Optimized film processing of nanosilver colloids for photoluminescence enhancement

Recently, various research strategies have been employed to improve light extraction efficiency in organic LEDs, including the recent development of localized surface plasmon resonance (LSPR), as well as the more widely-known application of a photonic crystal layer. Here, we report on the development of a process method for forming a two-dimensional nanosilver patterned array to achieve LSPR-coupled light-emission efficiency enhancement. The process scheme involves the spin-coating of nanosilver colloidal ink onto a glass substrate, followed by optimized thermal annealing to create an array of isolated nanosilver islands. The resulting Ag islands are in the size range 50 approximately 80 nm, which is larger than the diameter of the Ag nanoparticles in the colloidal suspension. Then, silicon oxide is thermally sputtered to provide a spacer layer to prevent luminescence quenching of the red-emitting nanocrystal quantum dot (NQD) layer, which is deposited in a subsequent spin-coating process. When the NQD layer is excited, the energy of the photoelectron is confined to the surfaces of the nanosilver islands in the near-field. In this study, the localized surface plasmon resonance peaks were at a wavelength of 625 nm, and out-coupling efficiency was enhanced more than sixfold.     

真空沉积掺杂制备PARYLENE功能薄膜研究

本文介绍了高分子材料PARYLENE的真空沉积机理及其优越性和不足。提出了一种在PARYLENE真空沉积过程中引入机械掺杂制备具有特定功能的PARYLENE高分子薄膜的方法并给出了掺杂试验设备设计方案。最后提出了影响机械粉体掺杂效果的几个因素。     

基于溶胶-凝胶的两种旋涂方法制备PZT厚膜(英文)

采用溶胶-凝胶法,研究了两种在Au/Cr/SiO2/Si基底上沉积PZT(Pb(Zr0.52Ti0.48)O3)厚膜的方法.把与PZT澄清溶胶成分相同的PZT纳米粉混入澄清PZT溶胶,然后超声混合形成PZT浆料,PZT纳米粉的粒径为50～100nm.XRD分析表明两种方法得到的PZT厚膜都获得了单相钙钛矿结构.SEM结果显示两种厚膜厚度大约4μm,第一种旋涂方法制得的PZT厚膜表面粗糙,第二种旋涂方法制得的厚膜表面致密,无裂纹.在1 kHz的测试频率下,第一种和第二种厚膜的矫顽场分别为30 kV/cm和50 kV/cm,饱和极化分别为45 μC/cm2和54 μC/cm2,剩余极化分别为25μC/cm2 and 30μC/cm2.第二种厚膜有较高的直流耐压性能,在300 kV/cm的电场下,仍然保持较好的铁电性能.因而,第二种旋涂方法能够改善PZT厚膜的表面形貌和铁电性能.     

Fabrication of 380 nm ultra violet light emitting diodes on nano-patterned n-type GaN substrate

380 nm ultraviolet (UV) light emitting diodes (LEDs) were grown on patterned n-type GaN substrate (PNS) with silicon dioxide (SiO2) nano pattern to improve the light output efficiency. Wet etched self assembled indium tin oxide (ITO) nano clusters serves as dry etching mask for converting the SiO2 layer grown on n-GaN template into SiO2 nano patterns by inductively coupled plasma etching. Three different diameter of ITO such as 200, 250 and 300 nm were used for SiO2 nano pattern fabrication. PNS is obtained by n-GaN regrowth on SiO2 nano patterns and UV LEDs were grown on PNS template by MOCVD. Enhanced light output intensity was observed by employing SiO2 nano patterns on n-GaN. Among different PNS UV LEDs, LED grown on PNS with 300 nm ITO diameter showed enhancement in light output intensity by 2.1 times compared to the reference LED without PNS.     

聚3,4-乙烯二氧噻吩/聚苯乙烯磺酸复合LB膜在OLED器件上的应用

采用Langmuir-Blodgett(LB)膜静电诱导沉积法制备聚3,4-乙烯二氧噻吩(PEDOT)高度有序导电聚合物复合薄膜,研究了薄膜的导电性能并进一步研究薄膜在改善器件性能方面的作用.并将其应用于有机电致发光二极管(OLED)器件的空穴缓冲层,将聚3,4-乙烯二氧噻吩/聚苯乙烯磺酸(PEDOT/PSS)复合LB沉积于纳米铟锡金属氧化物(ITO)电极上,制备了以复合LB膜为空穴缓冲层的OLED器件.发现复合LB膜改善了器件性能(启动电压降低,最大亮度增加),但进一步的研究表明LB膜器件在一定时间后出现性能劣化.I-V特性和X射线反射率(XRR)分析表明,薄膜的结构发生一定程度的改变是导致器件性能变差的可能原因.     

镁合金表面微弧氧化-SiO2复合膜层的微观结构和耐蚀性

采用有机醇盐水解法制备SiO2溶胶,用浸溃-提拉制膜技术在AZ31B镁合金微弧氧化陶瓷层表面制备SiO2膜层,研究了镁合金表面微弧氧化-SiO2复合膜层的微观结构和耐蚀性.结果表明:SiO2溶胶进入微弧氧化陶瓷层表面的微孔并形成了SiO2膜层;由微弧氧化陶瓷层和SiO2膜层组成的复合膜层的腐蚀电位比单一陶瓷层明显提高,...     

Experimental study of the organic light emitting diode with a p-type silicon anode

We have fabricated and studied an organic light emitting diode (OLED) with a p-type silicon anode and a SiO₂ buffer layer between the anode and the organic layers which emits light from a semitransparent top Yb/Au cathode. The luminance of the OLED is up to 5600 cd/m² at 17 V and 1800 mA/cm², the current efficiency is 0.31 cd/A. Both its luminance and current efficiency are much higher than those of the OLEDs with silicon as the anodes reported previously. The enhancement of the luminance and efficiency can be attributed to an improved balance between the hole- and electron-injection through two efficient ways: 1) restraining the hole-injection by inserting an ultra-thin SiO₂ buffer layer between the Si anode and the organic layers; and 2) enhancing the electron-injection by using a low work function, low optical reflectance and absorption semitransparent Yb/Au cathode.     

Effect of the plasma treatment of anode electrode of the organic light-emitting diodes on the growth of hole-injection layer

In this paper, we focused on the effects of the plasma treatment of the anode electrode of organic light emitting diodes (OLED) on the growth of hole-injection layer (HIL). The CF₄ plasma (CF₄-P) treatment, which is known for efficient method to enhance the performance of OLED, was not effective on the OLED with the HIL material copper phthalocyanine (CuPc). The CF₄-P treated OLED showed remarkably reduced electroluminescence (EL) characteristics while the O₂ plasma treated OLED showed improved EL efficiency. The dependence of the CuPc growth on the polarity of substrate induced the morphological difference of the HIL, and finally resulted in the different device characteristics.     

The preparation of porous perovskite membranes using BaTiO3 nanopowders

The aim of this study was to develop a simple and reliable procedure in order to prepare composite membranes through the deposition of thin porous layers of perovskite-like oxides onto ceramic porous supports. BaTiO₃ nanopowders with controlled properties were obtained by Low Temperature Aqueous Synthesis (LTAS) and used as starting materials for the thin film deposition. Process parameters were determined in order to obtain a stable suspension of the nanopowder. The nanopowder was then effectively used to realize the layers with controlled properties. The results of characterisation tests indicated that the porosity of the deposited layers was of a mesoporous type and that the starting nanopowder did not undergo structural changes after the deposition process.     

Bi-layer gravure printed nanoscale thick organic layers for organic light emitting diode

The gravure printed single layer structure and bi-layer structure of MEH-PPV/rubrene organic light emitting diodes (OLEDs) were investigated in this work. Typically, the formation of bi-layers in polymer light emitting diodes (PLEDs) is challenging. The brightness and efficiency polymer light emitting materials were enhanced by the gravure printed bi-layer structure in this work. The layer structure of the OLED devices was glass/ITO/PEDOT:PSS/active layer/LiF/Al. The active layers were made using two different processes-one was a gravure printed single organic layer made of a blended mixture of MEH-PPV and rubrene, and the other was a gravure printed bi-layer of MEH-PPV and rubrene. The gravure printed bi-layer devices exhibited a higher brightness and efficiency than the blended devices. The efficiency of the bi-layer MEH-PPV/rubrene structure was improved by a factor of 1.6 approximately 3.2, and the brightness was improved by a factor of 1.9 approximately 2.0 compared to the blended single layer structure. This work demonstrated that organic bi-layers could be formed using gravure printing technology and the bi-layer structure exhibited a higher efficiency than the blended single layer structure.     

MWCNT-polymer composites as highly sensitive and selective room temperature gas sensors

Multi-walled carbon nanotubes (MWCNTs)-polymer composite-based hybrid sensors were fabricated and integrated into a resistive sensor design for gas sensing applications. Thin films of MWCNTs were grown onto Si/SiO(2) substrates via xylene pyrolysis using the chemical vapor deposition technique. Polymers like PEDOT:PSS and polyaniline (PANI) mixed with various solvents like DMSO, DMF, 2-propanol and ethylene glycol were used to synthesize the composite films. These sensors exhibited excellent response and selectivity at room temperature when exposed to low concentrations (100 ppm) of analyte gases like NH(3) and NO(2). The effect of various solvents on the sensor response imparting selectivity to CNT-polymer nanocomposites was investigated extensively. Sensitivities as high as 28% were observed for an MWCNT-PEDOT:PSS composite sensor when exposed to 100 ppm of NH(3) and - 29.8% sensitivity for an MWCNT-PANI composite sensor to 100 ppm of NO(2) when DMSO was used as a solvent. Additionally, the sensors exhibited good reversibility.     

氧化锌/二氧化硅复合膜的结构色研究

采用静电自组装技术,以氧化锌（ZnO）和二氧化硅（SiO2）溶胶颗粒为前驱体,通过控制双组分膜层的不同厚度,制备出结构色鲜艳的ZnO/SiO2复合膜,并利用分光测色仪、多角度分光光度仪及扫描电子显微镜等研究复合膜的颜色、微观结构和形态特征。研究结果发现,ZnO/SiO2复合膜的亮度和色度均较单一组分薄膜的高,复合薄膜的颜色仍随厚度和观察角度的变化而变化。通过对薄膜的微观结构分析,结合其厚度随周期数的变化规律,发现复合薄膜的厚度随着自组装循环次数的增加而增加,薄膜中的纳米粒子并没有形成明显的高低折射率交替分布的双层结构,可能形成的是高折射率层（H层）、有效折射率层（eff层）和低折射率层（L层）的多层微观结构。这种特殊的多层结构与光作用发生干涉,形成了鲜亮度和饱和度更高的结构色。     

热处理温度对TiO2/SiO2复合气凝胶光催化性能的影响

采用溶胶–凝胶法在常压下经不同温度热处理制备了TiO2/SiO2复合气凝胶光催化剂,利用XRD、TGA和BET等手段对其微观结构进行表征,以甲基橙溶液光催化降解实验评价其光催化性能,研究了热处理温度对TiO2/SiO2复合气凝胶的微观结构及光催化性能影响规律.结果表明:随着热处理温度升高,TiO2/SiO2复合气凝胶中锐钛矿结晶度升高,晶粒尺寸增大,比表面积减小,使TiO2/SiO2复合气凝胶对甲基橙溶液的光催化降解活性呈现先升后降的变化趋势.当热处理温度为700℃左右,紫外光照20 min TiO2/SiO2复合气凝胶对甲基橙溶液的降解率达到95.4%.     

Preparation,characterization and photocatalytic activity of TiO<Subscript>2</Subscript> / Methylcellulose nanocomposite films derived from nanopowder TiO<Subscript>2</Subscript> and modified sol–gel titania

TiO₂—methylcellulose (MC) nanocomposite films processed by the sol-gel technique were studied for phocatalytic applications. Precalcined TiO₂ nanopowder was mixed with a sol and heat treated. The sol suspension was prepared by first adding titanium tetra isopropoxide (Ti(OPr)₄ or TTP) to a mixture of ethanol and HCl (molar ratio TTP:HCl:EtOH:H₂O = 1:1.1:10:10) and then adding a 2 wt.% solution of methylcellulose (MC). The TiO₂ nanopowder was dispersed in the sol and the mixture was deposited on a microscope glass slide by spin coating. Problems of film inhomogeneity and defects which caused peeling and cracking during calcinations, because of film shrinkage, were overcome by using MC as a dispersant. Effect of MC on the structure evaluation, crystallization behavior and mechanical integrity with thermal treatment up to 500 °C are followed by SEM, XRD and scratch test. XRD Scanning electron microscopy (SEM) showed that the composite films with MC have much rougher surface than films made without MC. Composite films heat treated at approximately 500 °C have the greatest hardness values. For the composite thick film, the minimum load which caused the complete coating removal was 200 g/mm², an indication of a strong bond to the substrate. Photocatalytic activities of the composite film were evaluated through the degradation of a model pollutant, the textile dye, Light Yellow X6G (C.I. Reactive Yellow 2) and were compared with the activity of (i) a similar composite film without MC, and (ii) a TiO₂ nanopowder. The good mechanical integrity make this composite film an interesting candidate for practical catalytic applications.     

Improved performance of the single-layer and double-layer organic light emitting diodes by nickel oxide coated indium tin oxide anode

The electrical and optical properties of the NiO films deposited under various conditions were first characterized. An ultra-thin layer of nickel oxide (NiO) was then deposited on the indium-tin oxide (ITO) anode to enhance the hole injection in the organic light-emitting diode (OLED) devices. A very low turn-on voltage (3 V) was actually observed for the device with the ITO/NiO anode in the conventional double layer heterojunction OLEDs. The enhancement of hole injection by the ITO/NiO anode was further verified by the hole-only device and by the device with a patterned NiO layer on the ITO anode. The luminance and the current density of the single-layer OLED device were also significantly improved by using the ITO/NiO anode to enhance the hole injection. Although the luminescence efficiency was low, the reasons of low efficiency were studied and the improvement method was proposed. Our results suggest that the NiO/ITO anode is an excellent choice to enhance the hole injection in OLED devices.     

Thin-type integral imaging method with an organic light emitting diode panel

A thin and lensless two-dimensional (2D) to three-dimensional (3D) convertible display based on integral imaging using an organic light emitting diode (OLED) panel as a direct emissive light source is proposed with improved optical efficiency. A point light source array for 2D-3D convertible display is formed on the surface light source, i.e., the OLED panel. However, a blurring effect and color separation result from the finite (nonzero) size of point light sources since each point light source is generated by a pixel of the OLED panel. Simulation results for a blurring effect and color separation in terms of rays from a light source with finite size is presented. The proposed system has a thin structure and simple convertibility because it does not need any additional optical element to provide 2D-3D convertibility.     

Synthesis of green emitting and transparent zn2siO4:mn2+ thin film phosphors on 2D photonic crystal patterned quartz substrates

Zn2SiO4:Mn2+ thin film phosphors (TFPs) have been synthesized by RF magnetron sputtering, using a single multicomponent stoichiometric target. And 2D photonic crystal patterns were introduced on a quartz substrate to enhance the light extraction efficiency. In order to introduce 2D photonic crystal patterns on a quartz substrate, nanosphere lithography was used. Polystyrene spheres, with diameter of 330 nm, were transferred on the quartz substrate and subsequently were served as an etch mask. Quartz substrates were patterned by CF4 gas-based reactive ion etching. Zn2SiO4:Mn2+ were deposited on that 2D photonic crystal patterned quartz substrate and the effect of height of photonic crystal layers were investigated. The light extraction efficiency of Zn2SiO4:Mn2+ thin film phosphors deposited on the photonic crystal patterned quartz substrate was enhanced three times to compared with that of flat Zn2SiO4:Mn2+ thin film phosphors due to the Bragg diffraction and leaky mode caused by PCLs. Transmittance of Zn2SiO4:Mn2+ TFPs deposited on the photonic crystal patterned substrate was high enough, above 70% in the visible light region with respect to that of quartz substrate.     

High efficiency GaN-based light-emitting diodes with embedded air voids/SiO2 nanomasks

In this paper, the high performance GaN-based light-emitting diodes (LEDs) with embedded microscale air voids and an SiO(2) nanomask by metal-organic chemical vapor deposition (MOCVD) were demonstrated. Microscale air voids and an SiO(2) nanomask were clearly observed at the interface between GaN nanorods (NRs) and the overgrown GaN layer by scanning electron microscopy (SEM). From the reflectance spectra we show strong reflectance differences due to the different refractive index gradient between the GaN grown on the nanotemplate and sapphire. It can increase the light extraction efficiency due to additional light scattering. The transmission electron microscopy (TEM) images show the threading dislocations were suppressed by nanoscale epitaxial lateral overgrowth (NELOG). The LEDs with embedded microscale air voids and an SiO(2) nanomask exhibit smaller reverse-bias current and large enhancement of the light output (65% at 20 mA) compared with conventional LEDs.     

预歧化处理的高性能锂离子电池SiO/C负极材料

以SiO和蔗糖为原料,SiO经高温歧化反应处理后,通过机械球磨、喷雾干燥、高温热解工艺制备出具有优异电化学性能的锂离子电池SiO/C负极材料。经XRD、FTIR、XPS、SEM、TEM结构分析表明,歧化反应处理的片状SiO包含非晶态SiO和纳米晶相Si、SiO_2,蔗糖热解形成的无定形碳包覆在细片状SiO的表面,组成球形SiO/C颗粒。电化学测试结果表明,预歧化处理的SiO/C复合材料的首次放电容量为1 314.6mAh/g,首次库伦效率达到71%;100周循环后的放电容量为851.2mAh/g,容量保持率达到78.5%,循环稳定性远高于未经歧化处理的SiO/C复合材料。电化学性能的提高归因于SiO预歧化反应及热解碳包覆。     

SiO2／TiO2复合薄膜光催化性能的研究

采用溶胶-凝胶法和浸渍提拉法在玻璃表面镀制了SiO2/TiO2复合薄膜,以SEM,XPS,UV-Vis等手段对其进行了表征;通过对亚甲基蓝的降解反应,研究了SiO2/TiO2复合薄膜在紫外光下的光催化性能。结果表明:在玻璃片上预镀SiO2层使TiO2薄膜中的Na 和Mg2 含量明显降低,同时,有利于TiO2薄膜中晶粒的长大,提高了光催化性能。