In组分梯度渐变的n-i-p结构InGaN太阳能电池性能研究

为了优化InGaN太阳能电池结构并有效地指导实际电池的制备,研究了n-i-p(p层在下)In组分梯度渐变结构的InGaN太阳能电池的性能特征。通过APSYS软件模拟计算,对比采用p-i-n渐变结构(p层在上)和n-i-p渐变结构(p层在下)的InGaN太阳能电池的器件性能。结果表明,采用n-i-p渐变结构的InGaN电池,i-InGaN层在低In组分下没有明显的优势,而在高In组分下的器件性能较好。在In组分为0.62时,转换效率最高达到8.48%。分析表明,p层在下的n-i-p渐变结构使得InGaN电池的极化电场与耗尽区的内建电场方向一致,有利于载流子的输运。采用n-i-p渐变结构有利于制备高性能的InGaN太阳能电池。     

General equation describing viscosity of metallic melts under horizontal magnetic field

Viscosities of pure Ga, Ga_(80)Ni_(20), and Ga_(80)Cr_(20) metallic melts under a horizontal magnetic field were investigated by a torsional oscillation viscometer. A mathematical physical model was established to quantitatively describe the viscosity of single and binary metallic melts under a horizontal magnetic field. The relationship between the viscosity and the electrical resistivity under the horizontal magnetic field was studied, which can be described as η_B = η +(2H/πΩ)B~2(η_B is the viscosity under the horizontal magnetic field, η is the viscosity without the magnetic field, H is the height of the sample,? is the electrical resistivity, and B is the intensity of magnetic field). The viscosity under the horizontal magnetic field is proportional to the square of the intensity of the magnetic field, which is in very good agreement with the experimental results. In addition, the proportionality coefficient of ηB and quadratic B, which is related to the electrical resistivity,conforms to the law established that increasing the temperature of the completely mixed melts is accompanied by an increase of the electrical resistivity. We can predict the viscosity of metallic melts under magnetic field by measuring the electrical resistivity based on our equation, and vice versa. This discovery is important for understanding condensed-matter physics under external magnetic field.     

Steered coherence and entanglement in the Heisenberg XX chain under twisted boundary conditions

We study steered coherence(SC) and entanglement in a three-spin Heisenberg XX model under twisted boundary conditions and show that their strengths can be significantly enhanced by tuning the twist angle. The optimal twist angle θ_(opt) for achieving the maximum l_1 norm of SC is π in the region of weak field B and decreases gradually from π to 0 when B increases after a critical value, while for the relative entropy of SC, θ_(opt) equals π in the weak field region and 0 otherwise.The entanglement and the critical temperature above which the entanglement vanishes can also be significantly enhanced by tuning the twist angle from 0 to π.     

一端附壁高分子链的Monte Carlo研究

采用简立方格点上的Monte Carlo模拟,研究一端被无限大不可穿透平面壁吸附的高分子链的均方末端距<R²>,以及高分子链的质量中心到平面吸附壁的平均距离<Z>,与链长N、参数u(u=e^-ε/kT,ε是链骨架原子间的相互作用能量,k是玻耳兹曼常数,T是热力学温度)的关系。结果表明:<R²>和<Z>都服从标度律,<R²>=αN^γ,<Z>=βN^η,其中,γ、η、α、β都是u的函数;u从1减小到0.5,则γ从1.01增大到1.19,η从0.51增大到0.60.     

Mid-infrared supercontinuum and optical frequency comb generations in a multimode tellurite photonic crystal fiber

We numerically investigate the mid-infrared(MIR) supercontinuum(SC) and SC-based optical frequency comb(OFC) generations when the three optical modes(LP01, LP02, and LP12) are considered in a multimode tellurite photonic crystal fiber(MM-TPCF). The geometrical parameters of the MM-TPCF are optimized to support the multimode propagation and obtain the desired dispersion characteristics of the considered three optical modes. When the pump pulse with center wavelength λ = 2.5 μm, width T = 80 fs, and peak power P = 18 k W is coupled into the anomalous dispersion region of the LP01, LP02, and LP12 modes of the MM-TPCF, the-40-d B bandwidth of the generated MIR SCs can be up to2.56, 1.39, and 1.12 octaves, respectively, along with good coherence. Moreover, the nonlinear dynamics of the generated SCs are analyzed. Finally, the MIR SCs-based OFCs are demonstrated when a train of 50 pulses at 1-GHz repetition rate is used as the pump source and launched into the MM-TPCF.     

Control of spins in a nano-sized magnet using electric-current

With the development of spintronics,spin-transfer torque control of magnetic properties receives considerable attention.In this paper the Landau-Lifshitz-Gilbert equation including the torque term is used to investigate the magnetic moment dynamics in the free layer of the ferromagnet/non-magnetic/ferromagnet(FM1/N/FM2) structures.It is found that the reverse critical time τ_c decreases with the current increasing.The critical time τ_c as a function of current for the perpendicular and parallel easy magnetic axes are the same.The critical time τ_c increases with the damping factor α increasing.In the case of large current the influence of the damping factor α is smaller,but in the case of little torque the critical time τ_c increases greatly with the damping increasing.The direction of the magnetization in the fixed layer influences the critical time,when the angle between the magnetization and the z direction changes from 0.1π to 0.4π,the critical time τ_c decreases from 26.7 to 15.6.     

负磁剪切等离子体中离子温度梯度驱动不稳定性分析

采用打靶法,数值求解了在负磁剪切托卡马克等离子体中离子温度梯度驱动的复本征模方程.数值计算表明,环向旋转剪切流可以整体上改变剪切板η_i不稳定性.在等离子体极小q磁面附近的芯部区域,环向剪切流有稳定η_i模的作用.     

开槽扰流片流动特性研究

用标准的k-ε湍流方程结合近壁流动的两层带状模型,在非结构网格上采用SIMPLE算法,对不同开孔度的开槽扰流片流动特性进行了数值模拟,并和测压实验结果进行了比较.结果表明开槽扰流片的流动结构取决于上下两部分流场的相互耦合作用,开孔度η=50%时两个流场互相没有干扰,开孔度η=20%,30%时两个流场相互耦合作用很强,扰流片后有较大的回流区以及较小的湍流动能.     

基于动态最小生成树路由协议的数据聚融算法

大规模的地理环境监测,以及用来传输与处理数据的物理基础设施无法和监测区域的规模保持同样的增速,使得不可靠链路下的数据采集与处理呈现出一种饱和流状态,无线传感器网络的能力看似难以稳定.另一方面,尽管理想网络模型的计算结果足够精确,然而,由于与实际应用偏差甚大,使得网络用户无法充分地分析和利用从工业现场所获得到的网络感知数据,并且没有针对网络规模和性能对数据聚融的影响进行分析.为此,本文提出以"过渡区"作为工业现场仿真的假设条件,并在此基础上提出了一种面向实际应用的数据聚融算法,即基于可信度的数据聚融算法(R算法).在具体设计R算法过程中,选用聚集和操作符SUM为例,通过对网络提供出的近似聚集和加以自动分析、综合,针对相对误差界限ε,计算出近似聚集和的可信度的下限η;并将近似聚集和、参数η一同提供给用户,在为用户提供网络概要信息的同时,还提供了参数η作为对信息可信度的判断,以便指导用户对数据聚集结果进行深度处理和提高网络的感知性能.仿真实验描述了过渡区内由于信噪比导致的链路不可靠所引起的η的变化规律;讨论了网络性能和规模对η的影响,随着网络运行周期的增加和网络规模的增大,η的值将逐渐靠近0;从而为WSNs从理论模型投入实际工业应用提供了理论依据和经验公式.     

Ge-Sb-Se硫系玻璃的折射率和热光系数

Ge-Sb-Se硫系玻璃被认为是极佳的红外传输材料和有潜力的非线性光学材料.在光学设计中,玻璃的线性折射率(n)及其热光系数(ζ)是关键技术参数.以预测和调控Ge-Sb-Se玻璃的n和ζ为目的,考察了玻璃的n,ζ,密度(d)和体积膨胀系数(β)与化学参数dSe和拓扑网络结构参数r的内在联系.研究发现,玻璃的n随d的增加而增大;ζ随β的增大而近似线性减小;β随dSe的减小或r的增大而减小;当Ge含量固定时, d随dSe的减小或r的增大而增大,当Sb含量固定时, d在dSe=0时具有最小值.基于实测d和n,拟合获得了Ge, Sb和Se元素在2—12μm波段的摩尔折射度(R_i),分别为R_(Ge)=10.16—10.50 cm~3/mol,RSb=16.71—17.08 cm~3/mol和RSe=11.15—11.21 cm~3/mol,根据d和R_i计算得到的n与实测值的偏差小于1%.基于实测ζ和β,拟合得到了Ge, Sb和Se元素在2—12μm波段的摩尔折射度温度系数(φ_i),分别为φ_(Ge)=21.1—22.6 ppm/K,φ_(Sb)=7.2—8.4 ppm/K和φ_(Se)=90.2—94.2 ppm/K,根据β和φ_i计算得到的ζ与实测值的偏差小于6 ppm/K.     

Properties of strong-coupling magneto-bipolaron qubit in quantum dot under magnetic field

Based on the variational method of Pekar type, we study the energies and the wave-functions of the ground and the first-excited states of magneto-bipolaron, which is strongly coupled to the LO phonon in a parabolic potential quantum dot under an applied magnetic field, thus built up a quantum dot magneto-bipolaron qubit. The results show that the oscillation period of the probability density of the two electrons in the qubit decreases with increasing electron–phonon coupling strength α, resonant frequency of the magnetic field ω_c, confinement strength of the quantum dot ω_0, and dielectric constant ratio of the medium η; the probability density of the two electrons in the qubit oscillates periodically with increasing time t, angular coordinate φ_2, and dielectric constant ratio of the medium η; the probability of electron appearing near the center of the quantum dot is larger, and the probability of electron appearing away from the center of the quantum dot is much smaller.     

双色场诱导气体产生相干可控的四次谐波

利用钛宝石飞秒激光器输出的基频脉冲ω及其倍频脉冲2ω所构成双色场作用空气, 实验中检测到了中心波长处于真空紫外波段的四阶谐波. 在气体未发生电离的情况下, 四次谐波强度对双色场的能力依赖关系显示其产生是参量过程2ω+ω+ω→4ω的贡献. 当气体发生电离, 四次谐波强度与双色场相对相位有关, 可通过双色场相干控制. 实验研究了四次谐波对双色场相位的依赖性以及与太赫兹波的关联性, 其结果与数值模拟结果相符, 分析发现当气体发生电离时四次谐波的产生过程存在太赫兹辐射Ω_THz的参与, 是参量过程2ω+2ω±Ω_THz→4ω和2ω+ω+ω→4ω的共同贡献.     

Effects of pressure on structural,electronic, and mechanical properties of α,β,and γ uranium

The first-principles methods have been employed to calculate the structural, electronic, and mechanical properties of the α, β, and γ phases of uranium under pressure up to 100 GPa. The electronic structure has been viewed in forms of density of states and band structure. The mechanical stability of metal U in the α, β, and γ phases have been examined.The independent elastic constants, polycrystalline elastic moduli, as well as Poisson's ratio have been obtained. Upon compression, the elastic constants, elastic moduli, elastic wave velocities, and Debye temperature of α phase are enhanced pronouncedly. The value of B/G illustrates that α and γ phases are brittle in ground state.     

梯度掺杂体异质结对有机太阳能电池光电转换效率的影响

基于传统的体异质结有机太阳能电池结构, 对结构中的混合层改用梯度掺杂的方法, 在AM1.5, 100 mW/cm²光照下, 使得器件的短路电流由原来的7.72 mA/cm²提高到了9.18 mA/cm², 相应的光电转换效率提高了25%. 器件性能的提升归因于梯度掺杂体系的引入使得体异质结混合层中同一材料分子之间形成了较好的连续网络结构, 降低了器件的串联电阻, 提高了电极对载流子的收集效率, 从而提高了器件的光电转换效率. 关键词： 有机太阳能电池 体异质结 梯度掺杂     

4pi聚焦系统中振幅和相位调制的径向偏振涡旋光束聚焦特性的研究

基于Richards-Wolf矢量衍射积分公式, 研究了径向偏振涡旋光束在振幅和相位调制下的4pi聚焦特性.振幅调制是通过振幅滤波实现, 即改变入射光束起始积分值达到调节,相位调制是通过添加相位延迟角δ 的液晶相位延迟器来改变入射光束的偏振态.模拟结果显示,随着振幅的减小, 4pi聚焦系统焦点附近的光轴上呈现出多光球结构; 而相位调制对焦点附近的光强分布产生拉伸作用, 即调节入射光束的拓扑核m和相位延迟器的延迟角δ,可以得到特殊的光强分布. 随着相位δ增大, m=0产生的多光球结构慢慢向光链结构转变,最终变成暗通道;而m=1产生的光链结构慢慢变成光球结构; m=2产生的暗通道变成光球和光链叠加的结构, 这种特殊聚焦光束在光学微操纵领域具有潜在的应用价值. 关键词： 物理光学 偏振 光链 4pi聚焦系统     

硒化锑薄膜太阳电池的模拟与结构优化研究

采用wx-AMPS模拟软件对硒化锑(Sb_2Se_3)薄膜太阳电池进行建模仿真,将CdS, ZnO和Sn02的模型应用到Sb_2Se_3太阳电池的电子传输层中.结果显示,应用CdS和ZnO都能实现较高的器件性能,并发现电子传输层电子亲和势(Xe-ETL)的变化能够调节Sb_2Se_3太阳电池内部的电场分布,是影响器件性能的关键参数之一.过高或者过低的Xe-ETL都会使电池的填充因子降低,导致电池性能劣化.当Xe-ETL为4.2eV时,厚度为0.6μm的Sb_2Se_3太阳电池取得了最优的7.87%的转换效率.应用优化好的器件模型,在不考虑Sb_2Se_3层缺陷态的理想情况下,厚度为3μm的Sb_2Se_3太阳电池的转换效率可以达到16.55%(短路电流密度J_(SC)=34.88 mA/cm~2、开路电压V_(OC)=0.59 V、填充因子FF=80.40%).以上模拟结果表明,Sb_2Se_3薄膜太阳电池在简单的器件结构下就能够获得优异的光电性能,具有较高的应用潜力.     

三种胺羧配合物的113Cd NMR研究

该文对Cd-HEDTA(N-(2-羟基乙基)乙二胺-N',N',N'-三乙酸),Cd-PDTA(1,2丙二胺四乙酸)和Cd-DTPA(二乙三胺五乙酸)的¹¹³Cd NMR谱和自旋晶格弛豫时间T₁,及NOE因子进行了研究.结果表明,Cd-HEDTA和Cd-PDTA结构与Cd-EDTA类似,Cd-PDTA双线归因于其可能的两种异构体.Cd-DTPA大的化学位移表明其具有七配位的五角双锥结构.在这种结构中DTPA可用三个氮原子参加配位.对¹¹³Cd自旋晶格弛豫时间分析表明,Cd-DTPA配合物中质子偶极作用机理的贡献较大,这归因于Cd DTPA有更多的乙酸根亚甲基质子参与偶极作用.     

具有时滞反馈的非对称双稳系统中的振动共振研究

研究了具有时滞反馈的非对称双稳系统中的振动共振现象. 在绝热近似条件下, 应用快慢变量分离法得到系统响应振幅的解析表达式Q, 分析了时滞参数α和不对称参数r对振动共振现象的影响. 结果表明: 在Q-α平台上, α可以诱导响应幅值的极大值以输入高频信号和低频信号的周期出现. 不对称参数并不影响共振发生的位置, 但是能够增强响应幅值. 在Q-B (B为高频信号振幅)平台上, 共振发生的位置B_VR随着α呈现两种不同的周期关系, 且周期分别为输入高频信号和低频信号的周期. 在Q-Ω (Ω高频信号频率)平台上, 随着时滞参数的增大, 当B较小时, 在Ω的小值区间内, Q呈现出多重共振现象, 在Ω的大值区间, Q趋于定值.     

旋转方形散射体对三角晶格磁振子晶体带结构的优化

用改进的平面波展开法数值计算了正方形散射体三角排列的二维磁振子晶体当散射体旋转时的带结构. 结果显示, 同样的填充率下, 旋转正方柱散射体可以在新的频率范围内打开更多的带隙, 或者使低频带隙加宽. 说明旋转散射体可以有效地优化带隙.     

Control schemes for synchronizing two subnetworks with weak couplings

In this paper, we propose a well-designed network model with a parameter and study full and partial synchronization of the network model based on the stability analysis. The network model is composed of a star-coupled subnetwork and a globally coupled subnetwork. By analyzing the special coupling configuration, three control schemes are obtained for synchronizing the network model. Further analysis indicates that even if the inner couplings in each subnetwork are very weak, two of the control schemes are still valid. In particular, if the outer coupling weight parameter θ is larger than (n2 2n)/4, or the subnetwork size n is larger than θ2, the two subnetworks with weak inner couplings can achieve synchronization. In addition, the synchronizability is independent of the network size in case of 0 < θ < n/(n + 1). Finally, we carry out some numerical simulations to confirm the validity of the obtained control schemes. It is worth noting that the main idea of this paper also applies to any network consisting of a dense subnetwork and a sparse network.