聚合物MEH-PPV橙红光OLED的研究

以聚合物聚[2-甲氧基-5-(2'-乙烯基-己氧基)聚对苯乙烯撑](MEH-PPV)为发光层,采用旋涂方法制备了两种不同结构的有机电致发光器件(OLED),分别为:ITO/MEH-PPV/Alq3/Mg:Ag和ITO/MEH-PPV/bathocuproine(BCP)/Alq3/Mg:Ag.对两种器件的电致发光谱、J-V曲线和L-V曲线等发光特性进行了分析研究.对比发现,采用BCP为空穴阻挡层的结构具有较大的发光亮度和较高的发光效率.根据能级理论对上述实验结果进行了初步的理论分析,并对器件性能差异的原因进行了解释.     

Electrical properties and barrier modification of GaAs MIS Schottky device based on MEH-PPV organic interfacial layer

We report fabrication and electrical characterization of GaAs based metal-interfacial layer-semiconductor (MIS) device with poly[2-methoxy-5-(2^/-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV), as an interfacial layer. MEH-PPV raises the barrier height in Al/MEH-PPV/p-GaAs MIS device as high as to 0.87 eV. A Capacitance-Voltage (C–V) characteristic exhibits a low hysteresis voltage with an interface states density of 1.69×10¹¹ cm⁻² eV⁻¹. Moreover, a high transition frequency (f_c) of about 50 kHz was observed in the accumulation mode. The photovoltaic response of Al/MEH-PPV/p-GaAs device was measured under the air masses (AM) 1.0 and 1.5. The open circuit voltage (V_OC), short circuit current (I_SC), fill factor and the efficiency of the Al/MEH-PPV/p-GaAs device were found to be 1.10 V, 0.52 mA, 0.65, and 5.92%, respectively, under AM 1.0 condition.     

Influence of the Formation Parameters of Phthalociane:Fullerene Nanocomposite Layer on the Photoelectric Characteristics of ZnPc:C60/C60 Structures

Semiconductors - Abstract—Two approaches are used to form organic photosensitive structures. In the first of these, layered photoactive elements are created, in which active layers are...     

Initial Growth Mode,Nanostructure, and Molecular Stacking of a ZnPc:C60 Bulk Heterojunction

The initial growth modes of ZnPc films is examined, revealing the previously undescribed nanoscale crystal structure evolution and the nanograins of the ZnPc:C60 mixed layers in the thin films. Initially, the ZnPc molecules are stacked in the preferred γ(200) configuration, similar to the structures of CuPc. The ZnPc thin film growth display 2D planar to 3D island growth after the initial compressive strain had relaxed in films 7–8 MLs thick. 3D island formation decreases the prevalence of the preferred ordering in the γ(200) crystals. The ZnPc films consist of randomly distributed ellipsoid nanograins during the initial growth stages. The ellipsoid nanograins transition to an ordered state later in the growth process. Insertion of C60 changes the preferred molecular stacking of ZnPc, and β(100) forms in the ZnPc:C60 layers fabricated at room temperature, which is usually observed at high annealing temperatures (200 °C) in a single ZnPc film. The ellipsoid ZnPc nanograins also retain their shapes in the ZnPc:C60 mixed layers. The formation of β(100) and the presence of ellipsoid nanograins in the mixed layer are related to improvements relative to planar devices in the organic photovoltaic device performance.     

声表面波器件中非同步区域体波散射的抑制

用有限元/边界元法(FEM/BEM)研究了表面波器件中非同步区域中体波散射引起的损耗。以典型的hiccup单端对谐振器作参考结构,用结构参数缓慢变化的间隙取代其中间的自由间隙。研究发现,改变间隙参数可在保持谐振频率不变的同时,提高谐振器的品质因数值。对分布间隙和风琴间隙两种间隙结构进行对比,结果表明,前者优于后者。将传统DMS滤波器中的金属化间隙以分布间隙取代,可找到一个优化的分布间隙结构,使插损提高0.3 dB。     

有机材料MEH-PPV对白光LED光谱特性的影响

分别将质量分数为5、10、15和20%的有机材料MEH-PPV混合加入YAG荧光粉中,观察发光二极管(LED)显色指数的变化。实验结果表明,MEH-PPV在450～550nm区域吸光度逐渐增强,可吸收黄绿光,在615nm附近辐射出较强红光,补充了传统蓝光LED芯片激发YAG荧光粉中缺失的红光成分,使发射带延伸至700nm;当MEH-PPV混合质量分数为15%时,制备的白光LED的显色指数最高,可达到92。随着质量分数从15%持续增加到20%,器件的显色指数开始降低,这是因为LED芯片发出的能量能够激发有机材料MEH-PPV的同时,使MEH-PPV对荧光粉发出的绿光区域有较强吸收,因此存在一个最佳色比使器件的性能达到最佳。     

肖特基器件用重掺As衬底上外延层过渡区控制

掺As衬底外延片很大部分用于肖特基器件,器件对正向压降要求越来越高,因此对外延层参数之一的过渡区宽度提出了更高要求.讨论了影响过渡区的温度、生长速率、本征CAP层以及赶气等因素.通过一系列实验,找到了合理的生长条件,得到了完美的过渡区,解决了器件反向电压和正向压降之间的矛盾.在反向电压一致的条件下,正向压降平均降低了200 mV,产品整体成品率提高了两个百分点以上.研究结果已成功应用于大规模生产中.     

~(60)Coγ射线低能散射对CMOS器件电离辐射效应的影响

在60 Coγ射线辐射场中采用 Pb/ Al屏蔽和非屏蔽的方法 ,研究比较了低能散射对 CMOS器件电离辐射效应的影响。在理论计算基础上 ,设计了 Pb/ Al屏蔽盒。实验结果表明 ,低能散射占总电离辐射吸收剂量的 2 0 %左右 ,采用 Pb/ Al屏蔽盒可以消除低能散射的影响 ,能更可靠地进行微电子器件抗辐射加固水平的精确评估与对比 ;低能散射对 Kovar封装的器件产生剂量增强效应 ,剂量增强因子小于 2 .0     

/sup 60/Co gamma irradiation effects on n-GaN Schottky diodes

The effect of /spl gamma/-ray exposure on the electrical characteristics of nickel/n-GaN Schottky barrier diodes has been investigated using current-voltage (I-V), capacitance-voltage (C-V), and deep-level transient spectroscopy (DLTS) measurements. The results indicate that /spl gamma/-irradiation induces an increase in the effective Schottky barrier height extracted from C-V measurements. Increasing radiation dose was found to degrade the reverse leakage current, whereas its effect on the forward I-V characteristics was negligible. Low temperature (/spl les/50) post-irradiation annealing after a cumulative irradiation dose of 21 Mrad(Si) was found to restore the reverse I-V characteristics to pre-irradiation levels without significantly affecting the radiation-induced changes in C-V and forward I-V characteristics. Three shallow radiation-induced defect centers with thermal activation energies of 88 104 and 144 meV were detected by DLTS with a combined production rate of 2.12 /spl times/ 10/sup -3/ cm/sup -1/. These centers are likely to be related to nitrogen-vacancies. The effect of high-energy radiation exposure on device characteristics is discussed taking into account possible contact inhomogeneities arising from dislocations and interfacial defects. The DLTS results indicate that GaN has an intrinsically low susceptibility to radiation-induced material degradation, yet the effects observed in the Schottky diode I-V and C-V characteristics indicate that the total-dose radiation hardness of GaN devices may be limited by susceptibility of the metal-GaN interface to radiation-induced damage.     

大电流冲击下MEH-PPV对白光LED发光特性的影响

针对用蓝光芯片激发YAG黄色荧光粉实现白光LED的光谱中缺少红色波段成份导致的显色性较差,通过在YAG荧光粉中混合质量分数分别为1%、3%、5%和10%的有机红光材料MEH-PPV,以提高白光LED的显色指数。将制备的白光LED加700mA冲击电流,通过对冲击前后光谱变化的分析结果发现,在大电流冲击下,由于散热不完善,PN结的热阻非常大,导致LED芯片快速老化,并且使有机材料MEH-PPV分解而大量失效;但是对比冲击前后黄光波段的光谱几乎没有变化。这表明,虽然MEH-PPV可以提高器件的显色指数,但是稳定性远不如YAG荧光粉。     

Influence of carrier freeze-out on SiC Schottky junction admittance

Incomplete impurity ionization is investigated in the case of nitrogen donors and aluminum and boron acceptors in 4H and 6H SiC. We calculate the degree of ionization for these impurities residing on different lattice sites in a broad temperature range and for different impurity concentrations. It is shown that the degree of carrier freeze-out is significant in heavily N-doped 6H SiC and in Al- and B-doped SiC. Using the general Schottky junction admittance model we calculate the temperature and frequency dependencies of the junction admittance in the case when impurity ionization by the applied ac bias is present. It is shown that admittance frequency dispersion may be significant at room temperature in the case of N- and B-doped SiC. Finally, we calculate the Schottky junction capacitance as a function of the applied dc bias and simulate the doping profile, using the capacitance-voltage data. The calculated profile is shown to deviate from the actual impurity concentration profile if the impurity ionization time constant is comparable with the ac bias period, which is so for N-and B-doped SiC with certain values of the impurity activation energy and capture cross-section.     

Fabrication and effect of the dielectric permittivity on the ideality factor of MEH-PPV Schottky diodes doped with electron acceptor fluorescent dyes

Polymeric Schottky diodes have been prepared using poly[2-methyl-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) conducting polymers. The I–V characteristics of these diodes are interpreted in terms of thermoionic emission (TIE) conduction process. Upon blending the polymer with Nile blue (NB) dye the conduction shows a cross-over from space-charge limited conduction (SCLC) to TIE at biasing voltages larger than 4 V. Disappearance of SCLC is seen in Rhodamine B (RhB)-based diodes and the conduction is interpreted in terms of the TIE process. Inclusion of the dielectric permittivity of the polymer/dye blends in interpreting the I–V characteristics of diodes is found to be crucial. A significant reduction of the ideality factor (n) from 6 to 1.8 is determined when MEH-PPV is mixed with NB or Rhodamine fluorescent dyes.     

Effect of the Hydrogen Concentration on the Pd/n-InP Schottky Diode Photocurrent

Semiconductors - The variation rate of the short-circuit photocurrent of Pd/n-InP Schottky diodes is studied as a function of the presence of hydrogen in a gas mixture with H2 concentrations of...     

^60Coγ射线低能散射对CMOS器件电离辐射效应的影响

以^60Coγ射线辐射场中采用Pb/Al屏蔽和非屏蔽的方法,研究比较了低能散射对CMOS器件电离辐射效应的影响。在理论计算基础上,设计了Pb/Al屏蔽盒。实验结果表明,低能散射占总电离辐射吸引剂量的20％左右,采用Pb/Al屏蔽盒可以消除低能散射的影响,能更可靠地进行微电子器件抗辐射加固水平的精确评估与对比;低能散射对Kovar封装的器件产生剂量增强效应,剂量增强因子小于2．0.     

碱土族金属掺杂对C60薄膜的电子结构与性质的影响

将Sn粉末和C60粉末共同蒸发获得碱土族金属掺杂的C60薄膜样品，与未掺杂的纯C60样品一起进行扫描电镜，紫外可见吸收光谱和电阻随温度变化特性的测量，分析比较掺杂对薄膜样品的组成，结构和性质的影响，结果显示，掺锡后组成薄膜的纳米颗粒略有增大并突出表面，使薄膜的电子发射阈值降低，掺入的Sn原子在禁带中形成杂质能级，使电子吸收跃迁由原来的直接跃迁变为间接跃迁，导电性也由原来的绝缘体变为N型半导体。     

电荷耦合器件电离辐射损伤的模拟试验研究

利用钴-60源,在不同工作与辐照条件下,开展电荷耦合器件电离辐射损伤模拟试验,分析高低剂量率、器件偏置对器件暗电流信号增大和哑元电压漂移的影响,比较电荷耦合器件光敏单元、输出放大器总剂量效应的敏感性,研究辐射敏感参数与失效模式的差异.为建立电荷耦合器件电离辐射效应规范化的模拟试验与加固评估方法,提供技术基础.     

Efficient Polythiophene/Polyfluorene Copolymer Bulk Heterojunction Photovoltaic Devices: Device Physics and Annealing Effects

Here the influence of annealing on the operational efficiency of all‐polymer solar cells based on blends of the polymers poly(3‐hexylthiophene) (P3HT) and poly((9,9‐dioctylfluorene)‐2,7‐diyl‐alt‐[4,7‐bis(3‐hexylthiophen‐5‐yl)‐2,1,3‐benzothiadiazole]‐2′,2″‐diyl) (F8TBT) is investigated. Annealing of completed devices is found to result in an increase in power conversion efficiency from 0.14 to 1.20%, while annealing of films prior to top electrode deposition increases device efficiency to only 0.19% due to a lowering of the open‐circuit voltage and short‐circuit current. By studying the dependence of photocurrent on intensity and effective applied bias, annealing is found to increase charge generation efficiency through an increase in the efficiency of the separation of bound electron‐hole pairs following charge transfer. However, unlike many other all‐polymer blends, this increase in charge separation efficiency is not only due to an increase in the degree of phase separation that assists in the spatial separation of electron‐hole pairs, but also due to an order of magnitude increase in the hole mobility of the P3HT phase. The increase in hole mobility with annealing is attributed to the ordering of P3HT chains evidenced by the red‐shifting of P3HT optical absorption in the blend. We also use X‐ray photoelectron spectroscopy (XPS) to study the influence of annealing protocol on film interface composition. Surprisingly both top and bottom electrode/blend interfaces are enriched with P3HT, with the blend/top electrode interface consisting of more than 95% P3HT for as‐spun films and films annealed without a top electrode. Films annealed following top electrode deposition, however, show an increase in F8TBT composition to ～15%. The implications of interfacial composition and the origin of open‐circuit voltage in these devices are also discussed.     

Donor–Acceptor C60‐Containing Polyferrocenylsilanes: Synthesis,Characterization, and Applications in Photodiode Devices

A series of polyferrocenylsilane (PFS) random copolymers containing covalently bound pendant [C₆₀]fullerene groups, the first well‐characterized metallopolymers with pendant C₆₀ units, have been prepared and characterized. The fullerene content of the prepared copolymers ranges from 7 to 24% relative to monomer unit. The desired copolymers were synthesized in three steps: metal‐catalyzed ring opening polymerization of sila[1]ferrocenophanes was performed to synthesize random copolymers of poly(ferrocenylmethylphenylsilane‐co‐ferrocenylchloromethylsilane); the resulting random PFSs were then functionalized by reaction with 11‐azido‐1‐undecanol to give PFSs with pendant azide groups; the desired donor–acceptor C₆₀‐containing PFSs were then synthesized by the reaction of the azide group in the side chains with C₆₀ in toluene at 110 °C. The resulting C₆₀‐containing PFSs are air‐stable and soluble in aromatic solvents, chloroform, or THF. The UV‐vis spectra of these materials show broad absorption up to 800 nm. Thin films of these materials were examined as the active layer in rare examples of all solid‐state sandwich‐type diode devices based on ferrocene‐fullerene dyads. The devices exhibit photoconducting and photovoltaic responses, with an open circuit potential of ca. 0.3 V under white light illumination.     

载流子寿命对Si基光电子器件性能的影响

研究了载流子寿命对SOI有源光波导器件工作性能的限制及影响,分析了制约载流子寿命减小的若干因素,综述了采用合理设计减小波导截面尺寸参数、脊区内植入He离子、加入pin结构施加反向偏压等几种有效减少载流子寿命的方法,并给出了它们各自的理论基础和文献报道的理论模拟与实验结果。经过对各种方法的利弊进行分析比较,作者认为在提高光电子器件性能的研究中,采用减小波导截面尺寸参数的方法要同时兼顾传输损耗的变化;采用离子植入法可以在不改变波导尺寸的情况下减小载流子的寿命,但引入了附加损耗且与CMOS工艺不相兼容;而外加pin结构的方法不适用于已经存在电学结构的器件。     

陷阱浓度对ZnS：Mn薄膜电致发光临界浓度和亮度的影响

本文计算了陷阱浓度对ZnS:Mn薄膜电致发光Mn中心临界浓度的影响,在不同的陷阱浓度下,计算了发光亮度随发光中心浓度的变化,计算结果表明：降低陷阱的浓度可以显著地提高临界浓度,并且发光亮度也随之增大。