Influence of deposition pressure on p-type a-Si:H window layer doped by trimethylboron for a-Si:H superstrate solar cell in plasma enhanced chemical vapor deposition

Wide bandgap (E_g) p-type window layer is very important for silicon based thin film solar cell to obtain high performance, especially high open-circuit voltage (V_OC). In this work, the influence of the deposition pressure on the properties of p-type a-Si:H window layer doped by trimethylboron (TMB) in plasma enhanced chemical vapor deposition (PECVD) was investigated systematically by transmission, Raman, and Fourier transform infrared (FTIR) spectroscopies. As a result, high performance hydrogenated amorphous silicon (a-Si:H) p–i–n superstrate solar cell with V_OC up to 927 mV was successfully achieved on Asahi Type-U SnO₂:F coated glass. In this case, excellent wide bandgap p-type a-Si:H window layer was fabricated under a mild deposition condition, including a low hydrogen dilution ratio (H₂/SiH₄) of 20, a relatively high deposition temperature of 220 °C, which was also adopted for the i-layer and n-layer deposition, and a moderate deposition pressure of about 160 Pa. We think it is the compromise between wide E_g and good microstructure quality of the p-layer that brings about the good solar cell performance. Such p-type window layer will be very helpful for the fabrication of a-Si:H solar cell, especially of the cell finished in a single PECVD chamber, due to its mild deposition condition.     

Printing 2D Conjugated Polymer Monolayers and Their Distinct Electronic Properties

Recently, 2D monolayer films of conjugated polymers have gained increasing attention owing to the preeminence of 2D inorganic films that exhibit unique optoelectronic and mechanical properties compared to their bulk analogs. Despite numerous efforts, crystallization of semiconducting polymers into highly ordered 2D monolayer films still remains challenging. Herein, a dynamic‐template‐assisted meniscus‐guided coating is utilized to fabricate continuous, highly ordered 2D monolayer films of conjugated polymers over a centimeter scale with enhanced backbone π–π stacking. In contrast, monolayer films printed on solid substrates confer upon the 1D fiber networks strong alkyl side‐chain stacking at the expense of backbone packing. From single‐layers to multilayers, the polymer π‐stacks change from edge‐on to bimodal orientation as the film thickness reaches ≈20 nm. Spectroscopic and cyclic voltammetry analysis reveals an abrupt increase in J‐aggregation and absorption coefficient and a decrease in bandgap and highest occupied molecular orbital level until critical thickness, possibly arising from the straightened polymer backbone. This is corroborated by an abrupt increase in hole mobility with film thickness, reaching a maximum of 0.7 cm² V^?1 s^?1 near the critical thickness. Finally, fabrication of chemical sensors incorporating polymer films of various thicknesses is demonstrated, and an ultrahigh sensitivity of the ≈7 nm thick ultrathin film (bilayers) to 1 ppb ammonia is shown.     

Texturization of mono-crystalline silicon solar cells in TMAH without the addition of surfactant

Texturization of mono-crystalline silicon solar cell by chemical anisotropic etching is still a key issue due to metal ions contamination and consumption of large amount of isopropyl alcohol (IPA) in a conventional mixture of potassium hydroxide (KOH) or sodium hydroxide (NaOH) and IPA. In this study, etching was performed on (100) silicon wafers using silicon-dissolved tetramethylammonium hydroxide (TMAH) solutions without addition of surfactant. Experiments were carried out in different TMAH concentration solutions at different temperatures for different etching time. The surface phenomena, etching rates, surface morphology and surface reflectance have been analyzed. Experimental results show that the resulted surface covered with uniform pyramids can be realized due to small changes of etching rates during the etching process. The etching mechanism has been explained basing on the experimental results and the theoretical considerations. It was suggested that all the components in the TMAH solutions play important roles in the etching process. Moreover, TMA+ ions may increase the wettability of the textured surface. A good textured surface can be obtained on conditions that the absorption of OH- /H2O is equilibrium with that of TMA+/SiO2(OH)22-.     

Direct Conversion of Fe2O3 to 3D Nanofibrillar PEDOT Microsupercapacitors

Microsupercapacitors (µSCs) are attractive electrochemical energy storage devices serving as alternatives to batteries in miniaturized portable electronics owing to high‐power density and extended cycling stability. Current state‐of‐the‐art microfabrication strategies are limited by costly steps producing materials with structural defects that lead to low energy density. This paper introduces an electrode engineering platform that combines conventional microfabrication and polymerization from the vapor phase producing 3D µSCs of the conducting polymer poly(3,4‐ethylenedioxythiophene) (PEDOT). A sputtered Fe₂O₃ precursor layer enables deposition of a 250 nm thick polymer coating comprised of a high packing density of vertically aligned PEDOT nanofibers possessing exceptional electrical conductivity (3580 S cm^?1). The 3D µSCs exhibit state‐of‐the‐art volumetric energy density (16.1 mWh cm^?3) as well as areal (21.3 mF cm^?2) and volumetric (400 F cm^?3) capacitances in 1 m H₂SO₄ aqueous electrolyte. These figures of merit represent the highest values among conducting polymer‐based µSCs. Electrochemical performance is controlled by investigating coating thickness, gap distance, fractal geometry, and gel electrolyte (1 m H₂SO₄/polyvinyl alcohol). The quasisolid‐state µSCs exhibit extended rate capability (50 V s^?1), retain 94% of original capacitance after 10 000 cycles and remain thermally stable up to 60 °C.     

光动力疗法对荷瘤鼠杀伤作用的组织形态学实验研究

目的：探讨光动力疗法恶性肿瘤杀伤作用的机制。方法：应用光动力疗法对接种H22肝癌的40只昆明小鼠作肿瘤杀伤的对比实验研究。结果：通过组织形态学和抑瘤检测证实，光动力疗法能选择性杀伤癌细胞。结论：在治疗后24小时内就可以见到癌细胞出现空泡变性、核固缩、溶解、坏死，随着时间推移坏死更加明显。同时还证实这种光动力疗法对正常细胞和组织没有损伤。     

移动互联网业务欠费控制的实现

移动互联网存在大量的高价值高风险业务,为了实现对欠费风险的控制,提出了基于3GPP实时在线计费概念的网络架构方案,并以CDMA网络为例进行了网元改造说明,对移动互联网实现欠费风险控制方案提供了有力的技术支撑.     

大斜视SAR原始数据的快速模拟算法研究

该文针对小斜视和大斜视模式合成孔径雷达(SAR)提出了两种高效的原始数据模拟算法：变尺度傅里叶变换(SCFT)算法和沿距离向积分算法。基于SCFT的模拟算法将传统的基于2维快速傅里叶变换的2维频域算法推广到斜视模式,采用SCFT取代插值操作,提高了小斜视SAR原始数据模拟的计算效率和仿真精度。沿距离向积分算法适用于大斜视SAR原始数据模拟,保证了大斜视SAR原始数据的模拟精度并同时提高了计算效率。最后,通过仿真证明了这两种算法的有效性。     

Effect of Non‐Chlorinated Mixed Solvents on Charge Transport and Morphology of Solution‐Processed Polymer Field‐Effect Transistors

Using non‐chlorinated solvents for polymer device fabrication is highly desirable to avoid the negative environmental and health effects of chlorinated solvents. Here, a non‐chlorinated mixed solvent system, composed by a mixture of tetrahydronaphthalene and p­‐xylene, is described for processing a high mobility donor‐acceptor fused thiophene‐diketopyrrolopyrrole copolymer (PTDPPTFT4) in thin film transistors. The effects of the use of a mixed solvent system on the device performance, e.g., charge transport, morphology, and molecular packing, are investigated. p‐Xylene is chosen to promote polymer aggregation in solution, while a higher boiling point solvent, tetrahydronaphthalene, is used to allow a longer evaporation time and better solubility, which further facilitates morphological tuning. By optimizing the ratio of the two solvents, the charge transport characteristics of the polymer semiconductor device are observed to significantly improve for polymer devices deposited by spin coating and solution shearing. Average charge carrier mobilities of 3.13 cm² V^?1 s^?1 and a maximum value as high as 3.94 cm² V^?1 s^?1 are obtained by solution shearing. The combination of non‐chlorinated mixed solvents and the solution shearing film deposition provide a practical and environmentally‐friendly approach to achieve high performance polymer transistor devices.     

Packet rescheduling in WDM star networks with real-time servicedifferentiation

In this paper, we propose a novel scheduling scheme, namely priority-differentiated scheduling (PDS), which is designed to handle real-time (high-priority) packets in wavelength division multiplexing (WDM) star networks. PDS allows high-priority packets to preempt the prescheduled low-priority (nonreal time) packets. By scheduling the high-priority packets first, and then having the preempted packets rescheduled, PDS guarantees that the high-priority packets can always achieve the earlier transmission than the others in order to meet the quality of service (QoS) requirements. In addition, it does not sacrifice the performance of nonreal-time packets. As a matter of fact, low-priority packets can also benefit from PDS algorithms. This scheme has the capability of handling channel collision and destination conflict, and it supports variable-length packets. This paper also provides an insight into the data channel selection technique along with PDS. With the proposed algorithm that selects a data channel with minimum scheduling latency (MSL), the channel throughput is improved. The performance of the PDS scheme has been extensively studied by means of numerical simulations     

低碳含量a-Si1-xCx∶H薄膜的化学键结构

利用两种不同激发波长进行Raman测量,研究了低碳含量a-Si1-xCx∶H(～＜20at.%)薄膜的结构特征.采用647.1nm激发时,由于激发光能量接近于各样品的光学带隙,因而在样品中具有较大的穿透深度;而采用488nm激发时,激发光被样品表面强烈吸收.探测深度的变化造成了两种激发下Raman谱出现较大的差异.实验结果表明样品体内存在硅团簇结构,样品的自由表面存在一层高浓度的缺陷层.这两种空间的不均匀性造成了高能激发时Raman谱的TO模频率和半高宽比低能激发时有大的红移和展宽.以上结果证明不同激发波长将造成Raman测量结果的差异.