Extending the π-Conjugated System in Spiro-Type Hole Transport Material Enhances the Efficiency and Stability of Perovskite Solar Modules

Hole transport materials (HTMs) are a key component of perovskite solar cells (PSCs). The small molecular 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl)-amine-9,9′-spirobifluorene (spiro-OMeTAD, termed “Spiro”) is the most successful HTM used in PSCs, but its versatility is imperfect. To improve its performance, we developed a novel spiro-type HTM (termed “DP”) by substituting four anisole units on Spiro with 4-methoxybiphenyl moieties. By extending the π-conjugation of Spiro in this way, the HOMO level of the HTM matches well with the perovskite valence band, enhancing hole mobility and increasing the glass transition temperature. DP-based PSC achieves high power conversion efficiencies (PCEs) of 25.24 % for small-area (0.06 cm²) devices and 21.86 % for modules (designated area of 27.56 cm²), along with the certified efficiency of 21.78 % on a designated area of 27.86 cm². The encapsulated DP-based devices maintain 95.1 % of the initial performance under ISOS-L-1 conditions after 2560 hours and 87 % at the ISOS-L-3 conditions over 600 hours.     

Graded central polynomials for the algebra <Emphasis Type="Italic">M</Emphasis><Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>(<Emphasis Type="Italic">K</Emphasis>)

Let M _n (K) be the algebra of all n × n matrices over an infinite field K. This algebra has a natural ℤ _n -grading and a natural ℤ-grading. Finite bases for its ℤ _n -graded identities and for its ℤ-graded identities are known. In this paper we describe finite generating sets for the ℤ _n -graded and for the ℤ-graded central polynomials for M _n (K) Partially supported by CNPq 620025/2006-9     

A research note on design of fair surfaces over irregular domains using data-dependent triangulation

Design of fair surfaces over irregular domain is a fundamental problem in computer aided geometric design (CAGD), and has applications in engineering sciences (i.e. aircraft science, automobile science and ship science etc.). In design of fair surfaces over irregular domain defined over scattered data it was widely accepted till recently that one should use Delaunay triangulation because of its global optimum property. However, in recent times it has been shown that for continuous piecewise polynomial parametric surfaces improvements in the quality of fit can be achieved if the triangulation pattern is made dependent upon some topological property of the data set or is simply data dependent. The smoothness and fairness of surface’s planar cuts is important because not only it ensures favorable hydrodynamic drag, but also helps in reducing manhours during the production of the surface. In this paper we discuss a method for construction of C¹ piecewise polynomial parametric fair surfaces which interpolate prescribed R³${\mathfrak{R}}^3$ scattered data using spaces of parametric splines defined on R³${\mathfrak{R}}^3$ triangulation. We show that our method is more specific to the cases when the projection on 2-D plane may consist of triangles of zero area. The proposed method is fast, numerically stable and robust, and computationally inexpensive. In the present work numerical examples dealing with surfaces approximated on standard curved plates, and ship hull surface have been presented.     

Geometric dual formulation for first-derivative-based univariate cubic <Emphasis Type="Italic">L</Emphasis><Subscript>1</Subscript> splines

With the objective of generating “shape-preserving” smooth interpolating curves that represent data with abrupt changes in magnitude and/or knot spacing, we study a class of first-derivative-based -smooth univariate cubic L ₁ splines. An L ₁ spline minimizes the L ₁ norm of the difference between the first-order derivative of the spline and the local divided difference of the data. Calculating the coefficients of an L ₁ spline is a nonsmooth non-linear convex program. Via Fenchel’s conjugate transformation, the geometric dual program is a smooth convex program with a linear objective function and convex cubic constraints. The dual-to-primal transformation is accomplished by solving a linear program.     

Nonaqueous synthesis and characterization of capped α-Fe2O3 nanoparticles from iron(III) hydroxy-oleate precursor

The synthesis of capped α-Fe₂O₃ nanoparticles from thermal treatment of iron (III) hydroxy-oleate in boiling organic solvents around 250 °C with retention of the integrity of the oleate units during the reaction process is reported. The formation of capped iron oxide particles is accomplished under aerobic conditions while the solvents used in the synthesis have strong influence on the nature and morphology of nanoparticles. These nanoparticles are studied by means of X-ray powder diffraction, IR and XPS while the morphology and particle size of nanocrystals are evaluated using SEM and TEM analysis suggesting the formation of monocrystalline α-Fe₂O₃ particles having cubical and spherical morphologies with sizes ranging from 20 to 30 nm. This organophilic material with oleate capping around the surfaces can be readily dispersed in organic solvents thus forming organosols. These organosols exhibit band-edge emission photoluminescence band both in toluene as well as in solid state while FT-IR analysis reveals formation oleate capped nanoparticles The XPS data indicate ferric state having doublet from Fe 2p_3/2 and Fe 2p_1/2 core-level electrons.     

利用水热合成方法制备正交氮化硼微晶

利用水热方法制备了正交氮化硼微晶, 于400 ℃时制备的氮化硼结晶质量较高, 主要物相为正交氮化硼(oBN). 在反应原料中加入水合肼和氯化铵都有利于样品结晶质量的改善和产率的提高. 在合成氮化硼反应过程中, 适当减慢反应体系的升温速率有利于提高oBN的结晶质量和产率, 但是当升温速率过慢时, oBN的稳定性有所降低, 立方氮化硼(cBN)的稳定性则在一定程度上得到提高. 此外, 反应过程中的原料配比对样品的物相及其结晶质量也有很大影响.     

Optimising cell temperature and dispersion field strength for the screening for putrescine and cadaverine with thermal desorption-gas chromatography-differential mobility spectrometry

Biogenic amines, and putrescine and cadaverine in particular, have significant importance in the area of food quality monitoring, and are also potentially important markers of infection, for cancer, diabetes, arthritis and cystic fibrosis. A thermal desorption-gas chromatograph-heated differential mobility spectrometer was constructed and the significant effect of interactions between cell temperature and dispersion field strength on the observed responses studied. The experiment design was a Box-Wilson central composite design (CCD) over the levels of 10-24 kV cm⁻¹ for dispersion field strength and 100-130 °C for cell temperature. The optimum values were estimated to be 16.22 kV cm⁻¹ and 116 °C for putrescine and 14.78 kV cm⁻¹ and 112 °C for cadaverine, respectively with an ammonia dopant at 19 mg m⁻³.An amine test atmosphere generator was constructed and produced stable concentrations of putrescine (7 mg m⁻³) and cadaverine (4 mg m⁻³) vapours at 50 ± 0.5 °C. Tenax TA-Carbotrap adsorbent tubes were used to sample putrescine and cadaverine vapour standards and a linear response function over the range of sample masses 5-20 ng was obtained at 15.0 kV cm⁻¹ 115 °C, with a R² of 0.99 for both putrescine and cadaverine. The sample mass at the limit of detection was estimated to be 3 ng for putrescine and cadaverine. Preliminary data from sampling the headspace of chicken meat revealed a 62% increase in the recovered masses of putrescine from 0.84 to 1.36 ng in the sampled air.     

System eigenmobilities in zone electrophoresis: A general moving-boundary approach

System zones in capillary zone electrophoresis represent an important topic, very interesting from the theoretical point but also important for practice. This paper is aimed at contributing to the understanding of system zones as one of the very fundamental properties of electrophoretic systems, by developing an alternative approach to the so far used vector-matrix model of calculation of system mobilities (system eigenmobilities). The presented model is based on the solution of the differential form of the moving-boundary equation. The result for acid-base systems is a single algebraic equation valid universally for a zone comprising any number of constituents (mono- or polyhydric strong or weak acids or bases and/or amphoteric compounds). The value of the described solution against previous models consists in its explicit form, expressing the system eigenmobility of a homogeneous zone of given composition as a function of only known quantities. The obtained equation is shown to be the common source of various simplified equations obtained in the past for particular simple systems. The applicability of the simplified equations is discussed in terms of completeness of the results (number of output system eigenmobilities). For non-buffered systems, the occurrence of a previously unreported non-zero value of system eigenmobility is discussed that is equal to the arithmetic average of mobilities of the solvent ions.     

A general central limit theorem for strong mixing sequences

A central limit theorem for strong mixing sequences is given that applies to both non-stationary sequences and triangular array settings. The result improves on an earlier central limit theorem for this type of dependence given by Politis, Romano and Wolf in 1997.