Photovoltaic performance of Gallium-doped ZnO thin film/Si nanowires heterojunction diodes

In this work, photovoltaic performance of Ga-doped ZnO thin film/Si NWs heterojunction diodes was investigated. Highly dense and vertically well-aligned Si NW arrays were successfully synthesised on a p-type (1?0?0)-oriented Si wafer through cost-effective metal-assisted chemical etching technique. Ga-doped ZnO thin films were deposited onto Si NWs via radio frequency magnetron sputtering to construct three-dimensional heterostructures. Photovoltaic characteristics of the fabricated diodes were determined with current density (J)–voltage (V) measurements under simulated solar irradiation of AM 1.5 G. The optimal open-circuit voltage, short-circuit current density, fill factor and power conversion efficiency were found to be 0.37 V, 3.30 mA cm^?2, 39.00 and 0.62%, respectively. Moreover, photovoltaic diodes exhibited relatively high external quantum efficiency over the broadband wavelengths between 350 and 1100 nm interval of the spectrum. The observed photovoltaic performance in this study clearly indicates that the investigated device structure composed of Ga-doped ZnO thin film/Si NWs heterojunctions could facilitate an alternative pathway for optoelectronic applications in future, and be a promising alternative candidate for high-performance low-cost new-generation photovoltaic diodes.     

Low defect-density polycrystalline silicon for high performance thin film transistors

Polysilicon films formed by the decomposition of silane in a LPCVD reactor at temperatures around 630°C have been used to make thin film transistors. It has been found that deposition of the polysilicon at lower pressures than previously results in improved performance and this is related to the crystallographic structure of the material. The structure of polysilicon deposited at pressures down to 2.5 mTorr has been investigated and the results presented.     

Polarized memory effect in Se thin film diodes

Polarized memory effect in thin film of SnO₂SeCu structure, in which Cu electrode is deposited, is observed. Current-voltage characteristics and impedance characteristics of this element are described.     

Fabrication and characterization of thermal evaporated n-Si/ p-ZnTe thin film heterojunction diodes

The paper reports the fabrication and detailed electrical characterization of thermal evaporated n-Si/p-ZnTe thin film heterojunction diodes. The heterojunction diodes were prepared by depositing ZnTe films on n-Si substrates. The conduction mechanism, barrier height, space charge density and width of the depletion region were determined by I–V and C–V characteristics of the heterojunction diodes. The bandgap and activation energies of n-Si and p-ZnTe were also determined and a theoretical band diagram of n-Si/p-ZnTe heterojunction was drawn based on Anderson's model.     

Molecular recoiling in polymer thin film dewetting

The molecular recoiling force stemming from nonequilibrium chain conformation was found to play a very important role in the dewetting stability of polymer thin films. Correct measurements and inclusion of this molecular force into thermodynamic consideration are crucial for analyzing dewetting phenomena and nanoscale polymer chain physics. This force was measured using a simple method based on contour relaxation at the incipient dewetting holes. The recoiling stress was found to increase dramatically with molecular weight and decreasing film thickness. The corresponding forces were calculated to be in the range from 9.0 to 28.2 mN/m, too large to be neglected when compared to the dispersive forces (approximately 10 mN/m) commonly operative in thin polymer films.     

Drying of thin film polymer solar cells

Our focus of investigations is on the dependency of the polymer solar cell (PSC) characteristics on drying conditions like temperature and kinetic effects. We optimized the homogeneity for the doctor bladed active layer in conjunction with viscosity measurements, examined the dependency of cell characteristics on drying kinetics with best results at slow drying and accomplished differential scanning calorimetry (DSC) with solution-processed samples in the typical annealing temperature range.     

修饰阴极界面提高聚合物白光二极管发光效率

利用聚合物的不同溶解性,研究用旋涂方法制备双层高分子白光二极管(WPLED),采用器件结构为：ITO/PEDOT(50nm)/PVK:PFO-BT: PFO-DBT(40nm)/PFO(40nm)/Ba(4nm) /Al(120nm),当相对比例为PVK: PFO-BT:PFO-DBT=1∶4%：3%时,得到标准白光,最大电流效率为2.4 cd/A,最大亮度为3215 cd/m²,色坐标为(0.33,0.34).用水溶性的聚电介质层修饰阴极界面,器件效率可以进一步提高到5.28 cd 关键词： 聚合物发光二极管 白光 双发光层结构     

A1GaInP-Si glue bonded high performance light emitting diodes

We propose a new method of using conductive glue to agglutinate GaAs based A1CaInP light emitting diodes （LEDs） onto silicon substrate, and the absorbing GaAs layer is subsequently removed by grinding and selective wet etching. It was found that A1GaInP-Si glue agglutinated LEDs have larger saturation current and luminous intensity than the conventional LEDs working at the same injected current. The luminous intensity of the new device is as much as 1007.4 mcd at a saturation current of 125 mA without being encapsulated, while the conventional LEDs only have 266.2 mcd at a saturation current of 105 mA. The luminescence intensity is also found to increase by about 3.2% after working at 50 mA for 768 h. This means that the new structured LEDs have good reliability performance.     

用准光波导方法测量聚合物薄膜光学参数

本文报道用准光波导方法测量了沉积在棱镜底面上的聚苯乙烯和聚醚砜薄膜,确定了这两种聚合物薄膜的折射率和薄膜厚度.并用偏振光测定了其双折射.薄膜折射率测量误差为±1×10~(-3),薄膜厚度测量误差为±0.01μm.     

Ordered macroporous gold thin film with encaptured polymer spheres

A two-dimensional colloidal crystal fabricated from core-shell polystyrene spheres was employed as a template for the electrochemical deposition of gold. By partially embedding the colloidal spheres into the gold film and selectively removing the shells of the colloidal spheres, highly ordered macroporous gold thin films with captured polystyrene spheres were obtained.     

Enhancing the performance of thin film CdS/PbS photovoltaic solar cells

This work investigates dependence of the short-circuit current density, open-circuit voltage, fill factor and efficiency of a thin film CdS/PbS solar cell on thickness of transparent conductive oxide (TCO) layer, thickness of window layer (CdS), concentration of uncompensated acceptors (width of space-charge region), carrier lifetime in PbS and the reflectivity from metallic back contact. The effect of optical losses, front and rear recombination losses as well as the recombination losses on space-charge region are also considered in this study. As a result, by thinning the front contact layer indium tin oxide from 400 to 100 nm and window layer (CdS) from 200 to 100 nm it is possible to reduce the optical losses from 32 to 20%. The effect of electron lifetime on the internal and external quantum efficiency can be neglected at high width of the space-charge region. The maximum current density of 18.4 mA/cm² is achieved at wide space-charge region (concentration of uncompensated acceptors = 10¹⁵ cm^?3) and the longest lifetime (τ_n = 10^?6 s) where the optical and recombination losses are about 55%. The maximum efficiency of 5.17%, maximum open-circuit voltage of 417 mV and approximately fixed fill factor of 74% are yielded at optimum conditions such as: electron lifetime = 10^?6 s; concentration of uncompensated acceptors = 10¹⁶ cm^?3; thickness of TCO = 100 nm; thickness of CdS = 100 nm; velocity of surface and rear recombination = 10⁷ cm/s and thickness of absorber layer = 3 μm. When the reflectance from the back contact is 100%, the cell parameters improve and the cell efficiency records a value of 6.1% under the above conditions.     

AlGaInP-Si glue bonded high performance light emitting diodes

We propose a new method of using conductive glue to agglutinate GaAs based AlGaInP light emitting diodes (LEDs) onto silicon substrate,and the absorbing GaAs layer is subsequently removed by grinding and selective wet etching.It was found that AlGaInP-Si glue agglutinated LEDs have larger saturation current and luminous intensity than the conventional LEDs working at the same injected current.The luminous intensity of the new device is as much as 1007.4 mcd at a saturation current of 125 mA without being encapsulated,while the conventional LEDs only have 266.2 mcd at a saturation current of 105 mA.The luminescence intensity is also found to increase by about 3.2% after working at 50 mA for 768 h.This means that the new structured LEDs have good reliability performance.     

Acoustical performance of an electrostrictive polymer film loudspeaker

A new type of loudspeaker that generates sound by means of the electrostrictive response of a thin polymer film is described. Electrostrictive polymer film (EPF) loudspeakers are constructed with inexpensive, lightweight materials and have a very low profile. The films are typically silicone and are coated with compliant electrodes to allow large film deformations. Acoustical frequency response measurements from 5 x 5 cm (planar dimensions) prototype EPF loudspeakers are presented. Measurements of harmonic distortion are also shown, along with results demonstrating reduced harmonic distortion achieved with square-root wave shaping. Applications of EPF loudspeakers include active noise control and general-purpose flat-panel loudspeakers.     

自持铝薄膜的工艺和特性研究

铝薄膜在像管中起重要作用。为了提高像管的性能 ,需要对自持铝薄膜的特性加以研究。利用静电贴膜技术制备了自持铝薄膜 ,测量了 5 0nm厚自持铝薄膜入射面的背散射系数和二次发射系数以及出射面的一次电子透射系数和二次发射系数。对于高能一次入射电子 ,自持铝薄膜的背散射系数很小 ,透射系数很大 ,二次发射系数较小。自持铝薄膜在本质上不影响像管的MTF ,由其出射面发射的二次电子对像管亮度有增强作用     

Optimization of conducting polymer thin film optical and electrical waveguides

The fabrication and characterization of conducting polymer thin film optical and electrical waveguides prepared by vacuum deposited method is reported. The waveguiding parameters (refractive index, propagation loss, V-I and C-V characteristics) have been measured.     

Real-time monitoring of all-optical poling of azo-dye polymer thin film

Simultaneous writing and probing of photoinduced second-order susceptibility chi((2)) in an azo-dye polymer thin film is demonstrated. The method is based on the fact that tensor properties of chi((2)) provide different planes of polarization for seeding and signal second harmonics. Our technique allows the chi((2)) value to be monitored in real time, completely eliminating the distortion of optical poling that can occur in traditional probing configurations. The possibility of attaining high values of chi((2)) in a DR1-PMMA guest?host system under low seeding intensities is shown.     

多层高温超导薄膜研究

文中以LaAlO3为衬底,制作了一层Tl-2212高温超导薄膜,并在薄膜上生长一层较薄的CeO2缓冲层,然后再在上面生长一层Tl-2212高温超导薄膜。经过测量,研究了多层膜结构对超导薄膜临界电流密度的影响。结果显示,在缓冲层的结晶过程中超导薄膜的晶格受到影响,结晶过程中的处理很容易诱导上面一层Tl-2212超导薄膜产生杂相,导致临界电流密度降低。     

Room-temperature flexible thin film transistor with high mobility

We report a room-temperature and high-mobility InGaZnO thin-film transistor on flexible substrate. To gain both high gate capacitance and low leakage current, we adopt stacked dielectric of Y₂O₃/TiO₂/Y₂O₃. This flexible IGZO TFT shows a low threshold voltage of 0.45 V, a small sub-threshold swing of 0.16 V/decade and very high field-effect mobility of 40 cm²/V. Such good performance is mainly contributed by improved gate stack structure and thickness modulation of IGZO channel that reduce the interface trap density without apparent mobility degradation.     

Ablation of polymer foils for backside opening of thin film layered flexible polymer substrates

For increasing the packing density of electronic devices and enabling 3D wiring, new concepts of interconnection for flexible circuit boards are required. The backside wiring is one innovative concept which, however, requires interconnections from the back to the front side by means of vias.Results on backside opening of polymer foils for exposing a thin metal film deposited at the front side are presented. For the experiments, a thin polyimide foil covered with a thin molybdenum metal film was used. By using mask projection of a pulsed UV-laser beam (248 nm, 20 ns) polymer foil was ablated. The laser ablation process must be adjusted in the manner to avoid damage of the thin metal film, to prevent cones formation at laser ablation, but still enabling the clean ablation of the polymer. The influence of process parameters on the backside opening is discussed and compared with theoretical estimations of the laser-induced temperatures. Using a two-step ablation process applying first high fluences to ablate the main part of the foil and finishing with low laser fluence turns out to be advantageous. This backside opening (BSO) can be used to perform an electrical contact from the backside.