The Effect of Polymer Optoelectronic Properties on the Performance of Multilayer Hybrid Polymer/TiO2 Solar Cells

We report a study of the effects of polymer optoelectronic properties on the performance of photovoltaic devices consisting of nanocrystalline TiO₂ and a conjugated polymer. Three different poly(2‐methoxy‐5‐(2′‐ethylhexoxy)‐1,4‐phenylenevinylene) (MEH‐PPV)‐based polymers and a fluorene–bithiophene copolymer are compared. We use photoluminescence quenching, time‐of‐flight mobility measurements, and optical spectroscopy to characterize the exciton‐transport, charge‐transport, and light‐harvesting properties, respectively, of the polymers, and correlate these material properties with photovoltaic‐device performance. We find that photocurrent is primarily limited by the photogeneration rate and by the quality of the interfaces, rather than by hole transport in the polymer. We have also studied the photovoltaic performance of these TiO₂/polymer devices as a function of the fabrication route and device design. Including a dip‐coating step before spin‐coating the polymer leads to excellent polymer penetration into highly structured TiO₂ networks, as was confirmed through transient optical measurements of the photoinduced charge‐transfer yield and recombination kinetics. Device performance is further improved for all material combinations studied, by introducing a layer of poly(ethylene dioxythiophene) (PEDOT) doped with poly(styrene sulfonic acid) (PSS) under the top contact. Optimized devices incorporating the additional dip‐coated and PEDOT:PSS layers produced a short‐circuit current density of about 1 mA cm^–2, a fill factor of 0.50, and an open‐circuit voltage of 0.86 V under simulated AM 1.5 illumination (100 mW cm^–2, 1 sun). The corresponding power conversion efficiency under 1 sun was ≥ 0.4 %.     

二维非正交坐标斜方格金属光子带隙结构

金属光子带隙结构在高能加速器、微波真空电子器件和太赫兹波源等方面具有重要的应用前景.基于实空间传输矩阵理论，详细研究了非正交坐标系下二维斜方格金属光子带隙结构，给出了计算横电模、横磁模完全带隙结构的一般公式，并分析了填充系数、任意斜角及金属柱横截面对带隙结构的影响.计算结果在退化为正方格情况下时，与其他方法的计算结果取得很好的一致. 关键词： 光子晶体 金属光子带隙 传输矩阵法 微波真空电子器件     

The epitaxial sexiphenyl (0 0 1) monolayer on TiO2(1 1 0): A grazing incidence X-ray diffraction study

A para-sexiphenyl monolayer of near up-right standing molecules (nominal thickness of 30 Å) is investigated in-situ by X-ray diffraction using synchrotron radiation and ex-situ by atomic force microscopy. A terrace like morphology is observed, the step height between the terraces is approximately one molecular length. The monolayer terraces, larger than 20 μm in size, are extended along the [0 0 1] direction of the TiO₂(1 1 0) substrate i.e. along the Ti-O rows of the reconstructed substrate surface. The structure of the monolayer and its epitaxial relationship to the substrate is determined by grazing incidence X-ray diffraction. Extremely sharp diffraction peaks reveal high crystalline order within the monolayer, which was found to have the bulk structure of sexiphenyl. The monolayer terraces are epitaxially oriented with the (0 0 1) plane parallel to the substrate surface (out-of-plane order). Four epitaxial relationships are observed. This in-plane alignment is determined by the arrangement of the terminal phenyl rings of the sexiphenyl molecules parallel to the oxygen rows of the substrate.     

Correlated and non-correlated growth kinetics of pentacene in the sub-monolayer regime

We present a study of the growth kinetics of pentacene monolayer islands on SiO₂ in the submonolayer regime by using Atomic Force Microscopy (AFM). Two distinct growth modes, namely correlated growth (CG) and non-correlated growth (NCG), have been identified by Voronoi tesselation. These two modes are characterized by different island growth kinetics. In the case of correlated growth, the average island size 〈A〉 scales with deposition time t i.e. 〈A〉 ∝ t whereas for non-correlated growth, 〈A〉 ∝ t². The CG and NCG regimes are defined by the level of re-evaporation which determines the capture zones around the islands: Wigner-Seitz cells for CG and coronas of width λ_D (λ_D is the mean diffusion distance on SiO₂ before re-evaporation) for NCG. A simple model is proposed to reproduce the experimental growth kinetics in both modes.     

应用LiNbO_3声表面波驱动的全光纤声光频移器

介绍一种工作在10.7MHz的全光纤声光频移器.它由在LiNbO_3基片上制作的叉指电极换能器产生的声表面波驱动.当驱动电功率1.5W时,频移光转换效率达35％.     

同轴型光电器件的研究开发

本文简要地介绍了武汉电信器件公司正在研究开发的同轴型光电器件，新的器件的工艺与结构特点以及主要技术指标、使用前景。     

Bright Blue Light—emitting Diodes Based on a Novel Fluorescent Dye Containing Heterocyclic Groups

Novel molecular material ,1-benzothiazoly-3-pheny1-pyrazoline (BTPP) was found to function as bright blue light emitting dye in organic electroluminescent device, and its optical and electric characteristics were investigated. This heterovyclic compound exhibited good characteristics of blue photoluminescence and electroluminescence,which had the emission peak at 450nm .The single layer light-emitting devices using BTPP as light -emitting material dispersed in poly(N-vinylcarbazole)(PVK) and double layer ones using PBD as hole block layer above the light-emitting layer were fabricated using conventional spin-casting and vaccum vapour deposition methods. The introduction of PBD has enhanced electron injection and luminance efficiency, compared with the single layer LEDs.     

变频器的选型及配置要点

本文针对应用广泛的通用变频器，提出了在变频器选型和外围配置中需要注意的一些问题。     

Resonant-cavity-enhanced photodetectors and LEDs in the mid-infrared

In this paper we outline the use of resonant-cavity enhancement for increasing the exterior coupling efficiency of photodetectors and light-emitting diodes (LEDs) in the mid-infrared (MIR) spectral region. This method is potentially very important in the MIR because encapsulation is not presently feasible due to the lack of suitable materials. Among other potential applications, resonant-cavity-enhanced (RCE) photodetectors and LEDs could be particularly suitable for greenhouse gas detection because of their ‘pre-tunable’ spectrally narrowed resonantly enhanced peaks. We also present the optical characterization of an InAs RCE photodetector aimed at the detection of methane gas (λ≈3.3 μm), and an InAs/InAs_0.91Sb_0.09 resonant-cavity LED (RCLED) aimed at carbon dioxide gas (λ≈4.2 μm). The high peak responsivity of the RCE photodetector was 34.7 A/W at λ=3.14 μm, and the RCLED peaked at λ=3.96 μm. These are among the longest operating wavelengths for III–V RCE photodetectors and RCLEDs reported in the literature.     

若干具有[(PO4)2Mo5O15]簇骼的化合物的光谱研究

本文对所合成的具有 [(PO4 ) 2 Mo5O1 5]簇骼的 3种新颖的有机 磷钼酸盐簇合物(NH3CH2 CH2 NH3) 2 5[(PO4 ) (HPO4 )Mo5O1 5]·7 5H2 O (Ⅰ ) ,(H3NCH2 CH2 NH3) 3·[(PO4 ) 2 Mo5O1 5]·3H2 O (Ⅱ )和(H3NCH2 CH2 NH3) 2 ·[Cu(en) ][(PO4 ) 2 Mo5O1 5]·5H2 O (Ⅲ )用FTIR ,NIR Raman ,紫外 可见漫反射光谱 (UV VisDRS)和荧光光谱等研究手段 ,对其进行光谱研究 ,探讨其结构和性能的关系。在这些化合物中 ,化合物Ⅰ和Ⅱ具有孤立的 [(PO4 ) 2 Mo5O1 5]簇骼基元 ,而化合物Ⅲ的 [(PO4 ) 2 Mo5O1 5]簇骼基元是由 [Cuen]基团桥联成链 ;磷钼酸盐的特征振动频率和这些化合物的结构相关 ;UV VisDRS显示 ,在 2 0 0和 2 6 0nm左右有两个杂多化合物的特征吸收谱带 ;化合物的稳态荧光光谱中 ,观察到以 2 4 0nm激发 ,在大约 4 0 0nm附近出现的由金属氧簇Oμ→Mo跃迁激发所引起的较强的发射峰 ,在化合物 (Ⅲ )中 ,还观察到通过 [Cuen]的荷移跃迁的以 5 70nm激发所产生的 6 0 4nm的发射峰。