Sensitivity analysis of full field methods for residual stress measurement

The hole drilling technique is a well known experimental method for residual stress investigation. This technique is usually used in combination with electrical strain gauges but there is no reason to enforce this choice and other approaches, in particular some full-field optical techniques, can be advantageously used. Since all these techniques give full field data, it becomes important to properly use this redundant information content to increase the robustness and reliability of the analysis.In this work, various well known approaches to the hole drilling/full-field data analysis will be investigated using a two-step approach. In the first one, a sensitivity analysis will be performed on the simpler algorithms and then the reliability of the methods will be estimated by Montecarlo analysis using a known displacement field as a reference.     

Impact of replacement of the central benzene ring in anthracene by a heterocyclic ring on electronic excitations and reorganization energies in anthratetrathiophene molecules

The impact of changing the central benzene ring on the electronic excitations and reorganization energies (λ) of the anthratetrathiophene (ATT) molecules is studied by density functional theory (DFT) and time‐dependent DFT (TD‐DFT) quantum chemical calculations. The effect of changing the position of the sulfur atom at the periphery of anthracene on the optical and charge transfer properties is also studied. The calculated results suggest that the HOMO, LUMO, HOMO–LUMO energy gap, ionization potential (IP), electron affinity (EA), hole extraction potential (HEP), electron extraction potential (EEP), and reorganization energies (λ) are affected by replacing the central ring with different heterocyclic rings and the position of the sulfur atom. In addition, all molecules show good hole‐ and electron‐transport properties. This work may be helpful for future design and preparation of high‐performance charge‐transport materials.     

BePP_2沉积速率以及厚度对蓝光OLED性能的影响

实验采用真空热蒸镀方法,在高准确度膜厚控制仪的监控下,制备了结构为ITO/2T-NATA(25nm)/NPB(30nm)/BePP2(X nm)/Alq3(30nm)/LiF(0.6nm)/Al(80nm)的蓝光器件,并对其发光层(BePP2)薄膜的沉积速率以及厚度对器件的亮度、发光效率影响进行了分析和实验研究.结果表明:当束源炉孔径为Φ1.5mm,束源炉温度在120℃~150℃区域,BePP2的蒸镀速率比较平滑,斜率变化小,易于膜厚精准控制,且薄膜较致密满足器件需要;BePP2在最佳沉积速率为0.02nm/s(蒸发温度为135℃),且发光层厚度为35nm时,可获得启亮电压为5.34V、发光亮度为9 100cd/m2、发光效率达4.4cd/A的较理想蓝光器件.     

Dark current suppression of amorphous selenium based photosensors by the ZnO hole blocking layer

To study the influence of defects in the hole blocking layer (HBL) on the dark current of amorphous selenium (a-Se) based photosensors, we prepared ZnO thin films by reactive sputter deposition (RSD) for the use as the HBL of the photosensors. The ZnO HBL layers prepared with different oxygen flow rates were characterized by X-ray photoelectron spectroscopy, Raman scattering analysis and photoluminescence, indicating that the density of oxygen vacancies in the ZnO thin films is significantly affected by the oxygen flow rate. The deep level transient spectroscopy measurement reveals two hole trap levels present in the RSD deposited ZnO thin films; one is at 0.94 eV and the other at 0.24 eV above the valence band edge. The electrical performance of the a-Se photosensor is largely influenced by the amount of oxygen vacancies in the ZnO thin film. The a-Se photosensor with the ZnO HBL of the most oxygen vacancies has the lowest dark current and demonstrates the highest breakdown field.     

Microwave-reduced graphene oxide for efficient and stable hole extraction layers of polymer solar cells

Microwave-assisted reduced graphene oxide (MR-GO) layer was applied to hole extraction layer (HEL) of polymer solar cells (PSCs) and was compared with the widely used poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) in bulk hetero-junction (BHJ) solar cells. The power conversion efficiency (PCE) of 3.57% was achieved with the MR-GO layer, which is 21% higher than that of PSCs with the conventional PEDOT:PSS HEL material. This enhancement of PCE is mainly attributed to the increase of short-circuit current density originated from the hydrophobic surface of the MR-GO layer. The hydrophobic graphene oxide surface is believed to improve wetting property and physical contact of active blends. In addition, the MR-GO interfacial layer is found to show the excellent device stability in atmospheric condition. The PCE of conventional PEDOT:PSS based PSCs showed total degradation when the device was exposed to atmospheric condition for 1000 h without any encapsulation, while that of MR-GO based PSC showed over 85% of PCE.     

基于应变锗空穴双量子点的可调耦合和自旋阻塞研究

应变锗空穴量子点是实现超大规模量子计算最有前景的平台之一.由于锗空穴不受超精细相互作影响，有着较长的自旋弛豫时间和量子退相干时间，且锗中本征的强旋轨道耦合和空穴载流子的低有效质量，使得全电场操控空穴自旋量子比特得以实现，极大地降低了器件加工难度，增加了量子点的可扩展性.本文介绍了一种使用应变锗异质结制备重叠栅空穴双量子点器件的方法，完成了应变锗异质结性质测量，空穴双量子点器件制作，单量子点输运性质和双量子点输运性质研究，双量子点耦合可研究调节性研究，以及外磁场存在下的漏电流性质研究和泡利自旋阻塞解除机制的研究.这些工作为未来实现高质量自旋量子比特制备和高保真度量子逻辑门操控提供了实验平台和基本参数.     

Design Principles for Maximizing Hole Utilization of Semiconductor Quantum Wires toward Efficient Photocatalysis

Maximizing hole-transfer kinetics—usually a rate-determining step in semiconductor-based artificial photosynthesis—is pivotal for simultaneously enabling high-efficiency solar hydrogen production and hole utilization. However, this remains elusive yet as efforts are largely focused on optimizing the electron-involved half-reactions only by empirically employing sacrificial electron donors (SEDs) to consume the wasted holes. Using high-quality ZnSe quantum wires as models, we show that how hole-transfer processes in different SEDs affect their photocatalytic performances. We found that larger driving forces of SEDs monotonically enhance hole-transfer rates and photocatalytic performances by almost three orders of magnitude, a result conforming well with the Auger-assisted hole-transfer model in quantum-confined systems. Intriguingly, further loading Pt cocatalyts can yield either an Auger-assisted model or a Marcus inverted region for electron transfer, depending on the competing hole-transfer kinetics in SEDs.