以ILTO为阳极的高效有机电致发光器件

以高功函数的掺杂钛酸镧的氧化铟薄膜(ILTO)及氧化铟锡(ITO)作为阳极,制备了Glass/anode/NPB/Alq3/LiF/Al结构的有机电致发光器件。得益于ILTO较好的掺杂性、低的表面粗糙度、高的可见光透过率以及高的有效功函数,以ILTO为阳极的有机电致发光器件的开路电压得到降低,最高亮度、电流效率、功率效率以及外量子效率均获得了成倍的提高。研究结果表明,ILTO是一种潜在的光学窗口材料,有望在各种光电器件中得到广泛的应用。     

基于新型透明导电电极的有机光伏器件的制备与表征

介绍了一种高功函数的掺杂钛酸镧的氧化铟透明导电阳极并用其制备了有机光伏器件,详细研究了该材料对器件性能的影响,同时对比了ITO为阳极的器件性能。由于ILTO具有较好的掺杂、较高的透过率和高的有效表面功函数等优异的光电特性,与基于ITO的器件相比,ILTO的有机光伏器件的填充因子、短路电流及功率转换效率均得到了优化与提升,填充因子由61.1%提高到63.5%,短路电流由3.26 mA/cm2提高到5.64 mA/cm2,功率转换效率由0.91%提高到1.45%。     

基于旋涂法和电子束蒸发法制备的V_2O_5/Ag/V_2O_5叠层透明导电薄膜

利用溶胶-凝胶技术与电子束蒸镀相结合的方法在常温下制备了叠层V2O5/Ag/V2O5(VAV)透明导电薄膜,研究了各层薄膜厚度对叠层结构光电特性的影响。用原子力显微镜、紫外-可见光分光光度计、四探针电阻仪及开尔文探针对样品的表面形貌、光电性能及功函数等性质进行了表征。实验结果表明,该薄膜具有良好的光学和电学性质,可见光(380~780 nm)平均透过率达75%,迁移率为16.89 cm2/(V·s),载流子浓度为-1.043×1022cm-3,方块电阻值为15.1Ω/□,功函数为5.17 eV。该制备方法降低了V2O5薄膜的工艺制备难度,为该材料在太阳能电池中的应用创造了良好的前期基础。     

IPTO薄膜制备及其在有机光电器件中的应用

新型IPTO(Pr Ti O3掺杂In2O3)薄膜的可见光透过率及导电性可与商业化的ITO薄膜媲美。采用双源电子束设备制备了一种新型的IPTO透明导电薄膜,通过开尔文探针法测试,其功函数为5.14 e V。为验证新型IPTO透明导电阳极对有机电致发光器件性能的影响,将IPTO替代商业化ITO作为阳极制备了有机电致发光器件。基于IPTO阳极的器件的亮度最大值为85 140 cd/m2,外量子效率最大值为3.16%,分别为以ITO为阳极的器件的3倍及1.13倍。这种性能的改善是由于IPTO具有较小的表面粗糙度及较高的功函数,可以降低阳极的注入势垒,有利于电荷向有机层注入,改善了器件内的空穴及电子的注入平衡。     

透明导电铟铋氧化物薄膜的制备及其性能

以氧化铟为主体材料,以铋为掺杂材料,采用真空热蒸发方法研制出2.5%铋掺杂的透明导电氧化物薄膜(IBO)。实验表明:IBO薄膜具有良好的表面形貌,载流子浓度为3.955×1019cm-3,载流子迁移率达到50.21cm2·V-1·s-1,电导率为3.143×10-3Ω·cm,在可见光范围内的平均透过率超过82%,功函数为4.76eV。采用其作为阳极制作的OLED得到最大亮度30230cd/m2,最大电流效率为5.1cd/A。结果表明IBO是一种良好的光电器件阳极材料。     

ZnO薄膜肖特基二极管的研制

采用直流反应磁控溅射的方法,在Al/Si(100)衬底上沉积了ZnO晶体薄膜.利用Al和Pt作为与ZnO接触的欧姆电极与肖特基电极,制作了ZnO薄膜肖特基二极管.X射线衍射测试结果表明ZnO薄膜具有高度的c轴择优取向.原子力显微分析表明:样品表面光洁平整,晶粒尺寸约100nm,扩展电阻分析表明ZnO薄膜的厚度为0.4μm,载流子浓度为1.8×1015 cm-3,此后的霍尔测试证实了这一结果并说明ZnO的导电类型为n型.室温下的I-V测试显示ZnO肖特基二极管具有明显的整流特性.Pt与n型ZnO接触的势垒高度为0.54eV.文中的ZnO肖特基二极管为首次研制的原型器件,其性能可以通过器件结构与制作工艺的进一步优化而得到改善.     

在c-面蓝宝石上控制生长高质量的ZnO单晶薄膜

利用Mg O和低温Zn O的缓冲层技术,在c面蓝宝石衬底上用等离子体辅助分子束外延(P-MBE)的方法生长了高质量的Zn O单晶薄膜。通过XRD测试,Zn O薄膜样品具有c轴方向的择优取向,其(002)方向摇摆曲线的半高宽(FWHM)仅为68.4 arcsec,(102)方向摇摆曲线的半高宽(FWHM)为1 150 arcsec,显示了外延薄膜极高的晶体质量。另外从扫描电子显微测试结果和原子力显微测试结果来看,Zn O薄膜具有极为平整的表面,3μm×3μm面积内的均方根粗糙度仅为0.842 nm,接近原子级的平整。拉曼光谱(Raman)和荧光光谱(PL)测试结果显示,Zn O薄膜样品内部的应力基本释放,而且具有极低的点缺陷密度。高质量Zn O单晶薄膜的实现为Zn O基的光电器件的制备提供了坚实的基础。     

基于旋涂法和电子束蒸发法制备的V2O5/Ag/V2O5叠层透明导电薄膜

利用溶胶-凝胶技术与电子束蒸镀相结合的方法在常温下制备了叠层V₂O₅/Ag/V₂O₅（VAV）透明导电薄膜,研究了各层薄膜厚度对叠层结构光电特性的影响。用原子力显微镜、紫外-可见光分光光度计、四探针电阻仪及开尔文探针对样品的表面形貌、光电性能及功函数等性质进行了表征。实验结果表明,该薄膜具有良好的光学和电学性质,可见光（380~780 nm）平均透过率达75%,迁移率为16.89 cm²/（V·s）,载流子浓度为－1.043×10²² cm^-3,方块电阻值为15.1 Ω/□,功函数为5.17 eV。该制备方法降低了V₂O₅薄膜的工艺制备难度,为该材料在太阳能电池中的应用创造了良好的前期基础。     

基于接触势差法的表面功函数测试装置

利用接触势差法自行设计开发了一种新型的表面功函数测试装置。基本原理是参考电极与样品之间形成电容,计算流过参考电极与样品之间的电流,通过确定电流的零点来获得功函数。此测量仪器由函数发生、功率放大、振荡器等多个功能模块组成。能在空气环境中快速测量半导体、金属、金属氧化物薄膜的表面功函数。我们运用此装置成功地对有机电致发光的阳极氧化铟锡(ITO)薄膜、p型硅片的功函数进行了测量,得到了样品经过UV-Ozone处理前后功函数随时间变化的曲线,为器件的优化提供了依据。     

肖特基钙钛矿太阳电池结构设计与优化

有机-无机杂化钙钛矿材料有高吸收系数、低廉的制作成本以及较为简单的制备工艺,在近年来表现出良好的发展前景.本文采用wx-AMPS模拟软件对平面结构钙钛矿太阳电池和肖特基钙钛矿太阳电池进行建模仿真对比,从理论上分析无载流子传输层的肖特基钙钛矿太阳电池的优势.结果显示,器件两侧电极功函数和吸收层的能带分布是提高太阳电池效率的关键.在对电极使用Au(功函数为5.1 eV)的前提下,透明导电电极功函数为3.8 eV,可以得到肖特基钙钛矿太阳电池转换效率为17.93%.对器件模型吸收层进行优化,通过寻找合适的掺杂浓度,抑制缺陷密度,确定合适的厚度,可以获得理想的转换效率(20.01%),是平面异质结结构(理论转换效率31%)的63.84%.肖特基钙钛矿太阳电池在简单的器件结构下可以获得优异的光电性能,具有较好的应用潜力.     

Photoluminescence studies on porous silicon/polymer heterostructure

Hybrid devices formed by filling porous silicon with MEH-PPV or poly [2-methoxy-5(2-ethylhexyloxy-p-phenylenevinylene)] have been investigated in this work. Analyses of the structures by scanning electron microscopy (SEM) demonstrated that the porous silicon layer was filled by the polymer with no significant change of the structures except that the polymer was infiltrated in the pores. The photoluminescence (PL) of the structures at 300 K showed that the emission intensity was very high as compared with that of the MEH-PPV films on different substrates such as crystalline silicon (c-Si) and indium tin oxide (ITO). The PL peak in the MEH-PPV/porous silicon composite structure is found to be shifted towards higher energy in comparison with porous silicon PL. A number of possibilities are discussed to explain the observations.     

Tunable photoluminescence and electroluminescence of size-controlled silicon nanocrystals in nanocrystalline-Si/SiO2 superlattices

We present photoluminescence and electroluminescence of silicon nanocrystals deposited by plasma-enhanced chemical vapor deposition (PECVD) using nanocrystalline silicon/silicon dioxide (nc-Si/SiO₂) superlattice approach. This approach allows us to tune the nanocrystal emission wavelength by varying the thickness of the Si layers. We fabricate light emitting devices (LEDs) with transparent indium tin oxide (ITO) contacts using these superlattice materials. The current-voltage characteristics of the LEDs are measured and compared to Frenkel-Poole and Fowler-Nordheim models for conduction. The EL properties of the superlattice material are studied, and tuning, similar to that of the PL spectra, is shown for the EL spectra. Finally, we observe the output power and calculate the quantum efficiency and power conversion efficiency for each of the devices.     

Si-based erbium-doped light-emitting devices

We report on the fabrication and performance of Si-based light sources. The devices consist of MOS structures with erbium (Er)-doped silicon rich oxide (SRO) film as gate dielectric. The devices exhibit electroluminescence (EL) at 1.54 μm at room temperature with a 0.2% external quantum efficiency. These devices show a high stability due to the silicon excess in the film. The Er-doped SRO films have been introduced in a Si/SiO₂ Fabry-Perot Microcavity in order to increase the spontaneous emission rate, the extraction efficiency and the spectral purity at the resonant wavelength. The active medium in the cavity has been electrically pumped and the conduction mechanisms have been analyzed. The EL spectra have also been acquired and compared with photoluminescence (PL) ones for the same resonant cavity light-emitting device (RCLED). The EL and PL peak intensities of the on-axis emission at the resonant wavelength are over 20 times above that of the similar Er-doped SRO film without a cavity. The Si-based RCLEDs exhibit different quality factors, ranging from 60 to 170. The spectra shape and intensity have been correlated with the quality factor. A high directionality of the emitted light, due to the presence of the resonant cavity, has also been observed: the overall luminescence is confined within 10° cone from the sample normal.     

Photoluminescence characterization of few-nanocrystals electronic devices

Photoluminescence (PL) spectroscopy is demonstrated as a suitable technique to characterize silicon nanocrystals (Si-NCs)-based non-volatile memory devices. The 2D array of Si-NCs forming the floating gate is obtained by low-energy ion implantation in thin oxide followed by annealing. The electrical properties and PL emission are dramatically improved after annealing in oxidizing conditions, which are necessary conditions for oxide healing. Both these elaboration and characterization techniques are currently extended to the production and the study of nanoscale electronic devices, which exploit the Coulomb blockade effect and other quantized charging features at 300 K. The fabrication of such devices requires the fine control of a small number of NCs of about 3 nm in diameter. This could be achieved by 1 keV Si-implantation through stencil masks with window sizes ranging from about 0.1 to 10 μm², with spacing between apertures in the 1-10 μm range. After mask removal and annealing, PL spectroscopic imaging under a confocal microscope is used to detect the NCs rich areas. The image of the PL intensity is found to mimic the mask geometry. Some changes of the PL energy at maximum intensity are found, that could be attributed to different Si-NCs sizes.     

钙钛矿型氧化物透明导电薄膜La:SrTiO_3的制备、结构与物性研究

本文采用脉冲激光沉积法于不同沉积温度与衬底制备了一系列的La0.05 Sr0.95 TiO3(LSTO)单晶透明导电薄膜.实验主要研究了高温高氧压条件下沉积的LSTO薄膜的结构及电、光学性质.它们具有良好的外延结构,表现出很好的透明、导电性质.对电阻率拟合发现其导电机制符合电子.电子散射机制.由于制备条件与其它多种钙钛矿型氧化物薄膜一致,可广泛集成应用.用其作为电极所制备的PbZr0.52 Ti0.48O3(PZT)外延铁电电容器,具有很好的电滞回线和透光性.     

Review of flexible and transparent thin-film transistors based on zinc oxide and related materials

Flexible and transparent electronics enters into a new era of electronic technologies.Ubiquitous applications involve wearable electronics,biosensors,flexible transparent displays,radio-frequency identifications(RFIDs),etc.Zinc oxide(ZnO) and relevant materials are the most commonly used inorganic semiconductors in flexible and transparent devices,owing to their high electrical performances,together with low processing temperatures and good optical transparencies.In this paper,we review recent advances in flexible and transparent thin-film transistors(TFTs) based on ZnO and relevant materials.After a brief introduction,the main progress of the preparation of each component(substrate,electrodes,channel and dielectrics) is summarized and discussed.Then,the effect of mechanical bending on electrical performance is highlighted.Finally,we suggest the challenges and opportunities in future investigations.     

Highly uniform electrochromic tungsten oxide thin films deposited by e-beam evaporation for energy saving systems

In the last few decades, there has been a surge of interest in using tungsten oxide thin films as an active layer of electrochromic device. These devices have several practical applications such as smart window of buildings and automobile glazing for energy saving. The main objective of this work was to construct highly homogeneous and uniform e-beam evaporated amorphous WO_3-x based films into electrochromic devices, which were fully characterized for switching speed, coloration efficiencies and cycling voltammetry responses. Fabricated devices contain indium doped transparent oxide coated glass as the transparent conductive electrode, ～200?nm thickness of WO_3-x as the cathodically coloring material and a lithium perchlorate based conducting gel electrolyte. X-ray diffraction patterns indicate that all as-deposited films are amorphous. Experimental results showed that both solid and liquid electrolyte electrochromic devices are initially very transparent that exhibit perfect optical modulation and coloration efficiency (up to 68.7?cm²/C and 52.6?cm²/C at 630?nm, respectively) due to easier intercalation of the Li⁺ within their structure. One of the more significant findings to emerge from this study is that e-beam coated electrochromic devices based on tungsten oxide thin films showed superior performance among to other coating methods. Therefore, excellent reversibility of color change behavior is attractive for pertinent use in electrochromic energy storage devices.     

Absolute work function measurement by using photoelectron spectroscopy

Work function (WF) of a material is not only an intrinsic characteristic of bulk but also a surface property. The measurement and control of WF have been of great concern in many electronic and optical devices as the WF governs charge transfer and charge injection/collection efficiency at interfaces and emission characteristics of conventional charged particle emitters. Photoelectron spectroscopy (PES) has been mainly used to determine surface electronic structure and chemical composition. Despite the common use of this technique to measure WF, there has been a lack of discussion on how to use the PES and what to be considered to determine the absolute WF. The main contribution of this review lies in the discussion of the causes of errors when measuring WF, and provides a guide for reliable WF measurement. Along with the limitations of current measurement technology, we propose future directions for absolute WF measurement.     

Photoluminescence and electroluminescence investigations at Ge-rich SiO2 layers

Strong blue and violet photo (PL) and electroluminescence (EL) at room temperature was obtained from SiO₂-films grown on crystalline Si, which were either single (SI) or double implanted (DI) with Ge ions and annealed at different temperatures. The PL spectra of Ge-rich layers reach a maximum after annealing at 500–700°C for DI layers or 900–1000°C for SI layers, respectively. Both, PL and EL of 500 nm thick Ge-rich layers are easily visible by the naked eye at ambient light due to their high intensity. Based on excitation spectra we tentatively interpret the blue PL as due to the oxygen vacancy in silicon dioxide.

The EL spectrum of the Ge-implanted oxide correlates very well with the PL one and shows a linear dependence on the injected current over three orders of magnitude. For DI layers much higher injection currents than for SI layers can be achieved. An EL efficiency in the order of 10⁻⁴ for Ge⁺-implanted silicon dioxide was determined.