Novel bilayer structure ZnO based photoanode for enhancing conversion efficiency in dye-sensitized solar cells

ZnO film with a novel bilayer structure, which consists of ZnO nanowire (ZnO NW) arrays as underlayer and polydisperse ZnO nanocrystallite aggregates (ZnO NCAs) as overlayer, is fabricated and studied as dye-sensitized solar-cell (DSSC) photoanode. Results indicate that such a configuration of the ZnO nanocrystallite aggregates on the ZnO nanowire arrays (ZnO-(NCAs/NWs)) can significantly improve the efficiency of the DSSC due to its fast electron transport, relatively high surface area and enhanced light-scattering capability. The short-circuit current density (J_sc) and the energy-conversion efficiency (η) of the DSSC based on the ZnO-(NCAs/NWs) photoanode are estimated and the values are 9.19 mA cm⁻² and 3.02%, respectively, which are much better than those of the cells formed only by the ZnO NWs (J_sc = 4.02 mA cm⁻², η = 1.04%) or the ZnO NCAs (J_sc = 7.14 mA cm⁻², η = 2.56%) photoanode. Moreover, the electron transport properties of the DSSC based on the ZnO-(NCAs/NWs) photoanode are also discussed.     

Influence of pore structure on ion diffusion property in porous TiO2 coating and photovoltaic performance of dye-sensitized solar cells

The ion diffusion in porous TiO₂ coating determines the limiting current density and the photovoltaic performance of a dye-sensitized solar cell. Nano-TiO₂ coatings with unimodal nano-size distribution and bimodal size distribution were deposited by vacuum cold spray to examine the effects of the pore structure on the ion diffusion property and cell performance. Results show that the I₃⁻ ion diffusion coefficient increased with the increase in the mean pore size. The bimodal size distribution of nanometer-sized and submicrometer-sized pores in the coating was found to have a synergistic enhancement effect on the ion diffusion. Better ion diffusion performance contributed to a higher open circuit voltage. The optimal coating thickness (~ 30 μm) was nearly doubled in the cells with bimodal pore size distribution, compared with the previously reported optimal coating thickness (~ 15 μm) in the cell with unimodal pore size distribution. The reason is attributed to the high ion diffusion coefficient which allows a high limiting current density.     

Gel electrolytes containing several kinds of particles used in quasi-solid-state dye-sensitized solar cells

Composite gel electrolytes containing several kinds of particles used as the quasi-solid-state electrolytes in dye-sensitized solar cells (DSSCs) were reported. Mesoporous particles (MCM-41) with unique structures composed of ordered nanochannels were served as a new kind of gelator for quasi-solid-state electrolytes. MCM-41, hydrophobic fumed silica Aerosil R972 and TiO2 nanopatricles P25 were dispersed into gel electrolytes respectively. The solar energy-to-electricity conversion efficiency of these cells is 4.65%, 6.85% and 5.05% respectively under 30 mW·cm-2 illumination. The preparation methods and the particles sizes exert an influence on the performance of corresponding solar cells. Owing to unique pore structures and high specific BET surface area, mesoporous silica MCM-41 was expected to have the potential to afford conducting nanochannels for redox couple diffusion.     

Facile synthesis of ZnO nanobullets/nanoflakes and their applications to dye-sensitized solar cells

In this paper we reported a successful synthesis of ZnO nanobullets/nanoflakes by a simple hydro/solvothermal method employing a mixture of water/ethylene glycol as the solvent, and zinc acetate as the zinc source. The final products were characterized by powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Raman scattering and photofluorescence spectra of the products were also investigated. ZnO with both nanobullets and nanoflakes nanostructures had been comparably studied as active photoanodes in dye-sensitized solar cell (DSSC) system, and the overall light-to-energy conversion efficiency of 1.93% has been achieved for nanobullets based DSSC, while that for ZnO nanoflakes based DSSC has been raised up to 3.64%.     

Effect of polyethyleneimine on the growth of ZnO nanorod arrays and their application in dye-sensitized solar cells

A series of oriented hexagonal wurtzite ZnO nanorod-array films were grown on fluorine-doped tin oxide (FTO) coated glass substrates by chemical process. The effect of polyethyleneimine (PEI) on the structure and micro-morphology of ZnO nanorod array films, as well as the photoelectric conversion properties in dye-sensitized solar cells (DSSCs) was analyzed. It was found that with the addition of PEI in growth solution, the ZnO nanorods became smaller in diameter and longer in length and hence the dye absorption and the photovoltaic performance of DSSCs were improved. A power conversion efficiency of 2.30% had been achieved on a DSSC based on a 7.9 μm-long nanorod array film prepared by a growth solution containing the PEI.     

The double-edged function of UV light in polymer solar cells with an inverted structure

Inverted polymer solar cells with a configuration of ITO/ZnO/PBDTTT-C:PC₇₁BM/MoO₃/Ag were fabricated and a power conversion efficiency of 6.64% was achieved under AM 1.5G irradiation (89 mW/cm²). The function of UV light was systematically investigated by tracking the changes of the device performance for 212 min under continuous illumination with or without UV light. We found that UV light plays a decisive role not only in the photo-annealing step, leading to a remarkable increase of PCE by increasing ZnO conductance, but also in the photo-bleaching step, causing slow degradation of solar cells through photo-oxidation of the conjugated polymer.     

Preparation of doping metal TiO2 particle/nanotube composite layer and their applications in dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) are composed of a dye-adsorbed nanoporous TiO₂ layer on a fluorinedoped tin oxide (FTO) glass substrate, redox electrolytes, and a counter electrode. DSSCs are constructed through the application of nano-metals and TiO₂ nanoparticle/TiO₂ nanotube (TNT) composite particles with various compositions. The use of oxide semiconductors in the form of nanorods, nanowires, and nanotubes is an interesting approach to improve electron transport through the film. In addition, a suitable amount of TNT in the film could provide a large surface area for the adsorption of the dye. A nano-metal is proposed, wherein the conduction band (CB) prohibits the trapping effects of electrons within the TiO₂ conduction band. This result is attributed to the prevention of electron recombination between the electrons in the TiO₂ conduction band with dye or electrolytes. A TiO₂ composite layer was coated onto FTO glass using a screen-printing method. The dye-sensitized solar cells were fabricated using N719 ruthenium (II) dye and I₃/I₃ ^? electrolyte. The impedance results indicate improved electron transport at the TiO₂/dye/electrolyte interface. The DSSC based on the Fe₂O₃/TiO₂/TNT composite particle hybrids exhibits better photovoltaic performance than the cell made from only TiO₂ nanoparticles.     

组成相中微观应力和应变对钛合金力学性能的贡献

分析组成相对钛合金力学性能的贡献对组织设计极为重要。通过真实组织有限元模型定量分析了α<sub>p</sub>和β<sub>t</sub>中的应力和应变,并确定了他们对Ti-6Al-2Zr-1Mo-1V钛合金强度和韧性的贡献。结果表明,α<sub>p</sub>和β<sub>t</sub>中的应力呈现正态分布。β<sub>t</sub>的峰值应力和应力峰高远大于α<sub>p</sub>。然而,α<sub>p</sub>具有较大的峰值应变,β<sub>t</sub>具有较大的应变峰高。随着α<sub>p</sub>体积分数从49%降低到12%,β<sub>t</sub>对抗拉强度的贡献从59%增加到92%,对失效应变的贡献从36%增加到75%。然而,随着β<sub>t</sub>贡献的增加,合金抗拉强度增加了17%,失效应变降低了21%。研究结果定量揭示了组成相对强度和韧性的贡献,为钛合金组织设计提供了基础。     

铁素体不锈钢中铜析出相的长大和晶体结构演化规律研究

为研究铁素体不锈钢中铜析出相的析出过程和晶体结构演化规律,采用原子探针层析技术(APT)和高分辨透射电子显微镜(HRTEM)观察了铜析出相的长大过程.结果显示:随着时效时间的延长,富铜相尺寸增大,数量密度降低,析出相形状由最初的球状转化为椭球状,最后成为杆状.析出相长大曲线可以拟合为(r-)t = 2.45t1/3-4...     

Wave propagation in water-immersed adhesive structure with the substrates of finite thickness

In previous theoretical studies on the adhesive structure, the substrate is mostly considered as a semi-infinite solid space and corresponding theoretical derivation is rarely related to the thickness of the substrate. In the paper, based on the transfer matrix method, we studied in the water-immersed trilaminar plate-like adhesive structure with the substrates of finite thickness and the perfect/sliding interfaces in the case of plane longitudinal wave incidence and deduced the expressions of reflection and transmission coefficients of longitudinal waves. In order to verify the accuracy and applicability of the deduced formula, this formula was firstly applied to the water-immersed steel–epoxy resin–steel adhesive structure with perfect interfaces and the calculated result was compared with the existing data. Taking the water-immersed aluminum–epoxy resin–aluminum adhesive structure with perfect/sliding interfaces as an example, the impacts of incident angle and frequency on the reflection and transmission characteristics of the longitudinal wave were then analyzed. Finally, the theoretical method was experimentally verified and the experimental results were well consistent with the numerical calculation results. The reflection and transmission coefficient curves of longitudinal wave showed the obvious resonance when the longitudinal wave was normally incident. Regardless of the substrate thickness, the frequency of acoustic waves or the incident angle, it can only confirm whether a sliding interface exists, but the interface to slide cannot be determined.     

Effects of annealing conditions on the properties of TiO2/ITO-based photoanode and the photovoltaic performance of dye-sensitized solar cells

Photovoltaic performance of dye-sensitized solar cell (DSSC) is enhanced by a two-step annealing process of the photoanode. The 1st-step of annealing is performed in oxygen at 450 °C for 30 min which effectively removes the residual organics originated from the TiO₂ precursor pastes. This enhances the dye adsorption on the TiO₂ nanoparticles and raises the short-circuit current density (J_SC). The 2nd-step of annealing is performed in nitrogen at 450 °C for 10 min which removes extra oxygen atoms resulted from the incorporation of oxygen atoms into the tin-doped indium oxide (ITO) film during the 1st-step of annealing. This reduces the sheet resistance of ITO and thereby enhances the fill factor (FF). With the enhanced J_SC of 15.9mAcm⁻² and FF of 0.65, the AM1.5 solar to electric conversion efficiency (η) of DSSC reaches 6.7% which is better than that based on the conventional one-step air annealing (η = 5.53%, J_SC = 14.08 mA cm⁻², FF = 0.6).     

The creep behaviour of the ILZRO14 zinc alloy

Microstructural characterization of the ILZR014 alloy shows that it is made up of η phase dendrites, containing ε precipitates, bordered by a multiphased interdendritic zone, consisting of the η/TiZn₁₅ lamellae eutectic and the B phase. The microstructure of this alloy was correlated with the (Zn—Cu—Ti) phase diagram. The TiZn₁₅ lamellae eutectic and the fine semi-coherent ε precipitates play a major role on creep behaviour. It is found that the modification of this alloy by the suppression of the ε phase or by the spheroidisation of the TiZn₁₅ lamellae leads to a deterioration of the creep behaviour. The creep behaviour of the ILZR014 alloy was compared with that of another zinc alloy, ZAMAK5, in which the destabilisation of the interdendritic zone occurs during creep testing.     

Charge transport and recombination in dye-sensitized solar cells based on hybrid films of TiO2 particles/TiO2 nanotubes

In this paper, anodic TiO₂ nanotubes are blended into the TiO₂ mesoporous films based on P25 nanoparticles to assemble a list of dye-sensitized solar cells (DSSCs) with different nanotube concentrations. The electron properties of transport and recombination in the fabricated DSSCs are studied by using electrochemical impedance spectroscopy and the open-circuit voltage decay technique under AM 1.5 illumination. Results indicate that the electron lifetime increases with increasing the concentration of the anodic TiO₂ nanotubes, the electron transport time at a blending level of 10 wt% TiO₂ nanotubes is short as compared to that at 0 wt%, and above 10 wt%, the electron transport time has a trend of becoming large. Due to the combining effects of the electron transport and recombination, the electron collecting efficiency and the electron diffusion length obtain maxima at a blending level of 10 wt% nanotubes, which results in a highest short circuit current and a maximum energy conversion efficiency at this point in the DSSCs. This study gives a clear explanation for the performance enhancement of TiO₂ particle-based DSSCs at a blending level of 10 wt% anodic TiO₂ nanotubes and for the performance decrease at a blending level over 10 wt% anodic TiO₂ nanotubes from the angle of the electron transport and recombination. This study also supplies a feasible and easy way to improve the performance of particle-based DSSCs by restraining electron recombination and accelerating electron transportation.     

Modification of poly(ethylene oxide) electrolyte by Brönsted base terminated oligo(ethylene glycol) and its application in dye-sensitized solar cells

Oligo(ethylene glycol) terminated by pyridine derivatives was designed and synthesized for improving the performance of the dye-sensitized solar cells (DSCs) with poly(ethylene oxide) based electrolyte. Effects of the plasticizer on retarding the recombination reaction in DSCs were characterized by current density–voltage characteristics. Combined with the results on electron density measurements, photovoltage–intensity characteristics correlate the retarded electron recombination with the upward movement of the conduction band edge and the reduced order of recombination reaction. The increased electron lifetimes of the DSCs with plasticizer modified electrolyte were confirmed by a small perturbation voltage decay technique. Additionally, WAXS measurements show that the presence of the plasticizer decreases the crystallinity of PEO electrolyte, which facilitates the mass transport of the redox species as impedance spectra indicated. By introducing guanidinium thiocyanate into the plasticizer modified PEO electrolyte, the performance of the DSCs is further improved, which yields the highest efficiency of 3.5%.     

重型液压设备本体结构的发展与创新

重型液压设备的性能是衡量一个国家大锻件制造业水平的重要标志,也是一个国家综合实力的体现。本文综述国内外重型液压设备的发展历程,重点论述了重型液压设备承载结构的发展与创新。由于液压机工作时是一个封闭受力系统,本体结构作为液压机的重要承力构件,均承受高负荷、复杂加载,由于质量大,制造难度也大。重型模锻设备从最初的梁-柱结构转变为厚钢板组合框架结构,再发展到粗螺栓预紧结构,以及螺栓预紧和钢丝缠绕预紧的剖分-组合结构,最近广泛采用的钢丝缠绕预紧的剖分-坎合结构,不同时期的重型锻压设备的本体结构的设计既受所处时代制造能力的限制,也具备不同时期的创新特点。缸梁一体式液压机作为一个创新概念的提出,也为重型设备的发展提供一个可供参考的思路。     

大型薄壁箱形体的结构优化

将复杂的箱形结构简化为空间板系组合结构 ,使结构有限元分析和优化准则法有效地结合 ,开发了用于箱形结构优化设计的程序 ,实现了箱形结构尺寸的合理确定。通过对某水压机的箱形横梁进行的优化设计表明 ,利用该程序对箱形结构进行优化设计是可行的。     

热柱毛细芯中铜纤维和微沟槽黏附力的研究

通过多齿铣削和高温烧结制造了微沟槽烧结铜纤维板,通过超声波振动实验测试了烧结参数和铜纤维参数对复合毛细芯中铜纤维和微沟槽壁面黏附力的影响,结果表明:烧结时间、烧结温度、温度上升速率、烧结压力以及纤维参数对热柱复合毛细芯中的铜纤维和微沟槽壁面的黏附力有重要的影响。当烧结温度为900摄氏度,烧结时间60 min,烧结压力为0.45 MPa,温度上升速率为5℃/s下烧结的烧结层厚度为1 mm时的复合毛细芯中的铜纤维和微沟槽壁面的黏附力最大。     

钙钛矿太阳能电池稳定性的研究进展

回顾了钙钛矿太阳能电池的发展历程,总结了影响钙钛矿太阳能电池稳定性的几个重要因素,包括水汽、氧气、光照和高温条件对钙钛矿层的化学稳定性以及电子传输层(ETL)、空穴传输层(HTL)和制备工艺对电池稳定性的影响。对稳定机制进行了分析,提出了改善稳定性的一些方法,并根据目前的研究成果展望了钙钛矿太阳能电池的发展趋势。     

The structure and bonding of Ni3Sn

The electronic structure of Ni₃Sn was calculated at ab initio levels for the crystal structure of the low-temperature modification of Ni₃Sn refined upon data of single-crystal X-ray diffractometry (P6₃/mmc, a=5.2950(7), c=4.247(1) Å, R=0.0288). The calculations were made with the use of fixed Gaussian (CRYSTAL98 software) and energy-dependent (Stuttgart TB-LMTO-ASA software) basis sets. Difference electron charge density maps were analysed and compared with that of a hypothetical hcp Ni in order to understand bonding in Ni₃Sn. It was found that bonding in Ni₃Sn has multicentre character with Ni–Sn interaction stronger than Ni–Ni one.     

Formation of embedded fine copper patterns in various resins by the transfer of plated metal patterns

A combination of two techniques was used to form metal patterns embedded in flexible resin films. First, metal patterns were formed on sacrificial glass substrates using a photodefinable metal complex solution to form a latent catalyst image. Then, copper was selectively deposited on the catalyst image by electroless plating. In the first step, copper mesh patterns with ca. 90%T visible light transmittance and sheet resistance less than 1?Ω/□ were formed on glass substrates. In the next step, copper patterns were transferred by forming flexible thin resin films on sacrificial glass surfaces with the copper patterns, then curing the resin and delaminating the resin films from the glass. Height differences on the nanometre scale between the film surface and embedded copper pattern showed that complete embedding of the copper structures was attained. After the transfer, change in the optical and electrical properties of the mesh pattern was not detected.