitation, stretching vibration frequencies of N H and O H of hydrogen bonds: N5 H10 ⋯ O9, O9 H19 ⋯ O10 and O10 H21 ⋯ O3 are red-shifted. The excited-state bond lengths of these hydrogen bonds are also shortened. Therefore, the total intermolecular hydrogen bonding interaction at the base moiety is significantly strengthened in the electronic excited state.

Albeit the excellent hole extraction yield and conductivity, a doped molecular semiconductor film composed of the state-of-the-art spiro-OMeTAD is so far unqualified for durable perovskite solar cells at 85 °C. We herein blend a commercial polymer poly(9-vinylcarbazole) and a nonvolatile organic salt 4-(tert-butyl)pyridinium bis(trifluromethanesulfonyl)imide with spiro-OMeTAD, yielding a semiconducting composite with high conductivity and high glass transition temperature. The resultant organic composite can be solution-processed into a hole transport layer for 85 °C durable perovskite solar cells with over 21% efficiency, due to good control on charge transport resistance, interfacial recombination resistance, and hole extraction yield. Multiple experimental measurements and molecular dynamics modeling jointly unravel the crucial impact of organic coatings on the thermal decomposition of hybrid perovskites from the split-new perspective of gas diffusion modulation.

Reducing the optical energy gap of a photosensitizer to broaden the spectral response is of paramount importance to improve the power conversion efficiency of dye-sensitized solar cells (DSSCs). Herein, we report two isomeric photosensitizers with planar aromatic polycycles 7H-phenaleno[1,2-b]thiophene (PT) and 7H-benzo[6,7]indeno[1,2-b]thiophene (BIT) as the kernel units of electron-donors and 4-(benzo[c][1,2,5]thiadiazol-4-ylethynyl)benzoic acid (BTEBA) as the electron-acceptor. The efficient electron-acceptor BTEBA can bring forth an obvious downward shift of the lowest unoccupied molecular orbital energy level of an organic photosensitizer and thus shrink the energy gap significantly. Femtosecond fluorescence decay and nanosecond transient absorption measurements suggest that the two low-energy-gap photosensitizers present efficient charge separation yields in DSSCs. These two photosensitizers are used to make coadsorbate-free, high-photovoltage-output DSSCs in combination with a tris(2,2′-bipyridine)cobalt based redox electrolyte. DSSCs with the BIT based photosensitizer achieves up to 10.9% power conversion efficiency at the 100 mW cm-2, simulated AM1.5G conditions. The cell using the PT based photosensitizer presents an excellent stability under full sunlight soaking at 60 °C for 1000 h, retaining 88% of its initial efficiency.

This study aims to efficiently estimate the crop water content of winter wheat using high spatial and temporal resolution satellite-based imagery. Synthetic-aperture radar (SAR) data collected by the Sentinel-1 satellite and optical imagery from the Sentinel-2 satellite was used to create inversion models for winter wheat crop water content, respectively. In the Sentinel-1 approach, several enhanced radar indices were constructed by Sentinel-1 backscatter coefficient of imagery, and selected the one that was most sensitive to soil water content as the input parameter of a water cloud model. Finally, a water content inversion model for winter wheat crop was established. In the Sentinel-2 approach, the gray relational analysis was used for several optical vegetation indices constructed by Sentinel-2 spectral feature of imagery, and three vegetation indices were selected for multiple linear regression modeling to retrieve the wheat crop water content. 58 ground samples were utilized in modeling and verification. The water content inversion model based on Sentinel-2 optical images exhibited higher verification accuracy (R = 0.632, RMSE = 0.021 and nRMSE = 19.65%) than the inversion model based on Sentinel-1 SAR (R = 0.433, RMSE = 0.026 and nRMSE = 21.24%). This study provides a reference for estimating the water content of wheat crops using data from the Sentinel series of satellites.