正电子冲击下氦电离三重微分截面的理论计算

我们发展了一种正电子碰撞原子电离的畸变波Born近似方法, 在这个方法中,正负电子偶素通道通过一个ab initio的光学势附加到入射粒子和靶的相互作用势上,且通道对电离作用被第一次被考虑在正电子碰撞原子电离的过程中. 应用这个方法计算了在50 eV入射能量范围氦的电离的三重微分截面,计算结果和实验数据很好的符合.     

Structure prediction,electronic, and mechanical properties of alkali metal MB_(12)(=Be,Mg, Ca,Sr) from first principles

Using the particle swarm optimization algorithm on structural search methods, we focus our crystal structures search on boron-rich alkali metal compounds of MB₁₂(M = Be, Mg, Ca, Sr) with simulation cell sizes of 1–2 formula units(f.u.)at 0 GPa. The structure, electronic, and mechanical properties of MB₁₂ are obtained from the density functional theory using the plane-wave pseudopotential method within the generalized gradient approximations. The formation enthalpies of MB₁₂ regarding to solid metal M and solid alpha-boron suggested the predicted structures can be synthesized except for BeB12. The calculated band structures show MB₁₂(M = Be, Mg, Ca, Sr) are all indirect semiconductors. All the calculated elastic constants of MB₁₂ satisfy the the mechanical stable conditions. The mechanical parameters(i.e., bulk modulus,shear modulus, and Young’s modulus) are derived using the Voigt–Reuss–Hill method. The G/B ratios indicated that the MB₁₂ should exhibit brittle behavior. In addition, the hardness, Debye temperature, universal anisotropic index, and the percentage of anisotropy in compression and shear are also discussed in detail. We hope our results can inspire further experimental study on these boron-rich alkali-metal compounds.     

基于MoO3/ZnO无机电荷产生层的量子点电致发光器件

氧化锌（ZnO）作为一种优异的电子传输材料,广泛应用于高性能量子点电致发光器件（QLED）中。然而,由于ZnO层较高的电荷传输速率,导致器件中过多的电子注入,使得器件内部的载流子不平衡,降低了器件的效率。此外,ZnO的易潮解性质使得其与电极之间的接触容易受到外界环境（水分和氧气）影响,从而影响器件的存储稳定性,这在倒置结构的QLED中尤为明显。为解决上述问题,我们利用MoO₃/ZnO作为电荷产生层（CGL）来制备倒置结构的QLED。这一结构改善了器件的载流子不平衡问题,使得器件的最大电流效率从12.8cd/A提升到了15.7cd/A。此外,CGL无需有电极注入电荷,而是通过电场的作用产生电荷,注入到发光层中,这降低了电极界面对器件性能的影响,从而大大提高了器件的稳定性。     

Resonance phenomena and threshold features in positron—helium scattering

Investigations of resonances and threshold behaviors in positron-helium scattering have been made using the momentum-space coupled-channels optical method.The positronium formation channels are considered via an equivalent-local complex potential.The s-wave resonances and the Wigner cusp feature at the positronium(n = 1) formation threshold are compared with the previous reports.The p-and the d-wave resonances and a Wigner cusp feature at the positronium(n = 2) formation threshold are reported for the first time.     

Coupled-channels optical calculation of positron-hydrogen resonances

An application of the coupled-channels optical method is given for the energy-dependent phenomena of positron-hydrogen resonances below the n=2 excitation threshold.The equivalent local optical potential is used to account for the target polarization and positronium formation.The calculation includes 9 explicitly physical coupled channels.The lowest S-wave resonance energy position and new resonances are found.Angular dependence of the cross section in the resonance region are investigated.     

Electron Impact Ionization Cross Section of Nitrogen Atoms

The direct ionization cross sections for electron scattering by nitrogen are calculated by applying an equivalentlocal optical model from 15eV to 1100eV. The present results are compared with the experimental data and other theoretical calculation results.     

超低效率滚降顶发射白光有机电致发光器件

利用Ag/tris-（8-hydroxyquinoline） aluminum（Alq₃）/Ag/Alq₃/Ag这一金属/有机半导体多层结构作为阳极,实现了超低效率滚降的顶发射白光器件。在该器件中,我们在蓝光和橙光发光单元之间引入一个薄的4,4′-bis（9-carbazolyl）-2,2′-biphenyl（CBP）层,从而减少橙光发光层与蓝光发光层的Dexter能量传递,用以改善白光器件发光光谱及效率。通过优化微腔设计,实现了对橙光磷光材料发射的调控。最终,我们获得了在60 000 cd/m²亮度下效率滚降仅为17%的顶发射白光器件。在效率方面,虽然顶发射白光器件与底发射白光器件不相上下,但由于微腔效应的存在,顶发射白光器件的效率滚降却远低于底发射白光器件的效率滚降。