纳米银线柔性透明导电薄膜的制备与研究进展

纳米银线因具有优异的光电性能和机械性能,使其有望在柔性透明导电薄膜领域成为ITO的替代材料。简述了纳米银线柔性透明导电薄膜的结构和基本性质,重点介绍了近年来制备纳米银线柔性透明导电薄膜的几种方法,简单分析了纳米银线柔性透明导电薄膜的应用研究进展和目前该领域研究中所面临的问题。最后,对纳米银线柔性透明导电薄膜的应用前景和发展方向进行了展望。     

纳米银线柔性透明导电薄膜研究进展

随着时代的发展,柔性电子产品的应用越来越广。柔性透明导电薄膜是柔性电子器件中的重要组成部分,由于氧化铟锡并不适合应用到柔性电子器件中,寻找新一代材料引起了研究者的广泛关注。纳米银线作为一种新型的纳米材料,在纳米尺度上有很多新奇的性能,其优良的导电性及良好的光学性能被认为是替代氧化铟锡的最佳材料。本文主要综述了纳米银线柔性导电薄膜的研究进展,主要包括纳米银线导电油墨的物化性能、纳米银线柔性透明导电薄膜的常用制备方法以及主要应用领域。此外,还结合国内外纳米银线柔性透明导电膜的研究现状,指出该研究方向仍存在的一些挑战。     

柔性透明导电薄膜ZAO

随着电子器件向小型化和轻便化方向发展,柔性衬底的透明导电薄膜有望成为硬质衬底透明导电薄膜的更新换代产品,因此其研究备受关注.柔性透明导电薄膜ZAO具有优异的光电性能且资源丰富、成本低、对环境无污染,成为当前的研究热点.总结了近年来对柔性衬底材料处理的方法,介绍了柔性透明导电薄膜ZAO的结构和光电特性.评述了柔性ZAO薄膜的研究现状,并对其近期研究和应用工作做了展望.     

掺Al ZnO柔性透明导电薄膜研究进展

柔性透明导电薄膜ZAO具有优异的光电性能且资源丰富、成本低、对环境无污染,成为当前的研究热点.总结了近年来对柔性衬底材料处理的方法,分析了柔性透明导电薄膜的研究历史和现状.介绍了柔性透明导电薄膜ZAO的结构、光电特性、典型制备方法和应用前景.评述了柔性ZAO薄膜的研究现状,并对其近期研究和应用工作进行了展望.     

ITO/Al复合透明导电薄膜对紫外LED光电性能的提升

通过在氧化铟锡(ITO)薄膜上蒸镀金属Al,获得ITO/Al复合透明导电薄膜,研究了不同退火条件下不同Al金属层厚度的复合透明导电薄膜的方块电阻和在紫外波段的透过率。结果表明,在ITO薄膜上蒸镀2 nm厚的Al层,经550℃退火后,金属Al在ITO薄膜上形成粒径约为10 nm的颗粒,增加了薄膜表面的粗糙度,得到的复合透明导电薄膜的方块电阻和在紫外波段透过率的综合性能最佳,在360～410 nm波长的平均透过率大于95%,且方块电阻为22.8Ω/□。采用ITO/Al(100 nm/2 nm)复合透明导电薄膜制备了390 nm紫外发光二极管(LED)芯片(尺寸为325μm×275μm),与用ITO薄膜制备的LED芯片相比,其光电转换效率提升了约3%,饱和电流提升了15.00%,饱和光功率提升了15.04%。研究结果表明,采用ITO/Al复合透明导电薄膜可有效提升紫外LED的光电性能。     

ITO/Ag/AgNW新型复合透明导电薄膜性能研究

采用磁控溅射和湿法涂布技术制备了一种ITO/Ag/AgNW结构的新型复合透明导电薄膜。研究其光学、电学等性能发现:ITO/Ag/AgNW薄膜在400~700nm的平均透过率高于ITO/Ag/ITO薄膜,且方块电阻远小于ITO/Ag/ITO薄膜,达到6.9Ω/□;耐弯折性能测试后,其方块电阻约增加62%,达11.2Ω/□。研究结果表明,这种新型的复合透明导电薄膜具有低阻、高透及耐弯折良好的特性,在柔性显示领域具有一定的应用潜力。     

柔性ZnS∶Cu电致发光器件制备和性能研究

采用喷墨印制工艺在聚对苯二甲酸乙二醇酯(PET)膜表面制备纳米银线(AgNWs)柔性透明导电膜。以纳米银线柔性透明导电膜分别作为顶电极和底电极，ZnS∶Cu为发光层，聚二甲基硅氧烷(PDMS)为介质层和包装层，采用旋涂工艺制备AgNWs/ZnS∶Cu&PDMS/AgNWs结构的柔性电致发光器件，并研究了电极的光电性能、介质层性能以及施加电压对器件性能的影响。研究表明，良好光电性的电极和高介电常数的介质层有利于提升器件发光强度。当以方阻20Ω/和透光度(550 nm)63.9%的薄膜作为电极，BaTiO₃和PDMS混合作为介质层时，施加200 V电压时器件的发光强度可达2.61 cd·m^-2,施加300 V电压时器件的发光强度可达6.41 cd·m^-2。器件弯曲180°后仍具有良好的电致发光特性。采用喷墨印制工艺制备4 cm×4 cm花朵图案的纳米银线柔性透明导电膜分别作为顶电极和底电极，ZnS∶Cu为发光层，BaTiO₃和PDMS作为介质层和包装层，制备电致发光器件，在200 V(50 Hz...     

GAZO/Ag/GAZO透明导电薄膜的磁控溅射制备及光电性能优化

采用多源磁控溅射技术在玻璃衬底上制备了Ga、Al共掺杂氧化锌(GAZO)/Ag/GAZO透明导电薄膜。对比实验表明，通入O2溅射Ag能够提高薄膜在600～800 nm波段的光透射率。进一步优化后，发现在O2流量为1.0 sccm的条件下，12 nm的Ag获得连续结构，提升了GAZO/Ag/GAZO薄膜的光电性能。在空气中经150℃退火处理1 h,GAZO/Ag/GAZO薄膜的光电性能和结构性能都得到提升。退火后薄膜方块电阻为8.99Ω/sq,380～780 nm可见光波段平均透射率为98.17%，品质因子高达2260Ω^-1。该GAZO/Ag/GAZO透明导电薄膜显示出优异的光电性能，有望替代铟锡氧化物薄膜用于光电器件领域。     

透明导电氧化物薄膜研究现状与产业化进展

综述了 TCO(透明导电氧化物 )薄膜研究开发的历史与现状 ,展望了产业化前景。传统的 ITO薄膜性能优异 ,是重要的平面显示器件用材料。新型 Zn O薄膜成本低廉 ,极具发展潜力 ,有望在太阳能电池领域取代 ITO(掺锡氧化铟 )。多元复合氧化物薄膜是 TCO的发展方向之一 ;柔性衬底的应用扩大了 TCO薄膜的用途 ;溶胶 -凝胶制备工艺的开发促进了大面积 TCO薄膜的实用化     

AZO透明导电薄膜的制备

采用射频磁控溅射法在玻璃衬底上制备了ZnO:Al(AZO)透明导电薄膜,并借助XRD、SEM等表征方法,研究了溅射功率和衬底温度对薄膜结构、表面形貌及光电特性的影响。结果表明,制备薄膜的最佳溅射功率和衬底温度分别为180 W、200℃,在此条件下制备的AZO薄膜具有明显的c轴(002)择优取向,其最低方块电阻为18/□,在可见光范围内的平均透光率超过91%,且透明导电性能优于目前平板显示器的要求,有望取代现在市场上的主流氧化铟锡(ITO)薄膜。     

Modeling the microwave properties of superconductors

In this paper a macroscopic phenomenological model for the microwave properties of superconductors is presented. The model is based on the idea that there are two kinds of current carriers, and instead of the first London's equation a new equation is derived. This model can be applied to both low- and high-temperature superconductors. Using this model, an expression for the microwave surface resistance is derived and the surface resistance versus frequency is calculated. The results show that the relation between resistance and frequency is not R₃~ω² as indicated by both BCS theory and London model, but R_s~ω^a, where a is between 1 and 2 (e.g. a=1.35) for thin film high-T_c superconductors YBa₂Cu₃O_7-δ. The temperature dependence of R_s is simulated using the given model. These relations and the values of the surface resistance agree well with experimental results. A residual resistance may be interpreted from this model     

Results on Punctured Low-Density Parity-Check Codes and Improved Iterative Decoding Techniques

This paper first introduces an improved decoding algorithm for low-density parity-check (LDPC) codes over binary-input-output-symmetric memoryless channels. Then some fundamental properties of punctured LDPC codes are presented. It is proved that for any ensemble of LDPC codes, there exists a puncturing threshold. It is then proved that for any rates R₁ and R₂ satisfying 012<1, there exists an ensemble of LDPC codes with the following property. The ensemble can be punctured from rate R₁ to R₂ resulting in asymptotically good codes for all rates R₁lesRlesR₂. Specifically, this implies that rates arbitrarily close to one are achievable via puncturing. Bounds on the performance of punctured LDPC codes are also presented. It is also shown that punctured LDPC codes are as good as ordinary LDPC codes. For BEC and arbitrary positive numbers R₁2<1, the existence of the sequences of punctured LDPC codes that are capacity-achieving for all rates R₁ lesRlesR₂ is shown. Based on the above observations, a method is proposed to design good punctured LDPC codes over a broad range of rates. Finally, it is shown that the results of this paper may be used for the proof of the existence of the capacity-achieving LDPC codes over binary-input-output-symmetric memoryless channels     

Sensitivity of Rs-measurement of HTS thin films by threeprime resonant techniques: cavity resonator, dielectric resonator, andmicrostrip resonator

The microwave surface resistance, R_s measurement of YBa ₂Cu₃0_{7 -δ} (YBCO) thin film deposited on 10 mm × 10 mm LaAlO₃ substrate using three prime resonating techniques, namely, cavity end plate substitution technique (20 GHz), dielectric resonator technique (18 GHz), and microstrip resonator technique (5 GHz), is reported. In addition, theoretical analysis for each technique has been performed to calculate the relative percentage error in the measured R_s -value of the YBCO thin film as a function of temperature. It has been found that the shielded dielectric resonator provides far better sensitivity for R.-measurement of the YBCO thin film with minimum relative percentage error (<4%) in the temperature range from 20 K to transition temperature of YBCO thin film compared to the other two techniques     

Transparent conductive PVP/AgNWs films for flexible organic light emitting diodes by spraying method

In this study, a simple spraying method is used to prepare the transparent conductive films (TCFs) based on Ag nanowires (AgNWs). Polyvinylpyrrolidone (PVP) is introduced to modify the interface of substrate. The transmittance and bending performance are improved by optimizing the number of spraying times and the solution concentration and controlling the annealing time. The spraying times of 20, the concentration of 2 mg/mL and the annealing time of 10 min are chosen to fabricate the PVP/AgNWs films. The transmittance of PVP/AgNWs films is 53.4%—67.9% at 380—780 nm, and the sheet resistance is 30 Ω/□ which is equivalent to that of commercial indium tin oxide (ITO). During cyclic bending tests to 500 cycles with bending radius of 5 mm, the changes of resistivity are negligible. The performance of PVP/AgNW transparent electrodes has little change after being exposed to the normal environment for 1 000 h. The adhesion to polymeric substrate and the ability to endure bending stress in AgNWs network films are both significantly improved by introducing PVP. Spraying method makes AgNWs form a stratified structure on large-area polymer substrates, and the vacuum annealing method is used to weld the AgNWs together at junctions and substrates, which can improve the electrical conductivity. The experimental results indicate that PVP/AgNW transparent electrodes can be used as transparent conductive electrodes in flexible organic light emitting diodes (OLEDs).     

Ice-Templated,Large-Area Silver Nanowire Pattern for Flexible Transparent Electrode

Flexible transparent electrodes are critically important for the emerging flexible and stretchable electronic and optoelectronic devices. To this end, transparent polymer films coated with silver nanowires (AgNWs) have been intensively studied in the past decade. However, it remains a grand challenge to achieve both high conductivity and transmittance in large-area films, mainly due to the poor alignment of AgNWs and their high junction resistance. Here, the successful attempt to realize large-area AgNW patterns on various substrates by a 2D ice-templating approach is reported. With a relatively low dosage of AgNWs (4 µg·cm⁻²), the resulted flexible electrode simultaneously achieves high optical transmittance (≈91%) and low sheet resistance (20 Ω·sq⁻¹). In addition, the electrode exhibits excellent durability during cyclic bending (≈10 000 times) and stretching (50% strain). The potential applications of the flexible transparent electrode in both touch screen and electronic skin sensor, which can monitor the sliding pressure and direction in real-time, are demonstrated. More importantly, it is believed that the study represents a facile and low-cost approach to assemble various nanomaterials into large-area functional patterns for advanced flexible devices.     

Jointly optimized bit-rate/delay control policy for wireless packetnetworks with fading channels

We consider the downlink rate control problem in a wireless channel. A dynamic programming optimization method is introduced to obtain the optimal bit-rate/delay control policy in the downlink for packet transmission in wireless networks with fading channels. We assume that the base station is capable of transmitting data packets in the downlink with different bit rates, R₀1<···M-1 . It is assumed that the symbol rate is fixed in the system, and different bit rates are achieved by choosing the transmitted symbols from the appropriate signal constellation (adaptive modulation). The derived optimal rate control policy, in each time slot, selects the highest possible bit rate which minimizes the delay and at the same time minimizes the number of rate switchings in the network. The optimal bit-rate control problem is an important issue, especially in packet data networks, where we need to guarantee a quality of service (QoS) in the network. Our analytical as well as simulation results confirm that there is an optimal threshold policy to switch between different rates     

烷基环己基苯类液晶的质谱裂解规律研究

利用气相色谱质谱联用仪(GCMS)对烷基环己基苯、烷基环己基联苯两类液晶单体共72个化合物在EI离子化模式下进行分析,结果表明此两类化合物具有相同的裂解途径和裂解机理。为烷基环己基苯类衍生物的结构解析与质量监测提供参考。其裂解途径主要为与苯环连接的环己烷发生开环裂解反应,生成特征的:苯乙烯(联苯乙烯)基的奇电子离子、苯丙烯(联苯丙烯)基的偶电子离子以及卓鎓偶电子离子。当苯环部分含有乙氧基以上取代基时,分子离子及其特征离子会发生重排脱去烯烃生成对应的苯(联苯)酚离子。对于环己基联苯类化合物在特征离子生成的基础上会进一步生成质量数减少2的脱氢离子。     

All-solution-processed foldable transparent electrodes of Ag nanowire mesh and metal matrix films for flexible electronics

In this study, we developed foldable transparent electrodes composed of Ag nanowire (AgNW) networks welded by Ag nanoparticles (AgNPs) reduced from commercial Ag ink. All the processes used were solution-based. Using the Meyer rod method, uniform AgNW networks were roll-to-roll coated on large-area polymer substrates, and the spin-coated AgNPs firmly welded the AgNWs together at junctions and to substrates. The hybrid films consisting of AgNWs and the Ag film matrix exhibited higher electrical conductivity (5.0–7.3 × 10⁵ S/m) than and equivalent transparency (90–95%) to the AgNW networks. Furthermore, the hybrid films showed significantly better bending stability than AgNW networks. During cyclic bending tests to 10,000 cycles at 5 mm bending radius and even when almost folded with r_b of 1 mm, the resistivity changes were negligible because AgNWs were tightly held and adhered to the substrate by Ag films covering wires, thereby hindering fracturing of AgNWs under tension. Because the films were fabricated at a low temperature, there was no oxidation on the surfaces of the films. Hence, flexible organic light-emitting diodes (f-OLEDs) were successfully fabricated on polyethylene terephthalates (PET) coated with the hybrid films. The f-OLED in the bent state was comparable to that in the flat state, validating the potential applications of these transparent hybrid films as electrodes in various flexible electronics.     

Online rotor resistance estimation using the transient state underthe speed sensorless control of induction motor

In the speed sensorless control of the induction motor, the machine parameters (especially rotor resistance R₂) have a strong influence on the speed estimation. It is known that the simultaneous estimation of the rotor speed and R₂ is impossible in the slip frequency type vector control, because the rotor flux is constant. But the rotor flux is not always constant in the speed transient state. In this paper, the R₂ estimation in the transient state without signal injection to the stator current is proposed. This algorithm uses the least mean square algorithm and the adaptive algorithm, and it is possible to estimate R₂ exactly. This algorithm is verified by the digital simulations and experiments