Aqueous-processed insulating polymer/nanocrystal solar cells with effective suppression of the leakage current and carrier recombination

As one of the most environmentally friendly photovoltaic(PV) conversion equipments,aqueousprocessed CdTe nanocrystal solar cells(NC SCs) have attracted great interest in recent years because of their excellent properties such as high charge-carrier mobility and broad absorption.However,two issues including interfacial recombination and leakage current seriously restrict their performance.In this paper,insulating polymer poly(vinyl pyrrolidone)(PVP) is introduced into CdTe NC SCs to solve the problems.The experimental results of transmission electron microscopy(TEM),atomic force micro scopy(AFM) and dark current measurements,etc.,demonstrate the leakage current is effectively suppressed by introducing PVP.Through further designing device structure,the reduction of interfacial recombination after introducing PVP is confirmed.By strategically taking the advantages of PVP properties(e.g.,water solubility and thermostability),the power conversion efficiency of the devices with PVP is enhanced by almost 37% compared to pure CdTe devices.This work demonstrates an effective and low-cost method to fabricate NC SCs via aqueous route.Moreover,it also proves that appropriate content of insulating polymer is of beneficial in promoting the PV performance.     

琅琊山景区不同叶绿素条件下树种叶片光谱差异分析

叶绿素含量高低反映植物健康状况,研究景区树种叶片叶绿素绝对值(SPAD)不同的光谱变化规律能为叶绿素高光谱监测波段识别与景区树种管理提供理论支撑。从琅琊山景区灌木和乔木类选取9个常见树种,探讨相同树种叶片SPAD值变化时的光谱差异,同时,横向对比相同SPAD值不同树种叶片的光谱特征,并深入分析不同树种叶片SPAD值与单波段原始光谱、光谱倒数、一阶微分、二阶微分及波段组合差值指数、归一化指数、比值指数、一阶微分归一化指数、一阶微分比值指数之间的关系。结果表明：9个所测树种叶片随着叶绿素SPAD值的升高,光谱变化规律各不相同,在可见光波段区分明显,总体上,光谱反射率最高的样本组SPAD值较低;叶绿素SPAD值相同时,在可见光波段,桂花较其余树种反射率整体较高; 在780~1 350 nm波段,广玉兰叶片反射率始终排前三,其余波段变化规律不明显;原始光谱反射率的二阶微分与海桐叶片SPAD值相关系数最大,一阶微分与其余8种相关性最高;与灌木、落叶乔木叶片SPAD值相关系数最大的光谱指数分别为差值指数、一阶微分归一化指数,与常绿乔木、不分树种相关系数最大的为一阶微分比值指数。     

掺镁YFeO3固溶体的电导和气敏性能研究

用化学共沉淀法制备了复合氧化物ＹＦｅＯ３镁掺杂固溶体Ｙ１－ＭｇｘＦｅＯ３气敏半导体材料,并对其相组成、电导和气敏性能进行了研究。结果表明：Ｍｇ＾２＋在ＹＦｅＯ３的Ａ位固溶范围为０≤ｘ≤０．８;电导测量显示,该Ｐ型固溶材料电导突变较纯相ＹＦｅＯ３低１００℃以上;９００℃以下灼烧４ｈ所得的Ｙ０．９４Ｍｇ０．０６ＦｅＯ３粉料制作的元件在２５７℃时对乙醇灵敏度最高,对４．５μｍｏｌ／Ｌ乙醇的灵敏度高达４４     

Novel solid solutions of Ca3–1.5xYbx□0.5xB2SiO8: Synthesis,crystal structure,luminescence and thermal properties

New cation-deficient solid solutions of Ca_3–1.5xYb_x□_0.5xB₂SiO₈ (x = 0–0.4) based on Ca₃B₂SiO₈ borosilicate were synthesized. It was found that solid solutions in the range 0 ≤ x < 0.125 are structurally similar to the low-temperature monoclinic β-Ca₃B₂SiO₈, whereas those of the range 0.187 < x < 0.4 are similar to the high-temperature orthorhombic α-Ca₃B₂SiO₈. The crystal structures of solid solutions with x = 0.2 and 0.3 were determined from single crystal X-ray diffraction data and refined in the orthorhombic space group Pnma to R_obs = 0.051 and 0.057, respectively. Thermal expansion of the samples with x = 0.1, 0.3 was investigated using powder high-temperature X-ray diffraction in the temperature range of 20–800 °C. Photoluminescence spectra of Ca_3–1.5xYb_x□_0.5xB₂SiO₈ consist of the intra-configurational ²F_5/2–²F_7/2 transitions inside of Yb³⁺ ions with a maximum at 975 nm.     

The effect of high external pressures on the infrared and Raman spectra of crystalline tetra-n-propylammonium bromide

The infrared and Raman spectra of crystalline tetra-n-propylammonium bromide, (n-C₃H₇)₄NBr, have been measured in the 3000 – 700 cm⁻¹ region and vibrational assignments are proposed in part on the basis of the known crystal structure. Pressure-tuning infrared and Raman studies of this material were also undertaken using a diamond-anvil cell. There is a pressure-induced phase transition occurring between 1.8 and 2.1 GPa, which is most likely a second-order transition. Some differences are noted between the infrared data reported here and those given in an earlier high-pressure infrared study. The spectroscopic results will be useful in examining zeolites involving (n-C₃H₇)₄NBr as a template.     

图的{P4}——分解

一个图G的路分解是指一路集合使得G的每条边恰好出现在其中一条路上．记Pl长度为l-1的路，如果G能够分解成若干个Pl，则称G存在{Pl}——分解，关于图的给定长路分解问题主要结果有：（i）连通图G存在{P3}-分解当且仅当G有偶数条边（见[1]）；（ii）连通图G存在{P3，P4}-分解当且仅当G不是C3和奇树，这里C3的长度为3的圈而奇树是所有顶点皆度数为奇数的树（见[3]）．本文讨论了3正则图的{P4}--分解情况，并构造证明了边数为3k（k∈Z且k≥2）的完全图Kn和完全二部图Kr,s存在{P4}-分解.     

On minimally 2-(edge)-connected graphs with extremal spectral radius

A graph is minimally 2-(edge)-connected if it is 2-(edge)-connected and deleting any arbitrary chosen edge always leaves a graph which is not 2-(edge)-connected. In this paper, we completely characterize the minimally 2-(edge)-connected graphs having the largest and the smallest spectral radius, respectively.     

Hydrothermal synthesis and the enhanced blue upconversion luminescence of NaYF4:Nd3+,Tm3+,Yb3+

Nd³⁺, Tm³⁺ and Yb³⁺ co-doped NaYF₄ upconversion (UC) material was synthesized by the hydrothermal method. The structure of the sample was characterized by the X-ray diffraction, and its UC luminescence properties were investigated in detail. Under the 980 nm semiconductor laser excitation, its UC spectra exhibited distinct emission peaks at 451 nm, 475 nm and 646 nm respectively. On the basis of the comparison of UC spectra between NaYF₄:Nd³⁺,Tm³⁺,Yb³⁺ and NaYF₄:Tm³⁺,Yb³⁺, it was indicated that the existence of Nd³⁺ ion enhanced the blue emission intensity. The law of luminescence intensity versus pump power proved that the blue emission at 475 nm, and the red emission at 646 nm were the two-photon processes, while the blue emission at 451 nm was a three-photon process.     

A two-step explicit P-stable method of high phase-lag order for linear periodic IVPs

In this paper, we present a nonlinear two-step explicit P-stable method of fourth algebraic order and 12th phase-lag order for solving one-dimensional second-order linear periodic initial value problems (IVPs) of ordinary differential equations. Based on a special vector arithmetic with respect to an analytic function, the method can be extended to be vector-applicable for multi-dimensional problems directly. Some numerical results are reported to illustrate the efficiency of the method.     

A solvothermal route to size- and shape-controlled CdSe and CdTe nanocrystals

The size- and shape-controlled CdSe and CdTe nanocrystals, which exhibit obvious quantum confinement effect, have been synthesized by a solvothermal route. It is found that initial precursor concentrations are key factors in controlling the shape of the resulting nanocrystals. Moreover, the obtained nanocrystals are all of zinc blende structure, regardless of their sizes and shapes. A possible mechanism for the formation and growth of the nanocrystals is put forward. It is inferred that the adhesion and subsequent recrystallization of nanocrystals with an assistance of remaining monomers should be a major reason for formation and growth of the elongated nanocrystals.