N-methyl-2-pyrrolidone Iodide as Functional Precursor Additive for Record Efficiency 2D Ruddlesden-Popper (PEA)2(Cs)n−1PbnI3n+1 Solar Cells

2D perovskite (PEA)₂(Cs)_n−1Pb_nI_3n+1 (PEA: phenylethylammonium) exhibits more strengthened phase stability than its 3D components under ambient conditions and hence gained great attention in recent years. However, uncontrollable crystallization kinetics in (PEA)₂(Cs)_n−1Pb_nI_3n+1 leads to difficulty in controlling film morphology and phase-orientation regulation, resulting in poor power conversion efficiency (PCE). Herein, by incorporating precursor additive N-methyl-2-pyrrolidone iodide (NMPI), the crystallization rate during the deposition of (PEA)₂(Cs)_n−1Pb_nI_3n+1 film is efficiently regulated. As a result, the 2D or quasi-2D perovskite solar cell (PSC) delivers record PCEs in all reported 2D or quasi-2D CsPbX₃ families, for instance, the quasi-2D (n = 20) CsPbI₃ PSC exhibits a record PCE of 14.59%, showing significantly enhanced stability. Detailed characterization reveals that the NMPI forms hydrogen bonds with dimethylammonium iodide (DMAI) in the precursor to control crystallization rate for a smooth morphology with small fluctuation, which leads to improved carrier lifetime and reduced trap-density. More importantly, femtosecond transient absorption (fs-TA) measurements confirm an improved phase purity and the suppressed nonradiative recombination in quasi-2D perovskite film. It is believed that this simple additive strategy paves a new route for solving phase transition and crystallization kinetic problems in 2D and quasi-2D CsPbX₃.     

Si(001)-(2×1)的金属性表面态

利用角分辨紫外光电子谱仪,首次发现在 Si(001)-(2×1)面上存在着金属性表面态,该态位于能量为～0.1eV(E_F以下)Γ对称点附近,而且存在范围很窄.在(001)的邻面上未发现这种态.我们认为Si(001)面的金属性表面态可能来自表面部分的对称双聚键.     

自动张量低能电子衍射对GaAs(-1-1-1)-(2×2)表面结构的研究

本文通过对ＧａＡｓ（１１１）－（２×２）表面低能电子衍射（ＬＥＥＤ）Ｉ－Ｖ曲线的分析，首次定量地给出了该表面的复杂结构．结构的主要特征是Ａｓ三聚体单元吸附在表面Ｔ４位置并与下面的Ａｓ原子相键接，且表面存在较大的表面弛豫．对１０个非等价衍射束理论和实验强度曲线之间的比较得到很好的结果．     

The chemisorption of Mg on the Si(100)-(2×1) surface

正The adsorption of a half monolayer of Mg atoms on the Si(100)-(2×1) surface is studied by using the self-consistent tight binding linear muffin-tin orbital method.Energies of the adsorption systems of Mg atoms on the different sites are calculated.It has been found that the adsorbed Mg atoms are more favorable on the cave site above the surface than any other sites on the Si(100)-(2×1) surface and a metastable shallow site also exists above the surface.This is in agreement with the experimental results.The charge transfer and the layer projected density of states are also studied.     

H_2O在Si(100)-(2×1)表面上的吸附和氧化

利用AES以及HeI(21.2eV)和同步辐射(138.5eV)光电子谱研究了H_2O在Si(100)-(2 ×1)表面上的室温吸附、高温退火效应以及开始氧化的过程.AES的测量结果表明,H_2O在这种表面上的粘附系数很大,在350K下,当曝汽量约为2L时就达到饱和,其覆盖率θ=1/2.价带区域的光电子谱出现三个由于H_2O吸附而引起的特征峰,低于价带顶分别为6.2、7.2和11.5eV.350K下的 H_2O吸附导致Si 2p能级的结合能增加0.8±0.1eV,相当于一个Si原子同一个氧原子键合的情况.在 640K下退火后,出现Si 2p的第二个化学位移峰,其位置比体内Si 2p 峰约低 1.8eV,表明这时的 H_2O已经完全离解,一部分Si原子同两个氧原子键合(可能是桥键方式). 在 870K下退火,得到Si 2p的四个化学位移峰,说明氧已经贯穿进Si的体内,形成SiO_x(x=1、2、3和4).当退火温度进一步提高到T(?)970K时,恢复Si的清洁表面,表明氧被完全脱附.     

GaP(-1-1-1)-1×1表面的Ga3d化学位移

单色的 Hellα(hv=40.8eV)光电子发射测量发现:在IBA的 GaP(III)-1×1表面上,最外层Ga原子的3d能级结合能比体内减小0.75±0.05eV.解释为表面原子的极化程度低于体内.     

Si(111)-(3~(1/2)×3~(1/2))R30°-Ga表面原子结构

利用自动张量低能电子衍射 (ATL EED)定量地研究 Si(111) - (3× 3) R30°- Ga重构表面的原子结构 .证实了 Ga原子吸附在 T4位即第二层 Si原子所对的空位上 ,同时给出了表面最顶层 7个原子层的详细坐标 .可靠性因子 RVHT=0 .143表明理论计算和实验符合得非常好 .     

应变层超晶格(ZnSe)_(2n)/(ZnS_xSe_(1-x))_(2n)的电子结构

本文用LCAO-Recursion方法研究了应变层超晶格(ZnSe)_(2n)/(ZnS_xSe_(1-x))_(2n)(n=1)的电子结构。计算了两种应变组态(赝晶生长,Free-Standing生长)下超晶格总的态密度,各原子的局域和分波态密度。我们发现:带隙E_g、费米能级E_f和原子价随应变的变化而变化;(ZnSe)_(2n)/(ZnS_xSe_(1-x))_(2n)超晶格中离子键和共价键共存;电子在界面附近发生了转移。     

(Si)_(2n)/(Si_(1-x)Ge_x)_(2n)(100)形变层超晶格的电子结构

本文采用经验LCAO紧束缚方法,对晶格失配的Si和Ge所形成(Si)_(?)/(Si_(1-x)Ge_x)_(?)(100)(n=1～10)形变层超晶格进行了电子结构的计算。在计入晶格常数的变化对第一近邻相互作用的影响后,给出了超晶格能隙和导带底位置随层数的变化,讨论了能带折迭和能带边不连续对Si/Ge能隙直接间接性的影响。根据形变引起的Si和Ge导带底的反转,说明了Si层中二维电子气的现象。形变后的能带,与可得到的实验和其它理论的结果比较符合。本文还计算讨论了有效质量和界面态的问题。     

Design of a 1 × 2 novel optical switch based on polarization converters and splitters

In this paper, a 1?×?2 optical switch based on two TE/TM polarization converters, one 1?×?2-polarization beam splitter and a hybrid 2?×?2-polarization beam splitter/combiner is designed and discussed. The novelty of this work resides in the design of a 2?×?2-hybrid polarization beam combiner/splitter, operating as a 2?×?2 polarization optical switch through the combining and the splitting of polarized signals issued from two TE/TM polarization controllers. The novel hybrid splitter/combiner can route an optical signal either to a bar or a cross port with an extinction ratio higher than 90 dB, thanks to the feature of polarization splitting used in this device to suppress undesired polarization states and minimize the polarization-dependent loss. We have used polarization beam converters to switch between two orthogonal modes in order to facilitate the routing of these signals through the 2?×?2-hybrid polarization splitter/combiner. We changed the polarization states of signals, in our simulation via OptiSystem, through polarization controllers, by modifying only their phase shifts between 0 rad and π rad. The proposed 1?×?2 optical switch presents an average insertion loss of 3.5 dB.

     

Reconstruction transition (4×2) → (2×4) on the (001) surfaces of InAs and GaAs

Phase transitions involving various atomic configurations on the (001) surfaces of GaAs and InAs were studied by RHEED. A kinetic scheme of the interaction between the As₄ flow and the surface is proposed and the main equations describing the transitions are modified so as to correspond to the As₄ (rather than As₂) flux. A model of the (4×2) → (2×4) transition is suggested for reconstruction of a layer of metal atoms with subsequent stabilization by the adsorption of arsenic atoms. A considerable difference of the surface transitions in GaAs from that in InAs consists in greater force constants (more rigid bonds) in the former case. A significant role in the continuous evolution from (2×4)β to (4×2) phase in GaAs belongs to metastable disordered phases.     

First-principles investigation of the optical properties of CuIn(SxSe1–x)2

We optimized the lattice structure of sulfur-doped CuInSe₂ using first principles. The lattice constants for CuIn(S_xSe_1–x)₂ vary linearly with x according to a(x)=–0.02828x+0.58786 nm and c(x)=–0.05692x+1.1834 nm, which agree well with experimental data. The optical properties of CuIn(S_xSe_1–x)₂ were then systematically investigated using first-principles calculations with the HSE06 functional. We present data for the complex dielectric function, refractive index, extinction coefficient, reflectivity index, absorption coefficient, and optical bandgap for CuIn(S_xSe_1–x)₂. The optical bandgap E_g obtained from the absorption coefficient is 1.07 eV for CuInSe₂ and 1.384 eV for CuInS₂. These values are very close to experimental results, indicating that first-principles calculations can yield accurate bandgap values. The optical bandgap of CuIn(S_xSe_1–x)₂ increases linearly with the sulfur concentration according to E_g=0.3139x+1.0825 eV.     

自动张量低能电子衍射对GaAs()-(2×2)表面结构的研究

本文通过对ＧａＡｓ（１１１）－（２×２）表面低能电子衍射（ＬＥＥＤ）Ｉ－Ｖ曲线的分析，首次定量地给出了该表面的复杂结构．结构的主要特征是Ａｓ三聚体单元吸附在表面Ｔ４位置并与下面的Ａｓ原子相键接，且表面存在较大的表面弛豫．对１０个非等价衍射束理论和实验强度曲线之间的比较得到很好的结果．     

高探测率(>1×10~(10)cmHz~(1/2)W~(-1))InAsSb应变层超晶格红外光伏探测器

利用InAs_(0.15)Sb_(0.85)/InSb应变层超晶格(SLS)制造了一种高探测率的红外光电二极管。经表面钝化的器件在波长小于等于10μm时探测率大于等于1×10~(10)cmHz~(1/2)W~(-1)。这种器件证明了在InAsSb应变层超晶格基础上制造长波红外光伏探测器的可行性。     

Photoelectrochemical cells based on ternary compounds CuIn2n + 1Se3n + 2 (n = 3–6)

Semiconductors - Single crystals of ternary CuIn2n + 1Se3n + 2 semiconductors with the composition index n = 3, 5, 6 were grown for the first time using the direct crystallization method. It was...     

Comments on “Extend orthogonal Latin square codes for 32-bit data protection in memory applications” Microelectron. Reliab. 63, 278–283 (2016)

Additional extended orthogonal Latin square codes to protect 32-bit data words are presented. The new codes require less parity bits than the ones presented in the original paper at the cost of a moderate overhead in encoding and decoding complexity.     

高功率全光纤(2+1)×1侧面抽运合束器的研制

基于拉锥-熔合法研制了一种高功率全光纤(2+1)×1侧面抽运合束器。利用仿真软件建立理论模型,计算了合束器耦合效率,并制备出这种侧面抽运合束器。经测试,该合束器在抽运功率为600 W时,两抽运臂的耦合效率分别为98.2%和96.3%,信号光插入损耗约为0.11dB。利用该合束器搭建了千瓦级光纤激光放大器,双向抽运光功率达到1.8kW时,在1080nm处获得的激光输出功率为1.426kW。     

Poly(2,2’-(2,5-difluoro-1,4-phenylene)dithiophene-alt-naphthalene diimide) synthesized by direct (hetero)arylation reaction for all-polymer solar cells

The weak donor-strong acceptor polymer acceptors for all-polymer solar cells (all-PSCs) have gained much less attention compared with the typical donor-strong acceptor counterparts. Direct (hetero)arylation polymerization reaction is a rising synthetic method, although most of the naphthalene diimide polymer photovoltaic acceptors have been prepared by classic Stille polymerization. A weak donor-strong acceptor polymer acceptor PNB2F has been successfully designed and synthesized by the two-step direct (hetero)arylation reaction and further applied in all-PSCs. The all-PSC device based on PNB2F and electron-donating polymer PBDB-T gained a PCE of 4.49%. The results demonstrate that direct (hetero)arylation reaction is a promising tool for building efficient polymer acceptors with convenient and low-cost synthesis ideas.     

Si(331)-6×2表面相及其氧吸附特性

利用LEED、UPS和AES研究了Si(331)表面的原子再构和氧吸附特性.发现经Xe离子溅射和～800℃退火后出现Si(331)-6 ×2表面相.在～80℃下,氧在这种表面上的吸附量与曝氧量关系曲线出现两个代表不同吸附过程的斜率.提出可能的吸附模型:当1ML 氧吸附时,在每个Si(331)面元胞中,一个氧原子被吸附在第一和第二层Si原子之间的桥位上,另一个氧原子被吸附在顶位上.