Correlation of band electronic structure with efficiency in perovskite solar cells with vanadium (Ⅳ) oxide thin film buffers

Perovskite solar cells have been studied extensively in the area of perovskite solar cells because they have a comparatively free hysteresis. Through fabrication of a perovskite solar cell based on a vanadium oxide buffer, this study clarified the mechanism of electron and hole transport in the laminated layer upon irradiation with light. The power conversion efficiency (PCE) of the Vanadium (Ⅳ) oxide (VO₂) sputtering process device was approximately 13% and with the spin-coating process was 8.5%. To investigate the physicochemical origin of such PCE differences depending on the process type, comprehensive band alignment and band structure analyses of the actual cell stacks were performed using X-ray photoelectron spectroscopy depth measurements. Accordingly, it was found that the inconsistent valence band offset between the perovskite absorption layer and V₂O₅ layer as a function of the VO₂ process type caused a difference in the hole transport, resulting in the difference in the efficiency.     

有机光伏器件激活层的微结构有序性与电荷输运

本文在对有机光伏电池载流子产生机理分析的基础上,从有机光伏电池激活层的微观结构对光电转换效率影响的角度,系统介绍了目前该领域的一些重要研究成果,详细分析了影响光电转换效率的主要因素,并提出了一系列改善光伏电池效率的方法,对未来该领域的研究作了展望。     

PARTICULATE CONCENTRATION ENRICHMENT OF PRIMARY AIR IN PULVERIZED COAL BOILERS

Particulate concentration enrichment (PCE) of primary air favors flame ignition and stabilization, and the reduction of NOx emission in pulverized coal combustion. The methods used for PCE are summarized in five categories:Cyclone PCE, Elbow PCE, Blunt-body PCE, Hydrodynamic PCE and Swirling PCE. Practice of each PCE method is illustrated with typical burners and the associated pros and cons are discussed. It is found that the same principle prevails in all PCE methods, that is, due to inertial difference, solid particles preferentially decelerate and separate from the gas stream when the main flow deviates in flow orientation. From analysis of various P-C burners, PCE design is deemed to yet comprise “rule of thumb” practice. Some discussions regarding PCE application are given.     

Comparison of perchloroethylene extraction techniques in soil gas survey quantification

Subsurface pollution by volatile organic compounds has emerged as a widespread problem in industrialized countries. This study compares static headspace technique and methanol extraction/purge-and-trap analysis followed by thermal desorption/gas chromatography in attempts for quantification of gas survey results in the determination of these chemicals in soil. Several soils were contaminated with aqueous solution of perchloroethylene (PCE) (140 mg L⁻¹) using a vapor treatment method. Soil spiking took place up to 24 h in desiccator by exposing individual soil samples contained in open 40 mL glass vials to PCE evaporated from the solution. After exposure the samples were stored and analyzed within 2 days. The achieved results strongly suggest that gas extraction can provide quantitative results, regarding PCE concentration in soils, which are not significantly different from liquid based extraction analysis.      

Reductive dechlorination of tetrachloroethylene (PCE) catalyzed by cyanocobalamin

A biomimetic system has been developed for the reductive dechlorination of tetrachloroethylene (PCE). PCE was dechlorinated to trichloroethylene (TCE) and 1,2-dichloroethylene (DCE) in the presence of dithiothreitol or Ti (III) citrate and catalytic amounts of cyanocobalamin in both homogeneous reaction mixtures and packed bed reactor systems. In packed bed reactors with Ti (III) citrate as the reductant, PCE (0.18 mM) conversion averaged 55% at residence times of 1.75 and 3.5 h. The product distribution was 94% TCE and 6% DCE at the lower residence time. DCE formation increased to 45% at the higher residence time. No reduction of PCE was observed in the absence of cyanocobalamin. This system may be useful as a means of pretreatment of halogenated aliphatic hydrocarbons in advance of biological treatment.     

基于多项式混沌拓展模型和bootstrap的结构可靠性分析方法

多项式混沌拓展(polynomial chaos expansion,PCE)模型现已发展为全局灵敏度分析的强大工具,却很少作为替代模型用于可靠性分析。针对该模型缺乏误差项从而很难构造主动学习函数来逐步更新的事实,在结构可靠性分析的框架下提出了基于PCE模型和bootstrap重抽样的仿真方法来计算失效概率。首先,对试验设计(experimental design)使用bootstrap重抽样步骤以刻画PCE模型的预测误差;其次,基于这个局部误差构造主动学习函数,通过不断填充试验设计以自适应地更新模型,直到能够精确地逼近真实的功能函数;最后,当PCE模型具有足够精确的拟合、预测能力,再使用蒙特卡洛仿真方法来计算失效概率。提出的平行加点策略既能在模型更新过程中找到改进模型拟合能力的"最好"的点,又考虑了模型拟合的计算量;而且,当失效概率的数量级较低时,PCE-bootstrap步骤与子集仿真(subset simulation)的结合能进一步加速失效概率估计量的收敛。本文方法将PCE模型在概率可靠性领域的应用从灵敏度分析延伸到了可靠性分析,同时,算例分析结果显示了该方法的精确性和高效性。     

Computational engineering to enhance the photovoltaic by end-capped and bridging core alterations: Empowering the future with solar energy through synergistic effect in D-A materials

Organic photovoltaic solar cells are being designed to offer a low energy photovoltaic (PV) solution. Optimizing the molecular backbone is one the most important technique for improving the photovoltaic characteristic of A-D-A type small active layer molecules. Herein, we have designed and theoretical characterized six new molecules by end-capped and bridging core modifications of recently synthesized molecule BFHIC-4F. Enhancement in photovoltaic, optoelectronic and physio-chemical properties of newly designed molecules are seen by doing such modifications. Different advanced quantum chemical techniques have been employed to evaluate the performance of newly planned molecules. Large open circuit voltage and narrow band gap suggested that the designed molecules are efficient aspirants for solar cell applications. Moreover, maximum absorption capability in near-infra-red (NIR) region is observed for these newly designed molecules. To sum up, outcomes of all analyses advocated that the designed molecules are efficient candidates for solar cell applications.     

Visualization of DNAPL Fingering Processes and Mechanisms in Water-Saturated Porous Media

Groundwater contamination by dense nonaqueous phase liquids (DNAPLs) has received increasing attention in the last decade. The fingering process of DNAPL migration in porous media remains an incompletely understood subject. The main reason is that natural porous media are opaque and hence very few visualizations are available. This paper presents the visual results of two-dimensional experiments in a glass tank in which DNAPL penetrated into water-saturated homogeneous porous media. The results provide a clear reference for conceptual models of DNAPL finger development due to immiscible flow instabilities. The fingering process can be divided into two stages, that is, the finger initiation stage and the finger elongation stage. At the finger initiation stage, many DNAPL protuberances appear at the interface between tetrachloroethylene (PCE) and water along the surface of the porous media. During the finger elongation stage, some relatively larger protuberances develop into primary fingers. Secondary fingers may develop on the existing primary fingers. The fingers grew downwardly in a winding manner with the mechanisms of shielding, tip-growing, splitting, and coalescing. The fingers grew linearly with time and had simi-lar growth rate at the finger elongation stage. The average wavelength (space between fingers) of the primary fingers was 0.051m and the average PCE content in the region with fingers was 2.5% (7.0% saturation).